Final Report of the UNDP Consultants to BRR-NAD-NIAS (May, 2007)

FINAL REPORT UNDP EARTHQUAKE TECHNICAL ADVISORS TO BADAN REKONSTRUKSI DAN REHABILITASI (BRR) NIAS MAY 2007 ________________________________ REPORT PREPARED BY: DICK BEETHAM - EARTHQUAKE ADVISOR/GEOTECHNICAL ENGINEER DJAUHARRY NOOR – SPATIAL PLANNER/ENGINEERING GEOLOGIST BILL SINCLAIR – STRUCTURAL ENGINEER/BUILDING CODE EXPERT ________________________________ UNITED NATIONS DEVELOPMENT PROGRAMME (UNDP) ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 2 of 80 FINAL REPORT UNDP EARTHQUAKE TECHNICAL ADVISORS TO BADAN REKONSTRUKSI DAN REHABILITASI (BRR) NIAS MAY 2007 CONTENTS 1. INTRODUCTION......................................................................................................... 7 1.1 PURPOSE OF CONSULTANCY ASSIGNMENT .................................................. 7 1.2 EARTHQUAKES AND TSUNAMIS OF 26 DECEMBER 2004 AND 28 MARCH 2005 ................................................................................................................................... 8 1.3 DISASTER RISK REDUCTION............................................................................ 10 1.4 BUILDING QUALITY ........................................................................................... 12 1.5 ROLE OF LOCAL GOVERNMENT ..................................................................... 12 2. GEOLOGY OF NIAS ISLAND................................................................................. 15 2.1 PHYSIOLOGY........................................................................................................ 15 2.2 STRATIGRAPHY................................................................................................... 15 2.2.1 Melange Complex............................................................................................ 15 2.2.2 Lelematua Formation....................................................................................... 15 2.2.3 Gomo Formation.............................................................................................. 17 2.2.4 Gunungsitoli Formation................................................................................... 17 2.2.5 Alluvium.......................................................................................................... 17 2.3 GEOLOGY, STRUCTURE, TECTONICS AND GEOLOGICAL HAZARDS OF NIAS................................................................................................................................. 17 2.3.1 Tectonics.......................................................................................................... 17 2.3.2 Structure........................................................................................................... 18 2.3.3 Geological hazards .......................................................................................... 19 2.4 FAULTING ............................................................................................................. 20 2.5 COASTAL UPLIFT AND SUBSIDENCE............................................................. 21 3 SEISMIC HAZARD ASSESSMENT........................................................................ 26 3.1 INTRODUCTION ................................................................................................... 26 3.2 FIELD ASSESSMENTS ......................................................................................... 27 3.2.1 General............................................................................................................. 27 3.2.2 Gunung Sitoli Town ........................................................................................ 27 3.2.3 Sirombu ........................................................................................................... 27 3.2.4 Lotu, Lahewa And Toyolawa .......................................................................... 28 3.2.5 The Road Section Along Idanoi-Gido-Idanogawo.......................................... 29 3.2.6 Teluk Dalam-Bawomataluo-Sorake ................................................................ 29 3.2.7 Tuhemberua ..................................................................................................... 30 3.2.8 Moi And Lolowa’u .......................................................................................... 30 3.2.9 Gomo ............................................................................................................... 30 3.2.10 West Sumatra................................................................................................... 31 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 3 of 80 3.3 THE DESIGN EARTHQUAKE FOR NIAS .......................................................... 31 3.3.1 Introduction ..................................................................................................... 31 3.3.2 DERIVATION OF MAXIMUM PROBABLE EARTHQUAKE................... 32 35 4 DISASTERS RESULTING FROM NATURAL HAZARDS ................................. 36 4.1 WHEN NATURAL HAZARDS BECOME DISASTERS ..................................... 36 4.2 NATURAL HAZARD DISASTER MITIGATION ............................................... 38 4.2.1 General............................................................................................................. 38 4.2.2 Application Of Geology In Land-Use Planning .............................................. 39 4.2.3 Geology-Related Hazard Mapping And Risk Assessment.............................. 39 4.2.4 Early Warning And Management Of Geology Related Hazards .................... 40 4.2.5 Protection Against Geology Related Hazards ................................................. 40 4.2.6 Health Aspects In Natural Hazard Risk Reduction ......................................... 40 4.2.7 Strengthening Institutional Frameworks For Hazard Mitigation .................... 41 4.2.8 Other Aspects Of Natural Hazard Mitigation.................................................. 42 4.3 SUMMARY AND CONCLUSIONS...................................................................... 42 45 5 SEISMIC MICROZONING IN NIAS ...................................................................... 46 5.1 INTRODUCTION ................................................................................................... 46 5.2 PROPOSED MICROZONING FOR NIAS. ........................................................... 46 51 6 CONSTRUCTION QUALITY .................................................................................. 52 6.1 TRADITIONAL HOUSE CONSTRUCTION........................................................ 52 6.2 BUILDING QUALITY PRIOR TO THE EARTHQUAKES OF 26 DECEMBER 2004 AND 28 MARCH 2005.......................................................................................... 54 6.3 ROADS AND BRIDGES........................................................................................ 58 7 BUILDING CODE FRAMEWORK ......................................................................... 68 7.1 INTRODUCTION ................................................................................................... 68 7.2 INDONESIAN BUILDING LEGISLATION ......................................................... 68 7.3 INDONESIAN BUILDING STANDARDS ........................................................... 71 7.4 NIAS BUILDING REGULATIONS....................................................................... 72 8 CONCLUSIONS AND RECOMMENDATIONS.................................................... 74 8.1 DESIGN EARTHQUAKE ...................................................................................... 74 8.2 SPATIAL PLANNING ........................................................................................... 74 8.3 BUILDING DESIGN AND CONSTRUCTION..................................................... 74 8.4 REVISIONS TO NIAS BUILDING REGULATIONS (PERDA).......................... 75 8.5 BUILDING CONSENTS ........................................................................................ 75 8.6 CONSTRUCTION OF CIVIL INFRASTRUCTURE (ROADS, BRIDGES, PORTS, AIRPORTS)....................................................................................................... 78 8.6.1 Bridges............................................................................................................. 78 8.6.2 Roads ............................................................................................................... 78 8.6.3 Gomo Road...................................................................................................... 79 8.6.4 Wharves And Jetties ........................................................................................ 79 8.7 DISASTER PREPAREDNESS............................................................................... 79 APPENDICES ..................................................................................................................... 80 A. MMI DESCRIPTIONS AND INTENSITY SCALE .............................................. 80 B. GOMO ACCESS ROAD REPORT ........................................................................ 80 C. WEST SUMATRA RECONNAISANCE VISIT.................................................... 80 D. POTENTIAL AGGREGATE (SAND, ROCK AND CRUSHED ROCK) SOURCES ON NIAS FORTSUNAMI AND EARTHQUAKE RECONSTRUCTION. 80 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 4 of 80 E. FIELD VISIT REPORT 1-FEB-07 ......................................................................... 80 F. FIELD VISIT REPORT 24-FEB-07 ....................................................................... 80 G. FIELD VISIT REPORT 27-FEB-07 ....................................................................... 80 H. PERATURAN DAERAH KABUPATEN NIAS TINGKAT II NIAS NOMOR 16 TAHUN 1998................................................................................................................... 80 I. PERATURAN BUPATI SLEMAN NOMOR 7/Per.Bup/2006 TENTANG SATUAN PELAKSANAAN PENANGANAN BENCANA, DAN KEPUTUSAN BUPATI SLEMAN NOMOR: 5/Kep.KDH/A/2006 TENTANG RENCANA OPERASIONAL PENANGGULANGAN BENCANA GUNUNG API PERAPI ......... 80 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 5 of 80 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 6 of 80 1. INTRODUCTION 1.1 PURPOSE OF CONSULTANCY ASSIGNMENT The Government of Indonesia-UNDP Project “Technical Support for Badan Rehabilitasi dan Rekonstruksi (BRR) NAD-Nias” was designed to provide BRR with technical support to achieve the following results: • • • • Enhanced technical capacity of the BRR to develop policies and programmes, to appraise proposals submitted by other organizations, and to monitor programme implementation Enhanced operational capacity of the BRR to achieve its mandate in a timely, efficient and transparent manner Enhanced transparency in decision making, and strengthened participation of CBOs, NGOs, the private sector, local government, donors and other stakeholders in planning, implementing and monitoring of reconstruction activities Effective and efficient management, monitoring and oversight of the overall programme on behalf of the Multi-Donor Trust Fund for Aceh and North Sumatra (MDTFANS) donor partners As part of this wider programme three Earthquake Advisors were recruited by UNDP and seconded into the BRR Office in Gunung Sitoli in Nias to provide technical support to BRR in Nias. The Technical Advisors were: • • • Dick Beetham - Engineering Geologist and Geotechnical Engineer (Assignment from 5-Dec-06 until 28-Apr-07) Djauharry Noor - Spatial Planner and Engineering Geologist (Assignment from 7-Jan07 until 6-May-07) Bill Sinclair - Civil/Structural Engineer (Building Code Expert) (Assignment from 7Jan-17 until 10-May-07) Hereinafter referred to as “the Advisors”. The scope of services of the Advisors covered: 1. Geotechnical assessment of ground conditions based on tectonic setting, existing geology and geotechnical data 2. Evaluate the seismic damage assessment of buildings and bridges, in terms of spatial location and construction. 3. Revision of (recommendation for) existing seismic and tsunami hazard assessment based on probabilistic methods. 4. Review requirements for detailed microzonation study of the key developed areas of Nias Island, particularly low-lying and coastal areas. 5. Build capacity within BRR to facilitate the process of spatial planning on Nias Island, in relation to seismic and tsunami hazards. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 7 of 80 6. Recommend a framework for the revision and implementation of building codes according to seismic (and tsunami) hazard of Nias Island, also within the wider context of Aceh. 7. Recommend guidelines for reconstruction of buildings on Nias Island, in consideration of future hazards and community vulnerability. 8. Advice on education and public awareness programs to enhance understanding and build community resilience for future earthquake and tsunami. The Advisors activities were not, however, confined to the above as requests were made throughout the duration of the services by BRR for advice and assistance in other areas. 1.2 EARTHQUAKES AND TSUNAMIS OF 26 DECEMBER 2004 AND 28 MARCH 2005 Earthquakes have shaped both Nias Island and the culture of its inhabitants. Great earthquakes are a frequent occurrence on this tropical island, which sits on top of what tectonic geologists call an accretionary wedge of a subduction zone. The subduction zone is formed by the collision of two tectonic plates, which in the Nias region are moving towards each other at a rate of approximately 60mm per year. It is this movement that causes the earthquakes. The coastline of Nias has been regularly uplifted by the great subduction zone earthquakes, exposing coral reefs and causing new ones to grow. The mountains of Nias were also formerly folded and faulted by these same tectonic processes. A feature of the great earthquakes is that they generate tsunamis which sweep ashore, inundating the coastline with powerful waves. In response to these events the people of Nias lived on and in the hills where they built beautiful villages with wide, stone paved streets and steps, bordered by stone carvings and rows of remarkable traditional houses which incorporate advanced earthquake engineering concepts. The wooden houses with peaked thatch roofs have bracing systems supporting the roof and walls, as well as the foundations, which have high wooden piles sitting on stone blocks on the ground. The braced pile system which is not fixed to the ground, allows the structure to displace in response to seismic waves, forming a type of energy release mechanism for the house. Some of the braceding systems are weighted with rocks in order to be effective. Villages of such houses are an early version of what we now call “Community Based Disaster Risk Management”. These Nias communities have used their collective knowledge and wisdom to mitigate and live safely with the frightening and destructive effects of the earthquakes and tsunamis which have frequently impacted their tropical paradise Island. Their disaster risk management has allowed them to develop a vibrant and colourful society with a rich culture of dance, music, stone and wood carving, and other traditions. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 8 of 80 The Chiefs house in Bawomataluo Bracing and piles below the Chiefs house A traditional house in Gunung Sitoli with piles on stone blocks Bracing and weighting used for earthquake resistance Earthquakes and tsunamis normally inflict devastating losses on lives and infrastructure and housing assets requiring the need for lengthy and costly rehabilitation and reconstruction. Buildings and infrastructure built up over years of development can be wiped out in an instant. The tsunami which triggered the most immense and widespread destruction in modern history took place in the Indian Ocean following a MW 9.3 (Moment magnitude) earthquake near the island of Simeulue in the Province of Nanggroe Aceh Darussalam, on 26 December 2004. The tsunami devastated Banda Aceh City and the west coast of Aceh as well as causing significant damage on the island Nias in North Sumatra. The tsunami also wreaked havoc in the countries surrounding the rim of the Indian Ocean including Thailand, Malaysia, Andaman and Nicobar, Sri Lanka and the East coast of Africa. A death toll of 165,862 (including the 37,066 reported missing was reported in the Aceh and Nias. The total economic loss has been estimated at 41 trillion rupiah, exclusive of indirect losses caused by the interruption of economic activities. The effects of the 26 December 2004 were light on Nias compared with Aceh and other countries such Thailand and Sri Lanka. A total of 122 deaths, 18 missing, and 2,300 people directly affected were recorded. On 28 March 2005, only three months later, a massive earthquake recorded as MW 8.7 on the Richter scale struck the island of Nias. This earthquake was devastating for the mainly rural areas in Nias and caused the death of 839 people. About 6,300 were injured, 70,000 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 9 of 80 people made homeless; 13,000 houses destroyed and 60,000 houses damaged; 12 ports and piers damaged or destroyed; 400 bridges and 1,000 km of road impassable; 760 government buildings damaged, 720 schools destroyed, two hospitals damaged and 350 health clinics damaged, 1,940 religious buildings (churches and mosques) damaged, and 90% of people had their livelihoods disrupted. 