A Brochure for Earthquake Disaster Prevention Prelude As the Chiayi Rueili earthquake occurred on July 17, 1998, I remember at that time I was in my office, which is on the 19-th story. Even though the earthquake intensity was not very large at Taipei, I still could explicitly feel the shaking of the building and was shocked by the shaking both physically and mentally. Immediately following the earthquake, damages to house, hotel, school building and bridge were reported. In addition, 5 people were killed. In the next few days, the rescue was continued and it is very concerned about whether it is an indication for a severe earthquake after a lot of aftershocks. Similar to the typhoon or ocean wave, the earthquake is a part of the natural activity. However, it is a pity that up to now no one around the world can reliably predict the occurrence of an earthquake with the right time, right location and right magnitude as those predicted for a typhoon. Consequently, the earthquake still gives a great threat for the people resided in Taiwan, such as those resided in Tokyo and Kobe, Japan, as well as in Los Angeles and San Francisco, U.S.A. since all these areas are located on the collision boundary of the Eurasian plate. Although earthquake is unpredictable the damage to life and property can still be minimized based on the technology developed in Taiwan if the earthquake prevention is well prepared and the emergency response is appropriately taken. National Science Council of the Republic of China continues its full support for the research on seismology and earthquake engineering. In addition, the National Center for Research on Earthquake Engineering (NCREE) was founded a few years ago. A large structural laboratory was constructed for the improvement of earthquake resistant design and the development of new technology for seismic isolation. The content of this brochure is the research results regarding to the earthquake itself and its damage prevention from the specialists in the Academia Sinica and in the ministry of economic and transportation. Hopefully, this brochure can effectively alleviate the earthquake damage to life and property after reading of it since one can well prepared for earthquake disaster after recognizing the possible damages caused by an earthquake. Knowledge and action are the best prevention when you face an earthquake. Best wishes! Catalogue 1. Prelude 2. Organization and Strategy for Earthquake Disaster Prevention and Rescue l Organization for Catastrophic Disaster Prevention and Rescue l Community Organization for Disaster Prevention and Rescue l Guidelines to Reduce Earthquake Damage for Individuals 3. Failure Modes of Buildings under Seismic Loading Appendix 1. Seismic Hazard in Taiwan Area 1. Introduction On July 17, 1998, an earthquake occurred at the Chiayi County with a magnitude of 6.0 on the Richter scale. Since this earthquake is the only earthquake that caused a severe damage and even the death of people for the recent 30 more years in the area of Chiayi-Tainan in Taiwan it attracts much attention. In fact, the seismic activity in this area is widely discussed after a long period of inactivity. Because this event is a very shallow earthquake the ground shaking near the epicenter is tremendous and thus the damage to buildings, bridges and roads is inevitable. Since the tectonic movement continues the seismic activity in Taiwan area will never be stopped. In fact, an earthquake will occur after the energy is accumulated to be large enough. Even though the capability to earthquake resistance of a structure is significantly improved an earthquake with a magnitude over 7.0 might still lead to a catastrophic disaster and the damage may be more severe than that caused by any of the pass earthquake events. This brochure is proposed to provide the general public with the awareness of an earthquake and the simple guidelines to respond with the earthquake disaster. Hence, if one has the earthquake preparedness in advance, appropriately responds during the earthquake and takes the right actions after the event the earthquake damage then can be effectively minimized. 2. Organization and Strategy for Earthquake Disaster Prevention and Rescue (a) Organization for Catastrophic Disaster Prevention and Rescue In order to mitigate the threat from an earthquake, all levels of the government in the world will generally raises the importance of damage prevention before the quake, emergency response and rescue during the quake and the recovery after the quake. As a result, the organization for disaster prevention and rescue is founded. In Taiwan, these organizations were set up from the central to local governments since 1994. In addition, the meeting is regularly held by each level of government to propose the plans for disaster prevention and rescue. These plans can be considered as the guidelines for the disaster prevention before an earthquake, for the emergency response and rescue in an earthquake and for the recovery after an earthquake. As a catastrophic disaster occurs, the procedure to damage prevention and rescue will be preceded by the government as follows: (a-1) The government infrastructure for disaster prevention and rescue, such as the fire fighting department and the police