1.3 DISASTER RISK REDUCTION The work undertaken by the Technical Advisors should be viewed as part of an overall effort by UNDP and the Government of Indonesia to contribute to disaster risk reduction (DRR) within a community with high risk of natural hazards in Indonesia. The UN Economic and Social Council’s Resolution Number 63/1999 calls for world governments to formulate and implement a National Action Plan for Disaster Risk Reduction to support and ensure the attainment of the objectives and targets of sustainable development. The Hyogo Framework for Action 2005-2015 urges all countries of the world to prepare an integrated disaster risk reduction mechanism that is supported by a proper institutional basis and adequate resources. With support from UNDP BAPPENAS, the Indonesian Government Planning Agency, has prepared a “National Action Plan for Disaster Risk Reduction”. This is being supported by Indonesian Government legislation. On 29 March 2007 the Dewan Perwakilan Rakyat (DPR) approved new legislation that will bring Indonesia into line with the Hyogo Framework for Action 2005-2015 and have wide reaching changes in the way Indonesia approaches disaster management. The formulation of the National Action Plan for Disaster Risk Reduction, which later on will be referred to as RAN-PRB, involves a nation-wide process that engages national and sub-national stakeholders from government, civil society and the private sector. The participatory approach was employed because RAN-PRB comprises an integrated plan that includes social, economic and environmental aspects. The Action Plan has also been adapted to fit in with regional and international disaster risk reduction plans. The community occupies a crucial position in the Action Plan, given that it is a subject, object and main target of disaster risk reduction efforts. The Action Plan must adopt and respect local wisdom and traditional knowledge prevailing in Indonesian communities. Both aspects are key in making disaster risk reduction a success considering the depth and variety of tradition growing in Indonesia. As subject, the community is expected to enhance access to all formal and informal information sources, hence allowing for direct involvement of the community in disaster risk reduction. The government is expected to make available accessibility facilities and infrastructure as well as adequate resources to implement the action plan. RAN-PRB also reflects a shift of paradigm in disaster management Indonesia. There are three important aspects to this paradigm shift: ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 10 of 80 1. Instead of focusing merely on emergency response, disaster management now represents all aspects of risk management 2. Protection against disaster threats must be provided for by the government not out of obligation but for the fulfilment of the basic human rights of the people 3. Responsibility for disaster management lies no longer with the government alone, but a shared responsibility of all elements of the society The 2006 National Plan recognises that the responsibility for disaster management lies no longer with the government alone, but is a shared responsibility with all elements of society. Community Based Disaster Risk Management (CBDRM), which is being adopted widely in South East Asia, takes this process to the community building blocks at the heart of society. It is a process of disaster risk management in which at risk communities are actively engaged in the identification, analysis, treatment, monitoring and evaluation of disaster risks in order to reduce their vulnerabilities and enhance their capacities. This means that the people are at the core of decision making and implementation of disaster risk management activities. The involvement of the most vulnerable is paramount and the support of the least vulnerable is necessary. In CBDRM, local and national governments are involved and supportive. In Nias the disasters to be mitigated are from Natural Hazards, which include earthquakes, tsunamis, flood, landslide, possibly strong wind and drought, and pandemic – such as bird flu. The risk of a disaster is a combination of the size or strength of the natural hazard and the vulnerability of the community: Risk = Hazard x Vulnerability Communities in Nias are vulnerable to natural hazards for a variety of reasons: because of limited access to resources, age and gender balance (many women, children and elderly), poverty, education, training and skills, population expansion, urbanisation, uncontrolled development, environmental degradation, living in dangerous locations, dangerous buildings and low income levels. Some natural hazards can be mitigated by good planning (such as exposure to tsunamis, floods, drought, landslides and pandemic) but others can not (such as the magnitude of an earthquake). The main thrust of DRR is to reduce vulnerability. Many of the vulnerability issues are being tackled directly and indirectly by programs within the Four Strategic Pillars of BRR. After disasters the size of the Aceh and Nias tsunamis and earthquakes, the first requirement was for short term emergency response on an unprecedentedly large scale, providing medical care, food, drink and shelter. This is very difficult when the basic infrastructure of roads, bridges, ports and airstrips are badly damaged and destroyed. Next comes rehabilitation, with the restoration of basic community services and functions, followed by a longer duration reconstruction phase taking years, with resumption of services – plus preventive measures. Mitigation in the form of risk assessment, prevention and preparedness, can be implemented when reconstruction is underway. Mitigation includes hazard mapping, hazard and community vulnerability assessment, building improvements, structural and non-structural measures. Preparedness includes contingency planning, warning and evacuation procedures and preparations for possible future natural hazards. Because of immediate and pressing needs, mitigation measures can not be realistically introduced in the initial relief and rehabilitation phases of a disaster. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 11 of 80 In Nias these mitigation measures are planned to be introduced into reconstruction efforts for 2007 and 2008 by a UNDP sponsored, integrated disaster risk reduction program. As large magnitude, subduction zone earthquakes, tsunamis and floods are relatively frequently occurring events for Nias, the Disaster Risk Reduction (DRR) project seeks to develop a community awareness of natural hazards and to build capacity for development planning that reduces vulnerability at the local community level. As well, it seeks to influence development of plans at Sub-District, District and Provincial levels to incorporate risk reduction planning into programs and budgets. It will develop the community response end of an early warning system. The project will aim to teach a culture of safety, beginning at primary school level, to develop a comprehensive and effective public awareness program tailored to local conditions, and to help local communities to develop risk reduction plans and to implement them. 1.4 BUILDING QUALITY It is often said “it’s not earthquakes that kill people, it’s buildings”. By far the most deaths that have occurred in Indonesia following earthquakes have been as a result of the collapse of buildings and houses. The most important aspect of in regard to the reduction in probable deaths through future earthquake events is to improve the design and construction of houses and other buildings. This is of particular importance on the island of Nias which is located in the highest seismic risk zone in Indonesia (Zone 6). It has been observed on Nias that many well meaning donor agencies have constructed houses, schools and clinics to their own standards, rather than standards that are legally required in Indonesia. BRR is now moving toward encouraging these agencies to construct buildings in accordance with Indonesian regulations. Local government agencies are responsible for the oversight and enforcement of Indonesian government regulations related to buildings. Over the past two years much reconstruction work has been undertaken with minimal involvement from local government. BRR recognizes this and is in the process of forming joint secretariats with Local Government and is providing assistance with capacity building to enable Local Government to meet its obligations under the Indonesian building code. Indonesia has well developed building standards for seismic loading, which if always used and the quality of construction enforced, will strongly mitigate against the risk of building collapse during earthquakes. 1.5 ROLE OF LOCAL GOVERNMENT Special initiatives are needed to review and strengthen such areas as building by-laws, land use zoning, and environmental management guidelines to ensure increased resilience against the natural hazards. Many of these initiatives flow from the application of Community Based Disaster Risk Management. Some examples of these are as follows: ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 12 of 80 1. Strengthening public awareness and preparedness of local government and local communities with the priority on disaster-prone areas. 2. Disseminating hazard zone mapping to the local levels with its integration into land-use planning. 3. Strengthening people’s capacity through training and education. 4. Strengthening capabilities in disaster detection by providing infrastructure and human resources 5. Establishing integrated rapid and accurate response mechanisms. 6. Issuing procedures and guidelines in disaster management. 7. Preparing legislation in disaster prevention, mitigation, and response. 8. Developing a disaster management information system. 9. Preparing legislation in disaster prevention, mitigation, and response. Longer-term disaster risk reduction must be incorporated into development planning. The strategic elements outlined above bridge the gap between reconstruction and development process and transcend the present institutional and legal framework of the regional coordinating agency for disaster management with following functions: 1. Expanded requirements for hazard and risk assessment with special attention for housing, infrastructure, and future community planning. 2. Review and necessary revision of design practices, implementation guidelines, and construction standards. 3. Training of replacement public administration officials. 4. Environmental and natural resource management with special regard to land use zoning, ecological conservation of mangroves as safeguards against coastal disasters. 5. Restoration of livelihoods and development of social welfare and protection measures. 6. Coordinated development of information and communications opportunities for public education. Following the example of Sleman Kabupaten in Yogyakarta province, an institutional regulation framework is planned for adoption by the two Kabupatens of Nias. In order to deal with emergencies caused by regular eruptions of Merapi volcano, Sleman has district regulations setting up an emergency management unit and its operations, including evacuations and emergency shelters, during a volcanic eruption. In consultation with local government, the BRR plans to adapt these regulations to be applicable for the natural hazards affecting Nias, such as earthquakes, tsunamis and floods. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 13 of 80 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 14 of 80 2. GEOLOGY OF NIAS ISLAND 2.1 PHYSIOLOGY Nias Island can be divided into two geomorphologic units (see Figure 2.1): 1. Low lying plains, 2. Rolling and steep hills. The low lying plains cover the outer part of the Island. They cover about 35% of the Nias land area and have a height between 0-50 metres above sea level gentle relief and slopes of 0-5%. Generally these low lying plains consist of normally consolidated alluvium deposited in river, swamp estuarine and coastal environments. The rolling and steep hills are mainly located in the interior part of the Island and cover 65% of the total area and are of elevation between 50-800 metres. Their form is undulating ridges with moderately to steeply dipping side slopes. This area consists of various types of rocks classified according to geological age into the Mélange Complex, and the Lelematua, Gomo, Gunungsitoli and Alluvium Formations. 2.2 STRATIGRAPHY The rock units of Nias Island, from the oldest to the youngest, are the Mélange Complex, Lelematua Formation, Gomo Formation, Gunungsitoli Formation, and Alluvium deposits. The description of each formation as follows: 2.2.1 Mélange Complex The Mélange Complex consists of various blocks of peridotite, serpentinized gabro, serpentinite, basalt, schist, shale, greywacke, conglomerate, breccias, limestone, sandstone, and chert; with a fissile groundmass. Many calcite and quartz veins are found. The complex shows a tectonic contact with the Lelematua Formation of Early to Late Miocene age. Based on its stratigraphic position, this complex is interpreted to have been formed during the Oligocene – Lower Early Miocene time. Its distribution covers the central part of Nias Island, from the northwest – southeast. 2.2.2 Lelematua Formation The Lelematua Formation consists of alternating sandstone, claystone, siltstone, conglomerate and tuff with thin intercalations of coal and shale. It is well bedded and strongly folded. Generally it has sedimentary structures, including parallel lamination, graded bedding, and convolute lamination. Based on the presence of planktonic foraminifera’s, the age of the formation is Early Miocene to Late Miocene and it is ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 15 of 80 deposited in a sublitoral to outer neritic environment. The upper part of this formation interfingers with the Gomo Formation and the lower part unconformably overlies the Mélange Complex. It has a thickness of 3,000 metres in the eastern part and 2,000 metres in the middle of Nias. The type locality of the formation is at Lelematua, close to Gomo village, in the southern part of Nias. Previously it was named the Nias Formation (Union Oil Company). Figure 2.1. A Topographic map of Nias Island. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 16 of 80 2.2.3 Gomo Formation The Gomo Formation consists of claystone, marl, sandstone, limestone intercalated by tuffaceous marl, tuff, and peat. Generally this formation is well bedded and strongly folded. Common sedimentary structure is parallel lamination. Based on a fossil assemblage of planktonic foraminifera, the age of this formation is Middle Miocene to Early Pliocene (N11 – N19), deposited in a sublitoral to bathyal environment. The unit also contains mollusks. The lower part of the formation interfingers with the Lelematua Formation and it’s unconformably overlain by the Gunungsitoli Formation. The thickness of the formation is about 1,250 – 2,500 metres. Type locality is in Gomo, located in the southern part of Nias Island. Other names for of this unit are the Upper Marl-Limestone Series (Elber, 1939 or Nawalo Formation (Moore, 1979). 2.2.4 Gunungsitoli Formation Gunungsitoli Formation. Gunungsitoli formation consists of reef limestone, silty limestone, calcareous limestone, calcareous fine grained quartz sandstone, marl, and sandy clay, well bedded, and weakly folded. This formation is of Plio-Pleistocene age (Bemmelen, 1949). It was deposited in a shallow marine environment, unconformably overlies the Gomo Formation and Lelematua Formation. Thickness is about 120 metres. Type locality of the unit is in Gunungsitoli (Burrow & Power in Situmorang, 1975). 2.2.5 Alluvium Alluvium consists of river, swamp, and coastal deposits which contain boulders of limestone, sand, mud, clay and peat. Thickness ranges from 2 to 10 metres. 2.3 GEOLOGY, STRUCTURE, TECTONICS AND GEOLOGICAL HAZARDS OF NIAS 2.3.1 Tectonics The tectonics of Sumatra are a result of the oblique collision of two crustal Plates, the Southeast Asian Plate (thicker, lighter, continental crust) and the Indo-Australian Plate (thin, denser oceanic crust) (Figure 2.1). When lighter continental crust collides with dense oceanic crust, the dense crust is subducted beneath the lighter crust. The collision velocity of the two plates is 52 – 60 mm/year (Figure 2.1) and as the subducted plate slowly descends under the continental crust margin, rocks and sediments are scraped off its surface to form the fore arc wedge and islands (Figure 2.2). In general, because of strong friction, the subduction surface between the two plates is locked and strain builds up for tens to hundreds of years until the surface suddenly slips and ruptures, releasing energy as a large earthquake. Nias is located at the margin of the plate boundary as an outer arc island. These islands are generated as an uplifted product of the crustal plate collision and subduction, illustrated in the diagrams of Figure 2.2. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 17 of 80 2.3.2 Structure Figure 2.2 shows two interpretative cross section models of the Sumatra fore arc from the Indian Ocean, through Nias, to the volcanic arc on the mainland of Sumatra. The figure shows (a) Karig (1979) and (b). Samuel (1999) models. In the Karig model, the sedimentary basins on Nias are considered to have developed as slope basins on their inner trench slope and to be over thrust on their northeastern sides by slices of accreted oceanic basement. In the Samuel model, the sedimentary basins on Nias are considered to have originated as half grabens due to extension of the fore arc, with thrusts occurring subsequently due to inversion of the bounding normal faults. Figure 2.2. Tectonic setting of Sumatra, showing the subduction of the Indo-Australian plate underneath of the Southeast Asian plate. The relative movement of the IndoAustralian plate is around 52 – 60 mm/year (After Danny H. Natawidjaja, 2002) ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 18 of 80 2.3.3 Geological hazards The geological hazards of Nias, caused by its tectonic environment and topography are: • • • • • Earthquakes Tsunamis Landslides and permanent ground movements related to earthquake shaking, such as consolidation subsidence and lateral spreading Tectonic uplift and subsidence Flooding The geology and structure of Nias Island, are shown in Figure 2.3. Structural features are folds, faults, and lineaments, with the structural pattern trending to the northwest southeast. Anticlines and synclines are symmetric with some plunging to the northwest and southeast. Thrust faults parallel the fold axis are dipping to northeast of about 30º - 40º and bounding the Mélange Complex with the younger sedimentary covering units. Thrust faults and folds are crossed by strike slip and normal faults. Lineaments found in tertiary rocks are trending to northwest – southeast. Tectonic activity commenced at Oligocene time as a thrusting process of the Mélange Complex. During Early Miocene – Pliocene, deposits of the Lelematua and Gomo Formations were deposited at the surroundings of the mélange high. The Plio – Pleistocene tectonics phase caused faulting and uplifting all of rock units. The tectonic activity seems to be continuing until now, as shown by the formation of Quaternary reef terraces of the Gunungsitoli Formation and of growing coral reefs. Figure 2.3 Interpretative cross-section of the Sumatra Forearc from the Indian Ocean through Nias to the volcanic arc on the mainland of Sumatra. (a) Karig model. (After Karig et al., 1979); (b) Samuel model. (After Samuel & Harbury, 1999). ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 19 of 80 2.4 FAULTING The faults and folds shown on the geological map (Figure 2.3) and on a more detailed Nias geological map (Djamal, Gunawan, Simanjuntak and Ratman, 1994) are regarded as geologically old features and are not currently active faults. As shown in Figure 2.2 models, the Nias Island surface faults are no longer directly connected to the main subduction fault surface and subduction fault movements cannot be directly transmitted to them. The present main active faults are considered to be the subduction zone interface located some 20 to 24 km beneath Nias, the great Sumatran Fault on the Sumatra mainland, the Investigator Fracture Zone to the south of Nias (Figure 2.1) and a boundary fault (the Mentawai Fault) between the fore arc islands and the continental crust. Although Nias was uplifted and tilted in the 28 March 2005 earthquake, the main faulting in such great earthquakes is on the subduction zone many kilometres below Nias and is unlikely to reach the surface. No surface faulting has been recorded from the 2005 earthquakes. The old faults of Nias may accommodate some small secondary movement adjustments (in the mm to cm range) resulting from the main tectonic uplift, but are not considered to be primary, earthquake generating faults. Figure 2.4. A geological (Lithological and structural) map of Nias Island shows the pattern of faulting and folding and trending southeast- northwest directions. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 20 of 80 2.5 COASTAL UPLIFT AND SUBSIDENCE Geological evidence shows that Nias has been regularly uplifted by past great earthquakes, the last time in the 1886 earthquake.The great 28 March 2005 earthquake caused Nias Island to tilt to the NE. The entire length of the west coast of the island is uplifted approximately 2m while the furthest SE of the island has down-warped a little due to tectonic subsidence, reportedly about 0.3m at the village of Tagaeuli. There was also consolidation settlement in this area of up to a metre (Richard Stone, Science Vol. 314, 20 October 2006). The maximum uplift observed by the Technical Advisors was about 4m to 6m to the NW of Lahewa, with uplift of approximately 1.5 to 2m at Toyolawa, Afulu, Sirombu, pantai Muali and about 0.5 to 1m at Sorake on the south coast, with no uplift apparent at Teluk Dalam. At the Gunung Sitoli museum and zoo, the uplift is apparently about 0.5m, measured from high tide levels in the turtle ponds, which are tidal. In uplifted areas coral reefs are now (well) above high tide level and beaches are up to 200m wider. The uplifted former beaches and coral reef are rapidly being vegetated and within tens of years it will be difficult to recognize that they were formerly tidal areas. It is likely that people will wish to occupy such areas. New beach ridges are forming along the new shore line and a succession of such ridges away from the shore indicates uplifts from previous great earthquakes (Figure 2.4). Uplifted coral reefs are found around the perimeter of Nias, indicating that in the last 100’s of thousands to a few millions of years, the great subduction zone earthquakes have gradually been raising Nias out of the sea. Uplift from the sea is generally benign or even benevolent and much easier to live with than subsidence, where the sea comes flooding into former land areas. With uplift, drainage is improved, potentially usable land area increases, but ports may become shallower. With subsidence the effectiveness of drainage decreases, rivers and adjacent land becomes more prone to flooding, swamps increase, the sea can invade formerly fertile areas and areas of land can become uninhabitable. However, for other reasons the great Nias earthquake has initially caused a severe adverse impact to the population of Nias by causing damage to infrastructure, buildings, and disrupting livelihoods and transport. Now with assistance pouring into Nias and rebuilding in full swing, the people of Nias have been given a chance to turn disaster into opportunity. A relatively isolated, poor and forgotten island is on the centre stage in the eyes of the world and could become a show-case for constructive and sustainable development, a place people will want to visit to see first-hand the dynamic and vibrant culture and relax in a warm, friendly environment. The Advisors recommend that the uplifted beaches and reefs of Nias are zoned as plantation reserve and remain unoccupied, as they are a high hazard area for tsunamis. The Advisors suggest that these areas are used productively as coconut tree plantations, along with cocoa or other suitable bushy plantation trees beneath the coconut trees. People will be tempted to move in and live in these areas and there could be commercial pressure in the future for some of the attractive beach areas to become resorts for tourism. This sort of activity where people congregate and live will require careful planning so that lives are not put at risk. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 21 of 80 The tectonic uplift and down-warping from the earthquake has been measured and recorded not long after the earthquake by a team from The Indonesian Institute of Sciences (LIPI) and the California Institute of Technology in Pasadena (CALTEC), (Richard Stone, Science Vol. 314, 20 October 2006). Figure 2.5. An aerial view of beach ridges uplifted by past great subduction zone earthquakes at Sirombu on the mid west coast of Nias. At least 6 beach ridges and possibly as many as 9 can be seen. The peninsula at the bottom of the photo is an atoll which has become joined to the main island of Nias, probably after the earthquake and uplift which occurred before the 1861 earthquake. Four of the ridges are arrowed If suitable organic material can be found in these beach ridges it can be carbon dated and a history of timing and uplift of the past 6 or 9 great Nias earthquakes could be established. It may also be possible to do similar work on other parts of Nias too where there are suitable sites – such as a progressively uplifted coral reef. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 22 of 80 This uplifted beach near Lahewa is rapidly becoming vegetated 2 years after the earthquake. The sea used to come to the location of the arrow and is now more than 100m distant. New beach about 200m wide at Toyolawa. The high tide used to go nearly to the main trees before the earthquake. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 23 of 80 A new gravel ridge forming on the coral reef at Toyolawa. The former gravel ridge is about 100m further back from this one. Uplifted coral reef, short wharf now high and dry and new beach ridge forming at Sirombu. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 24 of 80 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 25 of 80 3 SEISMIC HAZARD ASSESSMENT 3.1 INTRODUCTION Geological hazards, such as earthquakes, tsunamis, landslides and storms periodically affect the Nias region, causing loss of life and extensive damage to property and infrastructure. Besides their immediate shaking damage effects, earthquakes can trigger tsunamis and landslides. Nias is located in a region with high seismic activity, one of the highest in the world. The “western” coastal areas facing the India Ocean are particularly vulnerable to tsunamis from such great subduction zone earthquakes. Although the tsunami from the second earthquake of 28 March 2005 was bigger than that of 26 December 2004, the people of Nias were prepared by their earlier experience and knew to evacuate coastal areas to higher ground as quickly as possible. Although the Nias earthquake occurred at 11pm when people were in bed sleeping, all the people the Advisors talked to evacuated their coastal houses as soon as the shaking stopped and very few were killed by the tsunami. Some houses and losmen at Sorake were damaged by the tsunami, but ports and roads and bridges in Nias were mainly damaged by earthquake shaking rather than the tsunami. Earthquakes cannot be reliably predicted. We would all be better prepared for earthquakes if we knew when the next one was coming. However, unlike a storm front that must travel to you before torrential rain begins, there are no reliable warning signs for earthquakes and there is not yet any scientifically verifiable way to predict earthquakes. Even though we cannot predict the time of the next earthquake, science and engineering can help us mitigate against the destructive effects of earthquakes. The road to earthquake safety follows several steps. First, the magnitude of earthquakes can be estimated through geological considerations (Chapter 2). Given that earthquake, we then estimate the strength of shaking (Section 3.3 – The Design Earthquake for Nias). Given that shaking, we estimate the response of, or how strong to make different types of buildings and structures, such as bridges. With all these steps completed, we can take the steps as a society to enact building codes and retrofitting programs to make our community safer. The Nias Islands are prone to earthquakes and tsunamis because they are located in one of the most active tectonic areas in the world. In order to gain an appreciation of damage caused by the 28 March 2005 earthquake, we made field trips to the main centres located around the Island. Observations were made of damage and rehabilitation to bridges, houses/buildings, ports, and roads. Specific attention was also given to earthquake uplift of coastal areas, the affects of the tsunami and the occurrence of landslides in the hills of Nias. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 26 of 80 3.2 FIELD ASSESSMENTS 3.2.1 General The following general assessments are of the affects of the the 28 March 2005 earthquake and the two – 26 Dec 2004 and 28 March 2005 tsunamis, based on field observations made while visiting locations around Nias. 3.2.2 Gunung Sitoli Town Gunung Sitoli can be divided into two landform types; an alluvium plain and undulating ridges. The alluvium plain, covering the eastern part of the coastal area, has a 10 - 500m width, and 0 - 6m height. It is formed of normally consolidated alluvial, swamp, and coastal deposits. The undulating ridges form much of the area of Gunung Sitoli town, but the commercial centre of the town, which consisted of up to three level brick and concrete buildings, is located on the coastal plain, and that is where much of the building damage and many of the deaths from the great 28 March earthquake were. The undulating ridges have gentle to steep slopes ranging in elevation from 6 – 250m above sea level. The ridges are sedimentary (accretionary limestone coral reefs) rocks of the Gunung Sitoli and Gomo formations. The limestone base rocks are remarkably stable and we have seen no landslide problems in these rocks in Gunung Sitoli or elsewhere on Nias. The heavily damaged section of Gunung Sitoli around Jalan Sirau and “Pasar Gunung Sitoli,” is one of the lowest-lying parts of the town. It has a shallow groundwater table, and is transected by the Gunung Sitoli River channel. However, it is also where most of the commercial buildings of the town were located. These were of reinforced concrete and brick panel construction without specific earthquake design, probably of Building Types 1 (large front shop opening giving a “soft storey” affect, making them prone to earthquake damage), 2 and 3. Inspection of the buildings that survived the earthquake shows that these appear to be of good quality, with many and thick columns and beams and small brick panels. Judging from these buildings which survived the earthquake, some without damage, it is clear that poor or non-seismic building quality is the primary reason for the concentration of building collapse and damage in the heart of Gunung Sitoli. 3.2.3 Sirombu Sirombu is located on the coastal plain in the central western part of Nias Island. The coastal plain consists of uplifted beach ridges (Figure 2.5), river alluvium and swamps with elevation of 0 - 5m above sea level. The beach ridges can be used to explain the more recent uplift history of Nias and can be correlated with the history of great earthquakes. The uplifted beach ridges seen in Figure 2.5 indicate that the atoll peninsula was joined to Nias by uplift in the great earthquake which occurred before the 1861 event. Sirombu town was formerly located on the neck of the peninsula which now connects an uplifted coral atoll to the main Island of Nias. It was destroyed by large, possibly amplified waves of the tsunami of the 26 December 2004 earthquake, which swept through the town from both sides of the peninsula, destroying buildings and killing 6 people. Fortunately ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 27 of 80 most of the town inhabitants remembered their traditional knowledge and quickly evacuated when they saw the sea retreating before the tsunami arrived. This saved many people, but one wonders what might have happened and how many more people would have died if the tsunami had occurred at night, when people could not see the sea retreat? This emphasizes the need for a tsunami warning system for Nias – not for the local great earthquakes which people feel very strongly and where people have 5 to 10 minutes to evacuate after the shaking stops, but for distant earthquakes which may not be strongly felt on Nias and where the time before the tsunami arrives is more than half an hour. The small Sirombu Port was uplifted by 2m by the earthquake, making the small wharf unusable (Photo Ch. 2), but the main wharf was undamaged by the earthquake and tsunami. The wharf structure is, however, being broken and split from internal corrosion and rusting of the reinforcing bars within its’ concrete and it will collapse from this cause in a few years. Internal corrosion of the reinforcing steel in reinforced concrete wharves seems to be a common problem in Indonesia. This needs to be recognized so that the new wharves under construction are built with good sand and aggregated to make dense concrete which has adequate cover over the reinforcement. As well there are concrete additives that should be used to help prevent corrosion of the reinforcing steel. The tsunami from 2004 Aceh earthquake destroyed the commercial town centre of Sirombu and a new town and housing further inland was already under construction when the 28 March 2005 great Nias earthquake occurred. This earthquake uplifted the coastal plain region about 2m and also produced bigger tsunami. However, the old town was not occupied and people along the coast were forewarned to evacuate by the events 3 months earlier. 3.2.4 Lotu, Lahewa and Toyolawa Lahewa, the main town of northern Nias, is situated on a coastal plain area with elevation ranging from 0 - 3m above sea level. Toyolawa village is located on a peninsula in the extreme north-western part of Nias. Lahewa is largely built on beach and alluvium deposits uplifted by past great earthquakes, while Toyolawa village is located on an uplifted atoll, which is now connected to the “mainland” of Nias by successive uplifts of previous great earthquakes. Lotu district is situated to the south-east of Lahewa. This area is formed of undulating ridges with gentle to steep slops and elevation from 0 - 250m above sea level. The hills are mainly rocks from, Gunungsitoli, Gomo and Lelematua Formations. Many buildings in the commercial centre of Lahewa were destroyed by the 28 March 2005 great Nias earthquake. This includes schools and government buildings. A large church building on higher ground in Lahewa was almost undamaged and is clearly designed to be earthquake resistant. The main wharf at Lahewa port collapsed and was not designed to resist earthquake loads as there was no structural connection between the wharf deck and the piles. The port was uplifted about 2m by the Nias earthquake and also experienced a 1 to 2m high tsunami from both the Aceh and Nias earthquakes, with the Nias earthquake producing a larger tsunami wave. The new port wharves are being built beside the former port facilities. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 28 of 80 3.2.5 The Road Section along Idanoi-Gido-Idanogawo The road section along Idanoi-Gido-Idanogawo is on a low lying alluvial plain with elevation 0 - 5m above sea level. The plain consists of weak and soft river muds, swamp and coastal deposits. Most of the main bridges along this part of the main road were damaged by the Nias earthquake. Many of the bridges are constructed on the soft muds and the bridge abutments were not designed to resist lateral spreading ground movements caused by the earthquake shaking. These abutments have sunk and rotated due to the lateral spreading, but the bridges can still be used because the superstructures appear to have retained their strength. As well, many of the steel truss bridges have jumped off their abutment seatings during the earthquake because of inadequate fastenings to resist seismic loads. The superstructures of these bridges are very strong and the bridges are still in use, but at some stage will need repair. The long bridge of Idano Gawo is constructed on the firm gravels of the braided Idano Gawo river plain. This bridge also jumped off its abutment seating’s due to inadequate seismic restraints, but was twisted and rotated because an unpiled abutment slipped into a river channel which had undermined it (see below). The Idano Gowo River bridge after the earthquake. The twisted section of the bridge has now been replaced by a Bailley bridge. 3.2.6 Teluk Dalam-Bawomataluo-Sorake Teluk Dalam is the main town of Nias Selatan. It is located in Teluk Dalam Bay at the southern end of Nias Island mainly on the coastal plain made up of weak alluvial materials (muds and sands). The town is surrounded to the north by hills composed of rocks units from the Gunung Sitoli and Gomo formations and the Melange complex. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 29 of 80 Many buildings were damaged and destroyed in the central heart of Teluk Dalam, including schools and government buildings. Although this part of the town is on weak ground, as is the case in Gunung Sitoli and Lahewa, most of the damaged and destroyed buildings were not designed for strong earthquake shaking. In the hills where there are villages with many houses built to traditional earthquake resistant design, the earthquake impact was light, but several landslides were seen. At Sorake beach the coral reef is uplifted by 0.5 to 1 m and several building were destroyed by the tsunami. The tsunami from the 2004 Aceh earthquake was about 1m high while that from the Nias earthquake was about 2 to 3m high. 3.2.7 Tuhemberua Tuhemberua and Sawo are a small town and village on the coastal plain north-east of Nias. Sawo is located on the banks of the Sawo River where it flows into the sea. Although we did not inspect its seating bearings, the steel truss bridge over the Sawo River appears to be undamaged by the earthquake. Most buildings in this area appear to be single storey. Rebuilding of schools and clinics indicates these areas suffered damage and losses in the earthquake. The effect of the two tsunamis appears to have been small or negligible on this part of the east coast of Nias. 3.2.8 Moi and Lolowa’u The road from Moi - Lolowa’u - Amandraya passes through the central hills of Nias. The forested hill slopes are gentle to steeply dipping and have an elevation from 250 to 450 metres. The basement rocks are from the Melange Complex and the Gomo and Lelematua formations. The forest includes native trees, rubber and cocao tree plantations. Creeping and slumping landslides were observed, some of which had damaged the roads. It is apparent that road construction through this hilly topography is difficult. Extra care has to be taken with drainage to ensure that poor drainage does not promote slope instability along the roads. “Bio-engineering” or using trees and vegetation to help stabilize marginally stable areas could also be used to help prevent damage to roads and infrastructure in these steep, hilly parts of Nias. Many landslides are initiated and kept moving by groundwater. In these cases drainage is often a practical, cheap and effective method for stabilizing slopes. Often drainage and/or bio-engineering using vegetation and trees are very effective and practical ways of dealing with slope instability in difficult terrain. 3.2.9 Gomo The town of Gomo is located in a fertile river basin area within the south - central hills of Nias. The surrounding hills are gently to steeply sloping with an elevation from 100 up to 700 m. The basement rocks are from the Gomo and Lelematua formations, and the Melange Complex. The rivers appear to be an excellent and bountiful source of aggregates for both road and building construction in Gomo The road from Lahusa to Gomo is in very poor condition. It appears that this road has not been maintained for many years. A separate report has been prepared on possibilities for widening the difficult Gomo Gorge section of the road, about 1.5km from the main Gunung Sitoli to Teluk Dalam road. This is attached as Appendix B. Collapsed “concrete” ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 30 of 80 houses can be seen in places along the road. In Gomo the Netherlands Red Cross are building attractive and very well built timber houses which would be an excellent model for houses in other parts of Nias where concrete is difficult to access. 3.2.10 West Sumatra On 17 and 18 March 2007 Advisors Dick Beetham and Bill Sinclair made a reconnaisance visit to West Sumatra. A report of this visit is contained in the attached Appendix C. 3.3 THE DESIGN EARTHQUAKE FOR NIAS 3.3.1 Introduction A commonly used seismic design standard for Building Codes is that “normal” buildings should be safe and undamaged in an earthquake with a 10% probability of occurrence in 50 years – which is equivalent to an earthquake which occurs on average every 475 years (approximately a 1 in 500 year earthquake event). Important buildings and structures, such as hospitals and clinics, government buildings, schools and universities, public halls and electricity generating stations, to name a few, have higher design standards and may have to be safe in a larger 1 in 1,000 year earthquake – or even the maximum probable earthquake. Using historical earthquake records, sometimes going back many centuries, in combination with recorded seismicity - generally only available for the last 50 to 100 years when there have been seismic networks available which record all significant earthquakes that occur - a probabilistic assessment can be made of the size (magnitude) and recurrence interval of earthquakes. There are many small earthquakes occurring all the time, but as the earthquake magnitude gets larger, the frequency of their occurrence decreases. For example in the Nias region small earthquakes which can just be felt occur every few days, but the very large earthquakes like the 28 March 2005 event occurs only every 150 years or so. Figure 3.1. The seismicity of Indonesia showing earthquakes of about Magnitude 5 and bigger which have occurred over a 5 year interval ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 31 of 80 As can be seen from Figure 3.1, the parts of Indonesia with the lowest seismicity are eastern Sumatra and Java and Kalimantan. With reference to figure 3.2 we shall go through the steps required for a seismic hazard assessment on Nias. 3.3.2 DERIVATION OF MAXIMUM PROBABLE EARTHQUAKE Step 1. The main and largest earthquakes affecting Nias are the great subduction events which have occurred on 28 March 2005 (MW 8.7), in 1861 (~Magnitude 8.5) and regularly in the centuries before that (see Figure 2.5). These great earthquakes on the subduction zone are due to the relative plate motion of ~60mm per year and the locking of the subduction zone, which periodically breaks free causing the great earthquakes. From seismicity we know that the distance from Nias to the subduction zone fault is about 24 km and this is the same for the entire island Step 2. For step 2 we know that the great subduction zone earthquakes have occurred in 2005, 1861 and regularly before that. Based on this evidence and the constant plate movement rate which leads to the build-up and release of strain on the subduction interface, we make the assumption that these earthquakes occur every 100 to 200 years. The magnitude frequency plot (Step 2 Figure 3.2), therefore has a concentration of great earthquakes (>Magnitude 8) with a recurrence interval of about 150 years. Thus deterministically the design earthquake is found to be about a Magnitude 8.7 earthquake about every 150 years, or 3 such events in 475 years. Steps 3 & 4. For Nias Island the distance from the ground surface to the source of the earthquake (the subduction zone fault) is about 24 km (Figure 3.3) and is constant for the entire island. Therefore the strength of shaking, as far as can be determined, will be fairly constant. This can also be determined from building and environmental damage, personal descriptions from those who experienced the earthquake, and from calculations of intensity. From all these sources it is a fair approximation to say the shaking intensity over Nias Island will be Modified Mercalli Intensity (MM) 9 to 10 during the great subduction zone earthquakes. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 32 of 80 Figure 3.2. The 4 steps which need to be taken for a seismic hazard assessment Nias Sumatra The subduction zone earthquake rupture surface Figure 3.3. The island of Nias is located about 24 km above the subduction zone fault. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 33 of 80 MM Intensity is used because it is practical, more useful and has far more meaning on Nias than Peak Ground Acceleration (PGA) and other methods of describing the effects of earthquake shaking at a particular site. The detailed MMI descriptions and the intensity scale is given in Appendix A following. Another advantage of using the MM Intensity scale for Nias is that it includes 6 building and structure descriptions, from Type 1 to VI. For MM 9 to MM10 Intensity shaking it is a clear requirement for buildings and structures to be designed and constructed to highest seismic standards. In terms of Disaster Risk Reduction for Nias, the most beneficial results can be achieved by ensuring all buildings and structures reach the high seismic resistant stands required to ensure they are safe in the great earthquakes. Completing Step 4 of the earthquake hazard assessment, we determine the 1/150 year recurrence interval shaking to be MM 9 to 10. Because the Magnitude ~8.7 earthquake producing this shaking recurs every 150 years and is close to the largest earthquake that can occur on the Nias segment of the subduction zone, the 150 year recurrence shaking is about the same as the 1/500 shaking and the 1/1,000 year shaking, etc., and the Magnitude 8.7 earthquake itself, is close to the maximum probable earthquake. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 34 of 80 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 35 of 80 4 DISASTERS RESULTING FROM NATURAL HAZARDS 4.1 WHEN NATURAL HAZARDS BECOME DISASTERS In order to develop the appropriate systems and measures to mitigate the effects of natural hazards, it must first be studied how such hazards become disasters. In Section 1.3 of the preceding chapter there is discussion about how the vulnerability of an area to a natural hazard (or the probability of occurrence of the hazard) defines the possible risk of exposure to the natural hazard at that place. A natural hazard is considered to be a natural disaster only when it causes both loss of life and considerable damage to property. For example, if a very strong earthquake affects an area far from human occupation, it becomes a piece of statistical information for the seismologists. However, even a relatively modest earthquake, such as the one that struck near Yogyakarta in 2006, can cause a disaster of large proportions because the village houses of that region were very vulnerable to earthquake damage. These houses had almost no resistance to earthquake shaking and several hundred thousand collapsed on their occupants who were inside, because the earthquake struck very early in the morning. Houses constructed to earthquake standards required for that region were undamaged and their occupants safe. The Community Based Disaster Risk management strategy for the region now is, with Government support and financial assistance, to rebuild houses to an appropriate earthquake resistant standard. Natural hazards produced by the forces of the nature, over which human society has no control, are the main causes in the creation of natural disasters. By comparing the scale of hazards vis-à-vis their consequences in the region, it is found in most cases, that the relative magnitude of damage to lives and property by far outstrips that of the natural hazard itself. This pattern, prevalent throughout the region, suggests that besides the usual natural forces, there are extremely important human factors which amplify the level of destruction and thereby transform natural hazard events into disasters. The key elements in this are population growth, poverty, environmental degradation, and inadequate information. Though these elements are inextricably linked to each other and it is quite difficult to segregate their isolated effects, the following paragraphs describe how these amplify the effects of natural hazards and act as the causes of natural disasters in the region. Rapid population growth in the region is one of the main elements that increase vulnerability to natural hazards causing natural disasters. In the first place, the higher rate of population growth directly results in high population density and a higher level of physical infrastructure. High population densities almost inevitably result in high death tolls, and high property values unavoidably result in high losses if appropriate preventive measures are not undertaken beforehand. In some areas with a high population concentration, even in the case of early warning of a natural hazard, preventive service measures cannot reach everybody. Consequently, a large section of people are left to face the hazards with their own means, even in developed wealthy countries such as USA where a cyclone devastated the city of New Orleans. Places of higher concentrations of physical infrastructure without adequate safeguards are very vulnerable to damage and the situation can become even more complicated as it is not easy to quickly rehabilitate such facilities. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 36 of 80 Furthermore, there are very dire indirect consequences of relentless population growth which, in most cases, are the main determining factor for the scale of the disasters emanating from natural hazards, particularly in urban areas where the population is concentrated. Increasing population pressure in the countries of the region causes habitation of hazard-prone lands. This is a very serious issue particularly in some of the least developed and developing countries of the region where per capita land availability is below the world average, whereas population growth is far higher. The other effect of rapid population growth, which has a direct bearing on a natural disaster, is the random development and enlargement of urban areas. The most important underlying causes for such unprecedented urban growth in the region are a relatively higher rate of natural growth in the cities and outwards migration of population from rural areas owing to poverty levels there. The main feature of urban growth driven by these factors in the region is the increasing emergence of slums and squatter areas in the outlying areas. These are often the most vulnerable areas with high disaster risks. As the physical and institutional capabilities of most of the least developed governments of the region to respond effectively to the increasing pressure of urbanization are not at adequate levels, the nature of overall urban development follows largely a disorganized and uncontrolled manner. In most of this region there are no master plans for the development of their urban centers. The increasingly serious problem of poverty, especially in the least developed areas of the region has been, as in the case of other socioeconomic domains, another major contributing factor for increasing losses from natural hazards. Poverty is another of the major underlying causes for the inappropriate types and poor quality of building materials, substandard planning and building code regulations and, most importantly, weak enforcement of safety codes and provisions. Also, because of a lack of resources, in many places relief and rehabilitation work cannot be carried out effectively. Degradation of the environment may by itself constitute a natural disaster, as for instance in the case of drought, or excessive soil erosion, groundwater or soil pollution, flooding in de-forested areas, etc. Adverse effects on food production and health conditions may be the result, but phenomena such as deforestation with/without overgrazing e.g., could trigger landslides or debris flows in landslide-prone terrain that would otherwise have remained only a low-level hazard zone. The destruction of mangrove forests along tropical coastlines, often to make room for