department, should collect the information about the emergency faced and go to the rescue immediately. (a-2) Report the damage to the authorized government agencies. Then, they will organize a team to respond with rescue and recovery operations according to the plan for emergency response. (a-3) The authorized government agency should report to the responsibilities of the district administrator to establish the “Emergency Response Center” for the emergency management and rescue. (a-4) If the government infrastructure cannot handle the disaster rescue or recovery it should make a request for assistance from the higher level of government. The level of government to assist the emergency response and rescue is dependent upon the actual need of emergency faced. (b) Community Organization for Disaster Prevention and Rescue Disaster prevention and rescue involves every one, family and community. In addition, community organizations for disaster prevention and rescue are the basis of the national organization for disaster prevention and rescue. They can reduce the causes to disasters in the usual time and in a disaster they will go to rescue first. In fact, in case of disaster the elected district administrators, such as town supervisors or village executives, should assemble their members to involve the immediate rescue. This may include emergency medical services, fire fighting, shelter, food, water and essential services. A well-coordinated emergency response to an earthquake is likely to save many lives and prevent earthquake-induced hazards escalating the magnitude of the disaster. (b-1) Development of the Community Organizations: It is necessary to set up a community organization for disaster prevention and rescue based on the conditions and needs of the specific district region. The following skeleton is used to Supervisor illustrate a possible community organization. food supply Casualty Savage information report shelter guide fire fighting (b-2) Emergency Preparedness: Community organizations can promote participation in emergency preparedness activities and help organize practice drills and exercises to raise awareness and ensure that everyone knows what to do. In addition, a community disaster plan can also be drawn up, involving fire-fighting, search and rescue, first aid, making contact with authorities, supervision of food, water and power provisions. (b-3) Emergency Response: Pre-earthquake emergency planning is one of the best ways to ensure that the earthquake disaster can be handled effectively. In fact, as a disaster occurs, using this plan with the usual practice drills and exercises for emergency response and rescue. (b-4) Recovering from Earthquakes Fit in with the government to gather data on the extent of damage and its distribution in the community. In addition, help each other to recover from the disaster. If the earthquake causes people injured or a great loss, make a request for assistance from the local government or call 119 for help. 3. Guidelines to Reduce Earthquake Damage for Individuals (a) Before the Earthquake (a-1) At Home (a-1-1) Reinforcing shelving, fixing tall furniture to the wall and keeping items low and safe will make your living environment a safer place. (a-1-2) Recognizing the shelters and their routes both at home and nearby. (a-1-3) Recognizing the place of switch for gas and electricity and how to turn off. (a-1-4) Preparing an emergency box and fire extinguishers. Let all the family members know where they located and how to use them. (a-1-5) In case of any problem in the building, ask licensed engineers or agencies to check and retrofit it. (a-1-6) Check the equipments for fire fighting and exercise the plan for disaster prevention and rescue regularly if you are living in a high-rise building. (a-2) In the Public Place (a-2-1) Propose an emergency plan and assign the staffs or servers to take in charge of the disaster prevention and emergency response. (a-2-2) Check the equipments for fire fighting regularly. (a-2-3) Exercise the disaster prevention regularly. (a-2-4) Check the billboard and the shelter from the sun or any other potentially dislodged item constantly. (b) During the Earthquake (b-1) indoors (b-1-1) Turn off gas, electricity and water supplies. (b-1-2) Using an appropriate exit to keep away from any congestion in a public place. (b-1-3) Open the door in order to avoid that the door is jammed by the large deformation in an earthquake. (b-1-4) Stay away from the glass window and find a safe shelter. (b-1-5) Sit or lie down beside or underneath a table or bed to protect against possible objects falling from above. (b-1-6) Keep calm and do not rush out in panic. (b-1-7) In case of fire put it out right away. (b-1-8) Do not use the elevators but use the stairs. (b-2) outdoors (b-2-1) If you are driving a car or riding a bike do not stop immediately. In stead, drive the car or ride the bike to the roadside and then find a shelter. (b-2-2) If you are walking in the street, run into an open space or the pedestrian corridor. (b-2-3) Keep away from the gas station, glass curtain wall, vending machine, electric pole and construction site, etc. (b-2-4) Look out for any possible objects falling from above and put your arms on your head. (b-2-5) If you are on a bus or