shrimp farms or port facilities, thus expose the coastal population to higher risk of tsunami impact, as mangrove thickets constitute the last natural line of defense against such tidal waves. In the case of geology-related disasters, the lack of adequate information of the underlying hazard is among the most crucial causative factors; regrettably, it is also among the most common. Although the zones of recurrent seismic activity (the source areas) are usually well known and documented, this does not mean that the areas of potential damage (the target areas) are also well known – as was the case in Nias before the 28 March 2005 earthquake. As local ground motion in response to any earthquake from elsewhere is related to local geological conditions (rock, soil, or overburden characteristics), maps describing these conditions and their effect on hazard levels in some cases are helpful in risk assessment, particularly for large cities, which in turn would help authorities anticipate ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 37 of 80 where most relief crews and supplies ought to be deployed as a preparedness measure. But possessing adequate information does not guarantee its use. The most important lesson learnt from both the 26 December 2004 earthquake in Aceh and the 28 March 2005 earthquake in Nias is that the knowledge to significantly improve structures to resist earthquake damage and thereby avoid most of the deaths and financial losses did in fact exist; what was lacking was a consistent willingness to marshal the resources necessary to put that knowledge to work on the scale required to prevent disaster. The same is true of the West Sumatra Earthquake of 6 March 2007, which occured in an area where there have been four large, destructive earthquakes in the last 100 years. The lessons of the Nias earthquake should now be applied to the Mentawai Islands and Padang as a great subduction zone earthquake on the Padang segment of the subduction zone is anticipated any time in the next few tens of years. In order to develop the appropriate systems and measures to mitigate the effects of natural hazards, it must first be studied how such hazards become disasters. Vulnerability of an area to a natural hazard or the probability of its occurrence defines the possible risk of exposure to a natural hazard at that place. A natural phenomenon is considered to be a natural disaster only when it causes both loss of life and considerable damage to property. For example, if some very strong earthquakes affect areas far from human centres, they just become a piece of statistical information for the seismologists. However, even a relatively mild earthquake, such as the one that struck Nias and its environs, can cause a disaster of extreme proportions. 4.2 NATURAL HAZARD DISASTER MITIGATION 4.2.1 General An aim of the BRR NAD Nias is to prevent the disasters occurring by mitigating their effects on life and property. Local governments also, as authorities in charge of disaster management, can help to avoid future disasters altogether by reducing vulnerability to a low level and thus reducing to a minimum the risk of a disaster. Many individuals and even whole societies have come to accept natural disasters as a fact of life. Forces of nature, however, can no longer be considered the main cause of a disaster. As mentioned above there is an interrelated human dimension as well, therefore, the required disaster mitigation measures must also include this aspect. The level of disaster preparedness is a major factor in mitigation of natural disasters. There is a need for dissemination of information on the measures to be taken before, during and after a disaster event. In particular, preparedness measures need to be practiced periodically. Environmental planning is also necessary to avoid or mitigate losses from disasters, by using such instruments as land-use planning and disaster management. Mitigation of the effects of natural disasters and protection against natural hazards requires both structural and non-structural measures. Depending upon the characteristics of the hazard faced, such as type, location, magnitude, frequency, a combination of the following interrelated aspects of hazard mitigation may be needed: • Application of geology in land-use planning ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 38 of 80 • • • • • • Geology-related hazard mapping and risk assessment Early warning and management of geology-related hazards Protection against geology-related hazards Health aspects of natural disaster reduction Strengthening institutional frameworks for disaster mitigation Other aspects of geology-related disaster mitigation 4.2.2 Application of Geology in Land-Use Planning The physical impacts of natural hazards can be reduced by preventing or modifying the occurrence of the hazard, such as in the case of flooding. This can be done very effectively in relatively small catchments by land-use planning and management, particularly in areas where structural measures would be too difficult or too expensive to implement, for natural disaster reduction. Proper long-term land-use planning, by incorporating all geology-related data available, would identify and allocate hazard-free areas for urban development and thus be an effective way of dealing with natural disasters, with high gains at relatively low costs. However, as many people have inherited less-than-ideal living conditions in often unsuitable locations, there is a certain moral obligation to take the short-term view as well. Large concentrations of people living in hazardous zones, if they cannot or will not be moved to safer areas, deserve to have at least a fighting chance of survival in the event of a natural disaster. Authorities in charge of disaster management should therefore have at their disposal reliable estimates of the type, severity, and location of the damage likely to occur. On the basis of these data, contingency plans can be drawn up, including efficient relief operations to save lives. Damage to property can be limited if, for example, appropriate building codes are enforced for specific hazard zones. 4.2.3 Geology-Related Hazard Mapping and Risk Assessment A comprehensive vulnerability analysis should be undertaken in all hazard-prone areas, taking into account past disaster events (from the historic as well as the geological record), the socio-economic conditions of the population living in the area, the infrastructure and structural measures to counter the hazards in question, etc. Risk assessment may then be undertaken for all geology-related hazards. The seismicity of the region needs to be better understood. Major earthquake disasters in the region should be fully investigated and documented. There is a need for the free exchange of data among areas in the region in standardized formats. Attempts should be made to utilize the available data more effectively. Mechanisms of earthquake-generated tsunamis in certain parts of Indonesia also need to be better understood. A methodology should be developed for assessing the significance of earthquake and tsunami risk. A hazard booklet, including a map, should be prepared by scientists in the country, free of jargon and in the local language, for each potential earthquake and tsunami source in a country. There is a need to incorporate geological data in both long and shortterm planning to avoid or reduce the impact of natural disasters. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 39 of 80 4.2.4 Early Warning and Management of Geology Related Hazards Greater emphasis should be placed on expanding observational and monitoring systems, especially in areas of the region where data is scarce. There is still a need to establish or upgrade observational equipment and networks to monitor hazards properly and to disseminate warnings quickly through an efficient warning system. Existing seismic data acquisition networks in a region vulnerable to earthquakes should be updated and improved. Certain areas in the region still lack seismic data acquisition systems. Research in earthquake prediction should continue. Space technologies such as remote sensing, satellite communication and global positioning systems have been widely used in monitoring the occurrence of different types of natural disasters and in evaluating the losses and the impact. Even if many natural disasters cannot be averted, their impact can be reduced through timely warning and by evacuation measures being taken. Space-borne techniques can play a significant role here. It is worth noting the extreme precision with which vertical shifts in ground elevation (ground swell) can now be detected by remote sensing techniques like synthetic aperture radar. For tsunamis, early warning networks in the country should be completed. 4.2.5 Protection Against Geology Related Hazards Protection against natural hazards requires both structural and non-structural measures. Critical facilities such as schools, medical and public health facilities, drinking water supplies and communication installations should be located safe in areas unlikely to be affected by such geology-related hazards as tsunamis and landslides. Disaster-proof structures, such as shelters, emergency food and drinking water storage tanks, can be built in high-risk areas but easy access to such structures must be ensured. Special attention should be given to preparedness (Disaster Risk Management) and to emergency management, including restoration of lifelines, in large urban areas. It is necessary to regularly review community preparedness (Disaster Risk Management), local regulations and disaster resistant designs in light of events and experience in other places. For example many countries in the world are reviewing their tsunami risk profile and preparedness in the light of the size of and damage caused by the Aceh tsunami on 26 December 2004. The experience on Nias from the 28 March 2005 earthquake will be invaluable in helping the people of the Mentawi Islands and the coast of West Sumatra (Padang) prepare for a similar earthquake and tsunami events which are likely to occur in the coming tens of years. 4.2.6 Health Aspects In Natural Hazard Risk Reduction The importance of health and emergency services is clear when the sudden impact of a natural hazard strikes a community. In the immediate post-impact period, several hours or even days may pass before outside help arrives. During this period, people turn to their families, friends, neighbors, and local services for immediate help. When community members have been trained in Disaster Risk Reduction, including simple first aid, they can effectively reduce the numbers of serious casualties and deaths by reducing their vulnerability and can tend to injured before outside help arrives. In the same way, it is essential that health facilities and services continue to function after a hazard strikes. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 40 of 80 Therefore, it is important that health facilities are well located and constructed to highest standards to be able to withstand the effects of natural hazards, and are equipped so that they can provide basic assistance following emergencies of all kinds. Again, geologyrelated hazard zonation maps of appropriate scale can provide a good basis for deciding (1) which places are relatively safe for the construction of emergency and public health facilities and (2) where are most vulnerable places are and thus where the casualties are likely to be. The disruption of water and sanitation services during disasters is another major concern of the health sector. In highly populated towns, such disruption increases the risk of communicable diseases. These hazards can be minimized if public health officials work closely with municipal workers to set up a response system which reduces the risk of water contamination, water, and insect-borne diseases, and safe disposal of solid waste, as part of routine preparedness planning. Just as early warning systems can alert people to the impending tropical storms or volcanic eruptions, health services need to have dependable detection and reporting systems, particularly for epidemics, or of potential disasters such as bird flu. A key tool for identifying populations who are at increased risk from disaster, “a vulnerability assessment” is as relevant for the health sector as for other services. The populations likely to be most severely affected are often the poorest groups. These groups usually have limited access to basic services of all types, including health facilities, and face the greatest risk of death and disease following a natural or other catastrophe, and require special consideration. 4.2.7 Strengthening Institutional Frameworks for Hazard Mitigation Perhaps the most important need at the national or region level is to strengthen or develop capacity to undertake national or region hazard mitigation strategies. After assessing and mapping natural hazards experienced in the past and analyzing possible future risks and their potential social and economic effects, the adequacy of the existing risk reduction measures can be evaluated. Before this can truly be claimed for natural hazards, national, provincial and regional capacity should be strengthened to enable devotion of a significant portion of their human and financial resources to the collection, interpretation and presentation of data on geohazards for the use of planners, disaster managers and other decision makers. Disaster vulnerability assessments should be incorporated in the national development process so that projects and future investments reduce rather than increase vulnerability. In order to overcome resource constraints and to be effective, an action plan for natural disaster reduction in a vulnerable region should be incorporated in the overall economic and social development plans. The development programmes can be monitored to ensure that hazard reduction components are applied, such as building up the infrastructure and increasing the region’s resilience to disaster in the long term. There is a general need to establish or strengthen the institutional frameworks for natural hazard preparedness and mitigation, not only at national but also at regional, district, and community levels. National policies on disaster reduction strategies need to be formulated and widely disseminated. Contingency plans need to be formulated at national and sub____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 41 of 80 national levels, identifying the authorities responsible for taking the preparedness and relief-management measures, the triggering mechanisms and procedures for inter-agency interaction. The obligations of the community and the responsibilities of the Government should be clearly defined through appropriate legislation or executive orders. National action plans should aim at generating technical capabilities, strengthening the observational and warning networks, and improving research and development activities on natural hazards. Community awareness and educational programmes on warning systems and other aspects of disaster preparedness also need to be developed and implemented. Committees comprising representatives of non government organisations (NGOs) and the public could be established at the local level to monitor and guide disaster preparedness and relief operations. 4.2.8 Other Aspects of Natural Hazard Mitigation Geological processes are often measured in eons, and accordingly, geology-related natural hazards often manifest themselves at very long time intervals. As a rule of thumb, the longer the interval (return period) the more severe the hazardous event tends to be. For geology-related hazard assessments, the geological evidence of events that took place many thousands of years ago must be taken into account, and combined with the historical (written) record of disasters. The results of such combined data sets can be seen on the probabilistic seismic hazard maps. 4.3 SUMMARY AND CONCLUSIONS Geology-related disasters are generally some of the most destructive natural disasters in terms of human lives lost and property damaged. Based on geological conditions, earthquakes, tsunamis, flood, and landslides can potentially occur in Nias and their affects can be great loss of life and extensive damage to property and infrastructure. Due to tectonic conditions, Nias is in an area of high seismic activity. Earthquakes are rather difficult to predict and when such prediction can be made there is usually little time to issue adequate warnings to the people. In many countries it is gradually being recognized that the initial and most vital response to disaster must be at the local level and that the community must be well informed about disaster-preparedness measures and be alert in the time of disaster. In order to promote community involvement in disaster prevention and preparedness, community awareness programmes and educational programmes on warning systems and other aspects of disaster preparedness should be developed and implemented, and committees that would include representatives of NGOs and the public should be established at the local level, to monitor and guide disaster relief operations. The strategy needs to take into account the weakened administrative capacity brought on by the disaster, while also taking advantage of the post-disaster window of opportunity to strengthen capacity for disaster risk management. Some of the steps discussed below feed into each other, and they will need to be considered in the planning and sequencing of activities. Secondly, disaster risk management touches upon every area of people’s lives, and needs to be linked to sectoral plans and regional development goals. Both for short____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 42 of 80 term rehabilitation and longer term reconstruction that will reduce vulnerability, there are important considerations for a post-disaster strategy’s prevention, mitigation, and risk management components: 1. The protection of assets and property implies appropriate land zoning and spatial planning coupled with construction codes for better protection against a number of hazards. Reinforcement of existing codes (construction and zoning), improved enforcement of them and incentives for their use need to be part of the strategy for reconstruction. In a very real sense, the disaster in Aceh and Nias make the point clear that a return to the pre-existing conditions is undesirable. In many places, the coastline has been severely altered and new land use planning and sitting is inevitable. This will have to be balanced with the needs and desires of communities regarding relocation or rebuilding in situ. For example, for tsunami risk, the designation and zoning of tsunami run up areas for open-space uses such as agriculture or parks and recreation is recommended as the first land use planning strategy to consider. However, where communities need to be near hazard areas for their livelihoods, siting and engineering solutions that avoid, slow, steer, or block tsunami inundation can greatly reduce impacts. 2. Disasters create the opportunity to reshape existing patterns of development to minimize future losses. On the other hand, they can also create enormous pressure to rebuild the community quickly and just as it was before the disaster. These rebuilding issues should be addressed through the land use planning process with the active participation of the affected communities. 3. In order to develop the appropriate systems and measures to mitigate the effects of natural hazards, it must first be studied how such hazards become disasters. Vulnerability of an area to a natural hazard or the probability of its occurrence defines the possible risk of exposure to a natural hazard at that place. A natural phenomenon is considered to be a natural disaster only when it causes both loss of life and considerable damage to property. 4. Geology-related hazards, as well as other hazards produced by the forces of nature, over which human society has very limited control, are the main causes in the creation of natural disasters. Besides the usual natural forces, there is an extremely important human factor which amplifies the level of destruction and thereby transforms events of natural hazards into disasters. 5. Both environmental planning and structural measures are necessary to avoid or mitigate losses caused by geology-related disasters, by using such instruments as land-use planning and disaster management. Mitigation of the effects of natural disasters and protection against natural hazards require both structural and non-structural measures. 6. Proper long-term land-use planning, by incorporating all geology-related data available, would identify and allocate hazard-free areas for rural and urban development and thus be by far the most effective way of dealing with seismic disasters, with high gains at relatively low costs. 7. Earthquakes and tsunamis are the greatest hazard for this region, given their short return periods. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 43 of 80 8. Ensuring the protection of lives is the first priority for disaster risk management. In this context, the establishment of a network of seismographs along the country’s territory, coupled with an appropriate automated, real time alert system is cost-effective, and could be easily linked to a regional one – as is being proposed for the Indian Ocean’s rim countries and would provide a lead advance time for rapid mobilization to safer ground if coupled with appropriate community participation, education and ownership. 9. Structural measures to reduce disaster impacts must be coupled with nonstructural measures. For example, related to the point above, a technical warning system must be complemented by public education campaigns for appropriate reaction to the warning, and effective evacuation and preparedness plans. 10. Risk assessment and mapping has not yet been undertaken by most of the local government of the region. There is a need for comprehensive vulnerability analysis for disaster-prone areas, incorporating past disaster events, the socio-economic conditions of the population living in the area, and inventories of major structures of public concern. Risk assessment and hazard mapping would delineate areas vulnerable to natural hazards and the frequency, intensity, impact, return period etc. of each hazard. 11. The availability of pertinent geological information such as geology-related hazard maps should enable planners and decision makers to make the right choices and locate new urban areas away from hazard zones. This is among the most cost-effective measures aimed at natural disaster reduction. By comparison, existing cities require far more expensive measures that may at best have only a mitigating effect. Even so, urban geological information will be essential in both cases. It follows, that national geological survey departments should be requested and funded to collect relevant information and present this to planners, disaster managers and other decision makers in central governments an/or local authorities on a regular basis and in a format that is readily understandable to non-geologists. 12. Understanding and identifying earthquake hazards and setting the stage for mitigating them is a continuous process that transcends the immediacy of public attention to disastrous events. Wide-ranging efforts, from studying the fundamentals of earthquake physics to developing applied products such as probabilistic seismic-hazards maps, all contribute to a comprehensive program committed to reducing earthquake losses. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 44 of 80 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 45 of 80 5 SEISMIC MICROZONING IN NIAS 5.1 INTRODUCTION The response of different geological units to strong and weak earthquakes is known as seismic microzoning. The response of the geological units with respect to liquefaction, landslides and amplified ground shaking can be assessed and shown on maps. As well as seismic microzoning, such maps can show tsunami hazard zones. Amplified ground shaking is a difficult subject. Weak soils can strongly amplify weak to moderated ground shaking, but can reduce the effects (de-amplify) strong ground motions when these are strong enough to cause the ground to deform internally outside its elastic range. There can also be amplified ground motions due to topography and other effects. Rather than attempting to introduce a complex topic which has not been used in more advanced and relevant parts of Indonesia and many other countries, we have attempted to make this topic useful and relevant to the Nias context. It is very clear that the tragic and catastrophic losses on Nias from the great 28 March earthquake were due mainly to buildings and other structures (bridges, wharves, etc.) not being designed and constructed to adequate earthquake resistant standards. Seismic microzoning cannot remedy this issue for Nias, where great earthquakes are a regular occurrence. Seismic microzoning is useful in large cities, such as Tokyo or Jakarta, where there are a huge variety of buildings of different heights and designs. It is also used in New Zealand for towns where the response of a range of weak and strong ground motions have to be considered. In Nias buildings are one to three levels and of relatively uniform concept. As well, the design earthquake is the maximum probable earthquake, a very unusual situation. In this case all buildings have to be designed and constructed to the highest possible earthquake standards to be able to resist the very strong ground motions expected, and seismic microzoning can have limited impact. For these reasons, seismic microzoning can only affect relatively minor refinements on Nias, and the urgent first priority must be given to achieving the very high earthquake resistant building standards which are required for the island, in one of the most active seismic areas in the world. 5.2 PROPOSED MICROZONING FOR NIAS. We propose a simple and useful seismic microzoning system for adoption on Nias which does not have an unrealistic level of sophistication which would make it almost impossible to adopt. The design earthquake for Nias is caused by rupture of the subduction zone below the island, similar to the MW8.7, 28 March 2005 earthquake, the ~M8.5 1861 earthquake and the other great earthquakes before these latest two. Such earthquakes occur every 100 to 200 years and thus have a greater than 10% probability of occurrence in 50 years (a one in 475 year recurrence event. There are likely to be ~3 great earthquakes in 475 years). The MW 8.7 earthquake is likely to be close to the maximum earthquake that can occur on ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 46 of 80 the Nias segment of the subduction zone. It is uncommon for the probable maximum earthquake to be also the design earthquake for such short recurrence intervals. From listening to descriptions of people who experienced the 2005 Nias earthquake, from the damage it caused and from our calculations, we know that these great subduction zone earthquakes produce a shaking intensity of Modified Mercalli (MM) 9 to 10 (see Appendix A for these descriptions) for the whole of Nias Island. We use MM Intensity because it is practical, more useful and has far more meaning on Nias than Peak Ground Acceleration and other methods of describing the effects of earthquake shaking at a particular site. Although the epicentre of the 2005 Nias earthquake is shown as being located some 100 km to the north of Nias near Simeuleu Island, the epicentre of the earthquake is not where the earthquake energy was released, rather the energy release is on the subduction zone fault surface beneath Nias. Therefore it is not the distance from the epicentre that determines the strength of shaking for Nias, it is the distance to the fault plane, or the subduction zone rupture surface where the energy of the earthquake is released, which determines the strength of shaking. For Nias the distance to the subduction zone is about 24km under the entire island. In practical terms this is obviously the case because the full length of western Nias has been uplifted by ~2m and the entire island has been tilted. This could not possibly happen if the earthquake was represented by an epicenter 100km to the north of the island. As there is such a high intensity of MM 9 to 10 over the entire island, in practical terms the shaking can not get much stronger, and amplification and other such effects become rather academic. Clearly and most importantly, to be safe from earthquakes, buildings have to achieve the highest possible seismic resistant standards. This is what the traditional society of Nias knew and used for the construction of their traditional buildings, such as at Bawomataluo. It also appears to be the case that the traditional villages of Nias were built on elevated sites with firm or hard ground, and not in swampy areas where the ground low lying and soft. Our proposed microzoning for Nias proposes two classes of ground: 1. Firm or compact ground and rock; 2. Weak or soft ground which may liquefy and/or suffer gross ground movements such as consolidation settlements and lateral spreading during earthquakes. For both classes of ground, the design earthquake intensity is MM 9 to 10 and all building must be constructed to be safe at this level of ground shaking. Our observations in Gunung Sitoli and Teluk Dalam suggest that buildings constructed to withstand MM 9 to 10 intensity shaking will withstand another great subduction zone earthquake, similar to that of 28 march 2005, without significant structural damage. Thus according to the MMI descriptions in Appendix A, all buildings should achieve at least the standard required for Structures of Type V, and preferably should be constructed to achieve the standard required for Structures Type VI. Structures Type V. Buildings and bridges designed and built to resist earthquakes to normal use standards, ie. No special damage limiting measures taken, other than code requirements, dating from ~1970 for concrete and ~1980 for other materials. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 47 of 80 Structures Type VI. Structures dating from ~1980 with well defined foundation behaviour, which have been especially designed for minimal damage, eg. Seismically isolated emergency facilities, some structures with dangerous or high value contents, or new generation, low damage structures. Certainly any building which are required to be (fully) funcional after a great earthquake, such as hospitals, clinics, schools and government buildings (evacuation centres) should be built to Structure Type VI standards. The Advisors have chosen the two classes of ground above for the following reasons: • • For firm, stiff and hard ground the foundations required to adequately support buildings under high earthquake shaking loads are easier to design. For soft and weak ground there can often be gross ground movements due to differential settlement, liquefaction and lateral spreading. These ground movements can cause distortions to the building structure which in turn can cause it it be damaged and/or collapse – rather than the earthquake shaking alone. Thus the foudations for buildings in soft and weak ground need to be particularly well designed and should preferrably be specifically designed for a particular site based on a subsurface site investigation. However, for smaller buildings up to three levels in height, it should be possible to develop a minimum standard foundation design approach for use in areas zoned ‘soft or weak” ground. A Japanese team who were in Nias in January 2006 have outlined a potential liquefaction zone for Gunung Sitoli. Similar maps should be made for Teluk Dalam, Lahewa and other significant urban centres on Nias. An approximate soft or liquefiable ground microzoning map for Gunung Sitoli is shown in the following Figure 5.1. The land between the coast and the red lines is zoned “soft ground”. This microzonation study should be coordinated closely with relevant institutions, like Dinas Kimpraswil and Bapeda at local government level. Lessons from the study will aid the capacity building of the local government, especially in the processes and procedures for the establishment building code regulations. The microzonation study proposal should also envisage the development of systems for a city specific audit of construction practices as well as legislation for retrofitting and certification of existing buildings within a realistic timeframe. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 48 of 80 Approx. Zone of soft & weak ground Figure 5.1 Approximate soft or liquefiable ground microzoning map for Gunung Sitoli Lessons learned from the impact of the infrastructures damage level caused by the 28 March 2005 earthquake and to consider the priority scale of the reconstruction development of Nias, the microzonation study of Gunung Sitoli region might be better take into the last priority with some reason as follows: 1. At the present time, microzonation mapping in Gunung Sitoli and other urban areas on Nias is not a main priority, because most of the buildings in Nias (or Gunung Sitoli) are built less then four levels high. Seismic hazard maps will become important and useful only if PEMDA allows high rise buildings to be constructed. It seems unlikely that this will be permitted for some time to come. 2. Based on the physical rocks properties, 3. Within the Gunung Sitoli urban area there are two types of rock with differing physical characteristics. The first is hard and massive rock and is spread out in the undulating ridge region. The second is soft loose material which was spread out in alluvium and in the coastal plain region. The different physical properties of the rocks in this area needs to be considered in the design of buildings. 4. Site investigations should be carried out for all buildings greater than single storey constructed within the Gunung Sitoli urban area. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 49 of 80 5. Mapping of potential areas that may be susceptible to landslides arising from earthquakes. Such mapping is useful as an input into land use planning. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 50 of 80 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 51 of 80 6 CONSTRUCTION QUALITY 6.1 TRADITIONAL HOUSE CONSTRUCTION This fact was well understood by the traditional society of Nias who built structures (houses and other buildings) to a very advanced earthquake engineering standard, using bracing and props, and a foundation that is not fixed to the ground, so that it can step in response to the seismic waves of very strong ground shaking. Outstanding examples of this are the chiefs house at Bawomataluwo and the house near RRI in Gunung Sitoli (see Photos below). Interestingly these houses and villages also represent a Community Based Disaster Risk Reduction Strategy. The community made the decision to build their houses this way to be safe from the regular earthquakes and possibly also to be safer from raids by their adversaries, both potential disasters. Photo of the Chiefs house at Bawomataluo. This large house is said to be over 150 years old and in that case has withstood two great earthquakes in 1861 and again in 2005, without any damage. No nails were used in its construction ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 52 of 80 . The angle bracing and props used under the Chiefs house above. The traditional Nias house near RRI in Gunung Sitoli. The wooden plies are sitting on the stone blocks on the ground. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 53 of 80 Detail of the stone weighting system used to hold down the above house. Both the Bawomataluo and this house represent very advanced earthquake engineering practice. 6.2 BUILDING QUALITY PRIOR TO THE EARTHQUAKES OF 26 DECEMBER 2004 AND 28 MARCH 2005 During his first assignment to Nias (11 Dec ‘05 to 27 March ‘06), Dick Beetham made damage and reconstruction visits around Gunung Sitoli and to most of the main centres of Nias. Damaged and new buildings were photographed and digital files of all photos are available. The sections below are a collection of photographs used as illustrations, with comments added. Typically the collapse of masonry houses is caused by one or more of the following reasons: • • • • • • • • • Insufficient lap lengths in column reinforcing steel Bond failure where plain reinforcing steel has been used Inadequate confinement of masonry panels – e.g. no bond beams above and below windows; or above doors Inadequate or non-existent perimeter bond beams around the top of walls Column spacings too great Poor connections between beams and columns Inadequate stirrups (ties) around column reinforcing steel, particularly in joint regions leading to non-ductile failure Inadequate connections between ring beams at the top of wall panels with roof trusses Poor quality concrete ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 54 of 80 In Indonesian earthquakes the failure of engineered buildings has often been because the building structures were non-ductile reinforced concrete frames with unreinforced masonry infills, such solid bricks or thin concrete blocks. The connections between the infill panels and the columns and beams are typically poor or non-existent. Many houses and buildings survived the great earthquake of 28 March 2005 without significant damage. Many of those that collapsed had already been cleared away, so it was not possible to learn anything from them. However, there were some that remained and could be investigated. Structural failure due to light reinforcing and wide spaced (lack of) stirrups – a common problem Lack of sirrups in these round columns. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 55 of 80 Between December 2005 and 2007, Gunung Sitoli has transformed from a disaster area with many people in tents, to a “boom town” with a significant amount of new construction taking place. In general the new commercial buildings are being built well and will be seismic resistant. Judging from the buildings that survived the earthquake without significant damage, these new buildings will survive a similar event. The features required to ensure reinforced concrete and brick houses and buildings survival in great earthquakes are: • A good foundation with well reinforced ring beams and cross beams. In soft and weak ground areas (Microzone 2 areas) the ring beams and cross beams should not be more than about 4m apart, ie. giving floor panels not more than 4m x 4m. For buildings of more than one level, wider and deeper beams must be used. In all cases a reinforced concrete floor slab would add considerable strength in soft and weak ground areas; Well reinforced, closely spaced columns with sound concrete. In general the 100mm thick brick panel infill walls should not be more than about 3m square without using supplementary columns and beams. Stirrups (also known as ties) should be be of adequate size and not too far apart (typically about 100mm), particularly at joint regions where spacings may be less Well reinforced ring beams are required at the top of all masonry walls. All door frames and wall joints should be trimmed with reinforced concrete columns All windows should have reinforced concrete beams above and below the windows Roof trusses and beams must be well fastened to the tops of walls. Trusses should be used at the top of each column and the truss must be well connected into the structure (reinforcing rods) of the column. This is important for houses, as the corrugated iron roof is a strong diaphragm which adds strength at the top of the walls. • • • • • ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 56 of 80 The above building in Gunung Sitoli has a deep ring-beam at the top of the wall, numerous stirrups and reinforcing rods, beams and columns with wide dimensions, and intermediate beams in the brick panel walls. A steel framed concrete encased structure under construction in Gunung Sitoli. A good quality building in Gunung Sitoli with intermediate beams in the brick panel walls ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 57 of 80 Good ground beam and column reinforcing with well spaced stirrups 6.3 ROADS AND BRIDGES Earthquake damage to roads was caused mainly by differential settlement of the road in soft ground areas, landsliding, generally as slow moving landslides and slumps in the steep hills. However, in many places the roads were in very poor condition before the earthquake. Lack of road maintenance A very common problem on many of the roads in Indonesia, except in West Sumatra where the roads are better constructed and maintained, is poor drainage leading pot-holes. It is very important that road shoulders and side drains are regularly maintained so that water does not pond on the side of the road, leading to weakening of the ground and breaking up of the road. Regular maintenance is far cheaper than road reconstruction. Much funding could be saved by carrying out regular maintenance, such as making sure drains work and water is not ponding on or beside the road, and filling in potholes as soon as they form. Often roads are constructed with masonry side drains, but the walls of the side drain are too high for the water from the road to flow into them. This also causes a lot of road damage due to water ponding on the road shoulders and water running down the edge of the road rather than in the side drain. Many bridges also need maintenance such as cleaning and plastering where reinforcing steel has become exposed and is rusting. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 58 of 80 Earthquake damage to newer bridges was not to the superstructure. These appear to be well built and have performed well. The main problems are: • • abutment failures, such as settlement and rotation of the abutments due to lateral spreading of soft and weak ground. This is caused by insufficient strength and depth of piles. Poor fastening of the bridge superstructure to the abutment seatings. In many cases just a few small bolts have been expected to hold the bridge in place un the huge earthquake loads that are a regular occurrence in Nias It is sad to see easily avoidable earthquake damage. It is poor use of resources to have to demolish and rebuild a bridge which still has a sound superstructure when a little care and small extra cost originally would have prevented the earthquake damage. This earth abutment approach was lost by settlement and lateral spreading in the earthquake ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 59 of 80 This abutment pier sank and rotated due to lateral spreading indicating insufficient and lack of depth of piling. Both photos of the Muzoi River on the road to Lahewa. Another view of the rotated pier. The small square piles can be seen and are not strongly connected to the pier above. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 60 of 80 A bridge which has jumped off its abutment seatings and has dropped 2m A seating (arrow) has a small bolt in each corner – insufficient for earthquake lateral loads ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 61 of 80 A similar bridge in another location which has jumped off its seating and moved laterally A concrete bridge which has exposed reinforcing steel in its beams. This needs maintenance to prevent long-term deterioration. Detail shown below. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 62 of 80 Rotated abutment of another bridge. There appear to be no piles under the rear of the abutment and the connections of the top of the piles to the abutment are very weak. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 63 of 80 Detail of the above abutment - pile connection Road margin walls are often too high and prevent water draining off the road shoulder ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 64 of 80 Puddle formed at the edge of the road indicates lack of maintenance and will cause the road to break up ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 65 of 80 Water unable to enter the drain across the road shoulder often flows down the edge of the seal causing long-term problems ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 66 of 80 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 67 of 80 7 BUILDING CODE FRAMEWORK 7.1 INTRODUCTION As part of the overall goal of disaster risk management the Earthquake Advisors have undertaken a review of legal framework and building standards that exist in Indonesia and more particularly on the island of Nias. The objective of this portion of the work is to mitigate risks of buildings collapsing through natural hazards. The approach taken was to review existing codes and standards and to formulate recommendations that will be effective in mitigating the risk of building collapse in the long term. 7.2 INDONESIAN BUILDING LEGISLATION In Indonesia there is a three level approach by the Government aimed at controlling building standards, as follows: • • • Central Government Legislation Ministerial Decisions issued by the Department of Public Works (Previously known as KIMPRASWIL) Local Government (Pemerintah Daerah) hereinafter referred to as PEMDA Indonesian Government legislation relating to buildings is contained in “Peraturan Pemerintah Republik Indonesia Nomor 36 Tahun 2005 Tentang Peraturan Pelaksanaan Undang-Undang Nomor 28 Tahun 2002 Tentang Bangunan Gedung”. Hereinafter this document will be referred to as the Indonesian Building Code. This legislation provides more detail than the previous “Undang-Undang Republik Indonesia Nomor 28 Tahun 2002 Tentang Bangunan Gedung”. The objective of the Indonesian Building Code is stated as follows (Pasal 3): • • To provide for the development of functional buildings compatible and in harmony with the environment (Mewujudkan bangunan gedung yang fungsional dan sesuai dengan tata bangunan gedung yang serasi dan selaras dengan lingkungannya) To realize the organization of buildings in compliance with building technical standards including safety, health, comfort and ease or facility (Mewujudkan tertib penyelenggaraan bangunan gedung yang menjamin keandalan teknis bangunan gedung dari segi keselamatan, kesehatan, kenyamanan, dan kemudahan) To provide a solid legal framework for the development of buildings (Mewujudkan kepastian hukum dalam penyelenggaraan bangunan gedung) • The Indonesian Building Code applies to the following types of structures: ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 68 of 80 Housing, places of worship, business premises, social and cultural and special purpose buildings such as nuclear reactors, and defence installations. These categories are further broken down as follows (Pasal 3, 4, 5 & 6): • • • • Housing – includes permanent housing, terrace housing, apartments and temporary housing Places of worship – includes mosques, churches, Hindu temples, Buddhist temples and Chinese pagodas Business premises – includes offices, trade premises, industrial buildings, hotels, tourist and recreation premises, terminals and storage buildings Social and cultural premises – includes educational buildings, cultural buildings, health facilities, laboratories and general service facilities Under the Indonesian Building Code PEMDA is responsible for: • • • • • • Spatial allocation as per the local Regional or Town Planning Regulations (Tata Ruang Wilayah Kabupaten/Kota)(Pasal 6) Establishing the building function and issuing a Building Permit with the function stated (Izin Medirikan Bangunan (IMB))(Pasal 6) Agreeing any changes to building function (Pasal 7) Maintaining a building database (Pasal 13) Validation of the design of buildings by a team expert in Building Construction (Pasal 64) Capacity Building (Pembinaan) (Pasal 105 - 112) Building technical requirements cover the following: • • • Building spatial location and intensity (peruntukan dan intensitas)(Pasal 18) Building architecture (arsitektur bangunan gedung)(Pasal 22 – 25) Environmental control (pengendalian dampak lingkungan)(Pasal 26) Each PEMDA is responsible for developing local regulations pertaining to the above with the general requirements established by central government regulations. As well as administrative requirements this Code sets out the technical requirements of buildings in terms of safety, health, comfort and ease or facility (“keselamatan, kesehatan, kenyamanan, dan kemudahan (Pasal 3)). Each of these requirements is dealt with in detail and the requirements are summarized as follows: Safety (Keselamatan) (Pasal 17 – 20) Safety considerations are to include: • • • Design loadings – building to be of sufficient strength and to remain stable Fire resistance – passive and active protection Lightning - protection required Design loading is to include dead, live and loading form environmental events (wind and earthquake) ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 69 of 80 Building design is required to enable the safe egress of people in the event of building collapse Loading requirements are defined in standards issued by Ministry of Public Works. Health (Kesehatan) (Pasal 21 – 25) Health considerations related to building design must include the following: • • • • Atmosphere, climate (Penhawaan) Lighting (Pencahayaan) Sanitation (Sanitasi) Building Materials (Bahan bangunan gedung) Health requirements are further defined in standards issued by Ministry of Public Works. Building Comfort (Kenyamanan) (Pasal 26) Included under this category are requirements relating to: • • • • • Spatial relationship between rooms Air quality View (privacy) Vibration Noise Health requirements are further defined in standards issued by Ministry of Public Works. Ease or Facility (Kemudahan)(Pasal 27) • • Ingress and egress – safe for all users including babies, old age and handicapped people Infrastructure including parking, solid waste collection, communications, toilets, etc These requirements are further defined in standards issued by Ministry of Public Works. Building Organization (Penyelenggaraan Bangunan Gedung) (Pasal 34) The Building Code then covers aspects of Building Organization, including the following: • • • • Building Construction Building Use Building Maintenance Building Demolition Building construction (Pembangunan) (Pasal 35) The Building Code refers to the process of building construction as planning (perencanaan) and execution (pelaksanaan) together with supervision (pengawasaan) (Pasal 36). ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 70 of 80 In order to provide validation (pengesahaan) of compliance with central and local government regulations each PEMDA is responsible for technical evaluation of public building designs through the use of an “expert building construction team” (tim ahli bangunan gedung). For non-public buildings PEMDA has a responsibility to agree building designs but is not required to use an “expert building construction team”. Capacity Building (Pembinaan) (Pasal 43) Both the Central and Local governments are tasked with the development and education of parties involved in the design, construction and ownership of buildings. 7.3 INDONESIAN BUILDING STANDARDS Indonesian government building legislation provides the legal framework as described above and is supported by a range of Ministerial Decrees (KEPRESS) issued by the Department of Public Works, such as: • KEPMEN Nomor: 441/KPTS/1998 Tentang Persyaratan Teknis Bangunan Gedung (Technical Requirements for Building Construction) – this standard provides technical guidelines for building Construction, but precedes the Building Codes issued in 2002 and 2005 and is therefore in need of updating KEPMEN Nomor: 332/KPTS/M/2002 Pedoman Teknis Pembangunan Gedung Negara (Technical Guidelines for the Construction of Public Buildings) KEPMEN Nomor: 468/KPTS/1998 Persyaratan Teknis Aksesibilitas Pada Bangunan Umum Dan Lingkungan (Access Requirements for Buildings and the Surrounding Environment) KEPMEN PU Nomor: 10/KPTS/2000 Persyaratan Tentang Teknis Bahaya Kebakaran Pada banguna Gedung dan Lingkungan • • • In addition the Indonesian Standards Association issues standards related to Building Construction, such as: • • SNI 03-1726-2002 “Tata cara perencanaan ketahanan gempa untuk bangunan gedung” (Indonesian Earthquake Design Standard) SNI T – 15-1991-03 (Indonesian Concrete Design Standard) These standards provide more detail in each of the aspects of building design that are outlined in the Indonesian Building Code. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 71 of 80 7.4 NIAS BUILDING REGULATIONS The current Kabupaten Regulation related to Building permits is entitled Peraturan Daerah Kabupaten Nias Tingkat II Nias Nomor 16 Tahun 1998 (Refer to Appendix D). This regulation is supported by Keputusan Bupati Nias Nomor: 188.342/1530/K/2003 Tentang Petunjuk Teknis Pelaksanaan Tata Cara Pemungutan Retribusi Izin Mendirikan Bangunan” which includes a flow chart which describes the process to be followed. (Building permits in Indonesia are known as “Izin Mendirikan bangunan” which is abbreviated to IMB). Applications are required to go first to the Camat. The Camat is then required to verify the site location and post a notice at his office for a period of 2 weeks to allow objections to be voiced. The whole process is required by regulation to be completed within 30 days. The regulations and supporting Decision of the Bupati were issued before the Indonesian Building Codes of 2002 and 2005; and also before the destructive earthquakes of 26 December 2004 and 28 March 2005. These regulations need to be updated to reflect changes in the National Building Code together with the improved understanding of seismic risk of Nias following the earthquake of 28 March 2005. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 72 of 80 ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 73 of 80 8 CONCLUSIONS AND RECOMMENDATIONS Following is a summary of recommendations made by the Advisors: 8.1 DESIGN EARTHQUAKE This study has confirmed the 1/150 year recurrence interval shaking to be MM 9 to 10. Because the Magnitude ~8.7 earthquake producing this shaking recurs every 150 years and is close to the largest earthquake that can occur on the Nias segment of the subduction zone, the 150 year recurrence shaking is about the same as the 1/500 shaking and the 1/1,000 year shaking, etc., and the Magnitude 8.7 earthquake itself, is close to the maximum probable earthquake. The Indonesian Earthquake Design Code assigns Nias to the most severe earthquake zone 6. This study has confirmed that this is appropriate. 8.2 SPATIAL PLANNING According to people the Advisors talked to in Lahewa, Sirombu and Sorake, the tsunami wave from the Nias earthquake was bigger, about twice as high, as the earlier Aceh earthquake tsunami. Judging from these two tsunamis experienced in 2004 and 2005, the maximum and wave height was about 3m above sea level. Taking the Aceh and Nias tsunamis as being “typical” events, the Advisors recommend, as a preliminary measure until more data and comprehensive analysis is carried out, making a tsunami high hazard zone from sea level to the 5m contour level all around the coast of Nias. On the western, northern and southern coasts of Nias, the area between the 5m and 10m contours should become a medium to low tsunami hazard zone. We recomend this as a precautionary measure, in case larger tsunami than those reaching the 5m contour can occur. At this stage there is little knowledge about the capability of the Nias segment of the subduction zone to generate earthquakes greater than MW 8.7 and possibly greater tsunami than on 28 March 2005. The Advisors recommend that the uplifted beaches and reefs of Nias are zoned as plantation reserve and remain unoccupied, as they are a high hazard area for tsunamis. The Advisors suggest that these areas are used productively as coconut tree plantations, along with cocoa or other suitable bushy plantation trees beneath the coconut trees. 8.3 BUILDING DESIGN AND CONSTRUCTION Indonesia has very good earthquake design codes for buildings but they are often disregarded, even by government institutions, and are seldom enforced. It is particularly important that public buildings should be functional and not damaged after an earthquake and all other buildings may be damaged but should not collapse and kill people. We recommend the following course: Buildings which are required to be fully functional after an earthquake are hospitals, clinics, community buildings, schools, and Government Buildings. Hospitals and clinics are needed to be operational to treat injuries, schools, community and government buildings are often need as evacuation centres for displaced people. All these buildings ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 74 of 80 should be designed and constructed to the highest earthquake resistant standards so that they are undamaged and functional after the design hazard events. All other buildings should be at least of a standard where some damage may have occurred, but the building will not collapse and kill people. In many regions there is a need for such regulations and designs to be prepared and enforced. Low-cost housing programmes should always incorporate disaster resistant construction techniques. Traditional building techniques with disaster resistant characteristics such as those of Nias, can be promoted. As well, houses and other buildings can be built of earthquake resistant materials, such as wood, steel, panels and properly reinforced and constructed concrete, rather than stone or brick masonry. 8.4 REVISIONS TO NIAS BUILDING REGULATIONS (PERDA) In addition to the “bottom up approach” of trying to influence stakeholders involved in building construction that quality of design and construction needs to be improved in order for buildings to be be able to withstand future earthquakes PEMDA needs to revise the existing regulation - Keputusan Bupati Nias Nomor: 188.342/1530/K/2003 Tentang Petunjuk Teknis Pelaksanaan Tata Cara Pemungutan Retribusi Izin Mendirikan Bangunan”. In particular PEMDA needs to have supporting regulations that are consistent with central government legislation. This requires a differentiation between: • • Buildings not requiring specific design – these are defined in UU28-2002 as private dwellings of not more than one floor, and Buildings requiring specific design – these are defined as private dwellings more than one floor and ALL public buildings The IMB implementation procedures need to deal with both categories. For buildings requiring specific design, at the very least PEMDA needs to ensure that suitably qualified individuals have undertaken the design and taken responsibility. UU2002 requires these buildings to be reviewed within PEMDA by a “Tim Teknis” (Technical team). 8.5 BUILDING CONSENTS It is lamentable that most buildings that have been constructed on Nias since the earthquakes and tsunamis of 26 December 2004 and 28 March 2005 do not have building consents (i.e. Izin Membangun Bangunan or IMB in Bahasa Indonesia). Although it can be argued that reconstruction work was required to proceed at such a pace that PEMDA did not have the capacity to issue permits at the rate that was required to support the reconstruction efforts. The danger is that if BRR does not support PEMDA in changing this situation the general populace will have been given the message that it is not important to follow building regulations. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 75 of 80 The Advisors recommend that BRR make this an immediate priority to provide assistance to PEMDA in developing proper procedures, capacity building of PEMDA staff involved in the vetting of building designs and construction. It is the belief of the UNDP Earthquake Advisors that a sustainable approach to the improvement in building quality standards is required. The improvement of building standards on Nias (as elsewhere in Indonesia) requires: • • “Bottom up approach” – through the education of the participants in the building process and the dissemination of information and materials aimed at changing building work practices “Top down approach” – through appropriate building standards and regulations together with an effective mechanism for the technical evaluation of proposed building plans and inspections to ensure that the agreed plans are followed. In addition the implementing authority must have the ability to impose penalties on those who build without consent or do not follow the agreed plans. There have been various initiatives related to the “bottom up” approach such as: • • • Publication of Manual Bangunan Tahan Gempa (rumah Tinggal) by Teddy Boen of ITB in 1983 – this is an excellent guideline which demonstrates with numerous diagrams the principles of good construction. Book entitled Buku Pegangan Disain dan Konstruksi Bangunan Rumah Sederhana yang Baik di Pulau Nias by Robin Willison of UNDP in 2006. This guideline attempts to demonstrate in pictorial form examples of good and bad building practice. ARCLI – an initiative established by GTZ Consultants of Germany together with assistance from Holcim Cement. ARCLI operates in Aceh and attempts to provide guidance in good concrete construction building practice These initiatives are all very useful but need to be accompanied by the updating of PEMDA Nias Building Regulations together with the application of an effective system for building consents accompanied by enforcement. Since the earthquakes of 26 December 2004 and 28 March 2005 due to the outpouring of aid from international donors construction of replacement houses, schools, hospitals and other buildings has proceeded at a much more rapid rate than ever before. Unfortunately, in the haste to reconstruct buildings established procedures for building consents have not been followed by most of the agencies involved in reconstruction. Unfortunately the current situation is that most of the buildings being built around Nias do not have IMBs. There are also instances of building permits being issued but the agreed designs not being followed. Although PEMDA has the authority under the Indonesian Building Code to impose penalties and even to demolish buildings that do not have IMBs PEMDA is reluctant to exercise this authority particularly when the buildings have been funded by well meaning overseas agencies. It is important, however, that the law is upheld and a building consent process is implemented. PEMDA is unable to do this without the support of BRR. Given the limited ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 76 of 80 time remaining for BRR on the island of Nias (until 2009) it is important for BRR to concentrate on preparing for a time when BRR will not be in Nias and PEMDA will need to have the capacity to fulfill its obligations under the Indonesian Building Code. If this is not achieved the message to all will be that it is not necessary to follow building standards, i.e. everyone is free to do what is right in their own eyes. The time has now come for BRR to take active steps toward working closely with PEMDA to assist in the implementation of an effective Building Consent system. This will need to include assistance in: • • • • Revision of Nias Building Regulations Developing appropriate check forms Community socialisation Capacity building Any move by PEMDA to tighten up on the issuance of building consents may well be met with resistance by the local community. I would like therefore to suggest that this needs to be undertaken as part of a broader initiative where PEMDA can be seen by the community as “adding value” and not just charging fees with no perceived benefit. There is a very definite need for the dissemination of information on sound building techniques particularly, but not only, related to earthquake resistance. One way of trying to overcome this would be to establish a Centre of Building Excellence in Gunung Sitoli and in Teluk Dalam that would be tasked with the : • • • • • • Issuance of Building Consents (IMBs) Provision of literature on sound building techniques (e.g. Teddy Boen and Robin Willison’s books) Community socialization of good building practices Facilitate training of “tukang”s Maintenance of proper records related to each building (required by UU36-2005) Field quality verification of designs The followed support is required to assist KIMPRASWIL: 1. The drafting of revised Guidelines for Building Construction (To replace Keputusan Bupati Nias Nomor: 188.342/1530/K/2003 Tentang Petunjuk Teknis Pelaksanaan Tata Cara Pemungutan Retribusi Izin Mendirikan Bangunan”. In particular PEMDA needs to have supporting regulations that are consistent with central government legislation. This requires a differentiation between: • • Buildings not requiring specific design – these are defined in UU28-2002 as private dwellings of not more than one floor, and Buildings requiring specific design – these are defined as private dwellings more than one floor and ALL public buildings The IMB implementation procedures need to deal with both categories. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 77 of 80 For buildings requiring specific design, at the very least PEMDA needs to ensure that suitably qualified individuals have undertaken the design and taken responsibility. UU2002 requires these buildings to be reviewed within PEMDA by a “Tim Teknis”. 2. Capacity Building related to: • • • Understanding of all relevant Indonesian regulations Training of those involved in building structure review Training of those involved in Field inspections 3. GIS mapping and property information database. 4. Training materials 8.6 CONSTRUCTION OF CIVIL INFRASTRUCTURE (ROADS, BRIDGES, PORTS, AIRPORTS) 8.6.1 Bridges More attention in future needs to be given to the design of bridge sub-structures to prevent the occurrence of abutment and pier foundation failures such as has been described in Section 7.3 of this report. More attention in future bridge design needs to be given to: • • • Compaction of road approaches Pile depths Connections of bridge superstructures to abutment seatings Also more attention needs to be given to maintenance such as cleaning and plastering where reinforcing steel has become exposed and is rusting. 8.6.2 Roads Earthquake damage to roads was caused mainly by differential settlement of the road in soft ground areas, landsliding, generally as slow moving landslides and slumps in the steep hills. However, in many places the roads were in very poor condition before the earthquake. A very common problem on many of the roads in Indonesia is poor drainage leading potholes. It is very important that road shoulders and side drains are regularly maintained so that water does not pond on the side of the road, leading to weakening of the ground and breaking up of the road. Regular maintenance is far cheaper than new road reconstruction. Extra care has to be taken with drainage to ensure that poor drainage does not promote slope instability along the roads. “Bio-engineering” or using trees and vegetation to help stabilize marginally stable areas could also be used to help prevent damage to roads and infrastructure in these steep, hilly parts of Nias. Many landslides are initiated and kept ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 78 of 80 moving by groundwater. In these cases drainage is often a practical, cheap and effective method for stabilizing slopes. Often drainage and/or bio-engineering using vegetation and trees are very effective and practical ways of dealing with slope instability in difficult terrain. 8.6.3 Gomo Road There is a section of this road which passes under a very steep bluff and requires widening. The Advisors reviewed several options and these were presented in the report attached as Appendix B. The conclusion presented was that the most practical and cost effective option which uses readily available technology is to construct a gabion mattress wall, similar to the gabion wall already constructed at the nearby washout. If this option was chosen, it appears that the wall could be surveyed, designed and constructed within about 3 months. 8.6.4 Wharves And Jetties Internal corrosion of the reinforcing steel in reinforced concrete wharves seems to be a common problem in Indonesia. This needs to be recognized so that the new wharves under construction are built with good sand and aggregated to make dense concrete which has adequate cover over the reinforcement. As well there are concrete additives that should be used to help prevent corrosion of the reinforcing steel. 8.7 DISASTER PREPAREDNESS It is recommended that PEMDA institute a tsunami warning system for Nias – not for the local great earthquakes which people feel very strongly and where people have 5 to 10 minutes to evacuate after the shaking stops, but for distant earthquakes which may not be strongly felt on Nias and where the time before the tsunami arrives is more than half an hour. It is also recommended that PEMDA Nias and Nias Selatan institute a regulation framework such as has been prepared by the Sleman Kabupaten in Yogyakarta province Following the example of Sleman Kabupaten in Yogyakarta province, an institutional regulation framework is planned for adoption by the two Kabupatens of Nias. In order to deal with emergencies caused by regular eruptions of Merapi volcano, Sleman has district regulations setting up an emergency management unit and its operations, including evacuations and emergency shelters, during a volcanic eruption. ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 79 of 80 APPENDICES A. GEOLOGIC MAP OF NIAS ISLAND QUADRANGLE B. MMI DESCRIPTIONS AND INTENSITY SCALE C. GOMO ACCESS ROAD REPORT D. WEST SUMATRA RECONNAISANCE VISIT E. POTENTIAL AGGREGATE (SAND, ROCK AND CRUSHED ROCK) SOURCES ON NIAS FOR TSUNAMI AND EARTHQUAKE RECONSTRUCTION F. FIELD VISIT REPORT 1-FEB-07 G. FIELD VISIT REPORT 24-FEB-07 H. FIELD VISIT REPORT 27-FEB-07 I. PERATURAN DAERAH KABUPATEN NIAS TINGKAT II NIAS NOMOR 16 TAHUN 1998 J. PERATURAN BUPATI SLEMAN NOMOR 7/Per.Bup/2006 TENTANG SATUAN PELAKSANAAN PENANGANAN BENCANA, DAN KEPUTUSAN BUPATI SLEMAN NOMOR: 5/Kep.KDH/A/2006 TENTANG RENCANA OPERASIONAL PENANGGULANGAN BENCANA GUNUNG API PERAPI K. A CONCEPT ON PREVENTION AND MITIGATION FROM RISK OF TSUNAMI DISASTERS ____________________________________________________________________________________________ FINAL REPORT – UNDP EARTHQUAKE ADVISORS Page 80 of 80