a train, do not panic and jump outside. Stay in the bus or train temporarily and put your arms or a bag on your head. (b-2-6) If you are in a suburb, stay away from the hill, riverside and seaside and find an open space for shelter. (b-2-7) If you are on a viaduct or an underground passage, walk away calmly and immediately. (c) After the Earthquake (c-1) Help each other for the disaster rescue. Have a look at the other buildings nearby. Their occupants may need your help. (c-2) If electric power is recovered after the power shutdown, do not use any electric devices right away but check first whether there is a leak of gas to keep away from any explosion or fire. (c-3) Listening to the radio or watching TV any time and escaping from any rumor. (c-4) Do not use the telephone unless somebody has been injured or a building is damaged or burning. The emergency services may need all lines for the rescue. (c-5) Inspect the house for cracks. If beams or columns are damaged leave the house as soon as possible and ask a civil agency to inspect and restore. (c-6) If the gas pipeline is damaged or there is a smell of gas, do not use any gas or electric devices. Open the doors and leave the house immediately. In addition, report to the authority. 3. Failure Modes of Buildings under Seismic Loading The habitation is always closely related to the human beings. Ancient people resided in caves to shelter from the wind and rain. Following the progress in the civilization of human beings, the construction materials for buildings are gradually improved in the order of timber, rock, brick, reinforced concrete and steel. All the buildings are located on the ground or even fixed into the ground. Therefore, when a building is excited under an earthquake, its base tends to move with the ground where it is supported. Taiwan area is in the time of high potential of the occurrences of earthquakes. Furthermore, it can be expected that a lot of structures will be destroyed to a different degree of damage if a strong earthquake occurs at the present time. Some will be totally collapsed and some may be damaged and need to be retrofitted. However, each structure must be well reevaluated by the engineers. The following figures or photos are used to illustrate the general failure modes of buildings under seismic loading. Brittle Failure at the End of a Column Since a reinforced concrete column will in general be subjected to a maximum moment at its ends adequate stirrup reinforcement is needed at the column ends. If the stirrup reinforcement is too short or widely spaced brittle failure may occur at the column end due to the inadequate confinement in longitudinal bar and concrete. If this occurs in several columns of the same story this building may be collapsed at any story. Failure of the Short-Column Type In general, the design of a column is based on its net height. However, the window above half-height in-filled shortens the effective length of the column. This may cause the shear force to be greater than the shear capacity possessed by the column and finally might result in a diagonal shear crack in the column. This is the so-called “short-column” type damage. Punching Shear Failure When two-way slabs are supported directly by columns, such as in flat slabs and flat plates, or when they carry concentrated loads, such as in footings, punching shear near the columns is of critical importance. For the failure of punching shear, the potential diagonal crack follows the surface of a truncated cone or pyramid around the column. Unfixed Heavy Objects in the Top Story During an earthquake, the top story response is generally greater than the low story response and then it will experience a larger seismic force. As a result, if any heavy object in the top story is not fixed tightly it may fails or falls down in an earthquake. Interaction of Axial Load and Side-Sway An axially loaded column accompanying with a side-sway will cause the secondary moment for the column. Thus, the increase of the axial loading may result in the buckling or yielding of the column and eventually the collapse of a whole story. Pounding Failure Individual building need to be provided with adequate separation, to prevent damage caused by pounding when deform in earthquake, which has been a serious cause of damage to multistory structures, even of collapse, in recent earthquakes. The minimum separation gap depends on the height of building and on the flexibility of the building. The gap between buildings should exceed the maximum drift of each story with an extra allowance. Failure of Accessory and Nonstructural Element Accessory of a building such as the water tank, TV and elevator and the nonstructural element such as the curtain wall, interior partition and staircase may be destroyed by the large deformation due to a severe earthquake. Especially, the break of elevator and collapse of the interior partition may damage to life. Failure of the Pre-damaged Structural Element The capability to earthquake resistance of a structural element may be reduced due to the implementation of a nonstructural element. For instance, a drainpipe is usually embedded in the column. Thus, the effective area for the column to resist the axial force is reduced. Furthermore, if there is a leak in the drainpipe the concrete and steel will be corroded with the time passing. Consequently, this structural element will be damaged prior to the other structural elements and may lead to collapse of the whole building. Slope Failure Sloping ground or rock masses, which are stable under normal loading, can lose their stability during an earthquake causing effects from a slow progressive creeping of the ground to dramatic landslide or rock fall. Whether sudden or slow, such slope failures are liable to cause complete destruction of any building founded on them or in the path of the slide. Landslide and later spreads can also cause extensive property damage. Fault Rupture Failure Large permanent ground deformations often occur at the surface associated with fault ruptures in earthquake. Vertical and horizontal displacements have occurred across fault breaks; where this relative movement occurs under a building, a bridge or any structure catastrophic damage can result. Foundation Failure due to Soil Liquefaction Earthquake-induced soil liquefaction has been the cause of catastrophic damage in a number of earthquakes. Certain types of soils, when they are saturated with water and then suddenly shacked by an earthquake, completely lose all shear strength, and flow like a liquid. The support to the foundations of buildings or bridges built on such soils then disappears, and they can plunge into the ground, or be carried sideway bodily on unliquefied masses of soil. Appendix: Seismic Hazard in Taiwan Area 1. Causes of Earthquakes l Distribution of Earthquakes The distribution of earthquakes in the world is well recognized after the study of several decades. It is concluded that earthquake occurrences are not distributed uniformly over the surface of the earth; instead they tend to be concentrated along well-defined lines, which are known to be associated with the boundaries of plates of the earth’s crust. There are three principal world zones or belts of earthquake activity. They are the Circum-Pacific seismic zone, the Eurasian seismic zone and the Mid-oceanic ridge. It is worth noting that some large and highly destructive earthquakes do occur in continental zones but not in the three principal world zones mentioned above. In fact, there are the so-called intra-plate earthquakes, such as the 1812 New Madrid earthquake in Missouri, U.S.A. and the 1976 Tangshan earthquake in China. The island of Taiwan is located at the Circum- Pacific seismic zone and thus seismicity is Northern extremely active in this country. Based on the Earthquake Belt distribution of the recorded earthquakes, Western Taiwan can be roughly divided into three Earthquake Belt seismic zones. They are the northeastern seismic zone, the eastern seismic zone and the western seismic zone as shown in the figure. Eastern Legend Earthquake Most earthquakes occurred in the eastern and Earthquake with Belt Surface fracture western seismic zones are shallow earthquakes while shallow-, medium- and deep-focus earthquakes are common in the northeastern seismic zone. Earthquake with Surface Rupture in Taiwan l Active Fault An earthquake may be induced by many causes, such as volcanic eruptions, the collapse of underground mine-workings, man-made explosions and the fault ruptures. However, the fault rupture causes the most earthquakes and thus is of importance. In fact, about 90% earthquakes are tectonic earthquakes in the world. An active fault implies its recurrent movement for a specific period of time. However, a given time period may not be satisfied for all the users of different purposes under different tectonic settings. Recently, Central Geological Survey has collected all the active fault data in Taiwan area and gives the definition for an active fault. In fact, it will be considered as an active fault if there is recurrent movement in the late Quaternary period. Furthermore, active faults are classified into two categories based on the identified period of last movement. The first category of active faults includes those (1) activated in the Holocene, (2) offset (creep) the man-made structures, (3) relate to recent large earthquakes, (4) offset the recent alluvium and (5) show the creeping phenomena as verified by the present geodetic method. On the other hand, the second category of active faults is those (1) activated within the last 100,000 years or (2) offset the terrace deposits or tableland deposits. In addition, some active faults are not classified into the two categories due to the lack of geologic evidences and are considered as suspect active faults. The distribution of active faults, whose fault trace is greater than 5 km in Taiwan area, is shown in figure with a scale of 1:500,000 geological map. There are 51 active faults in total, 9 are in the first category, 15 are in the second category and Active Faults the rest 27 faults are the suspect active faults. In Taiwan 2. Possible Earthquake Damages The movement of tectonic plates Landslide Surface Rupture may lead to the fault rupture and then results in an earthquake. When the rupture occurs, the release of strain adjacent to the crack surface will be accompanied by a sudden relative displacement of the two sides. Thus, a Landslide Bridge Broken displacement wave is initiated by this rupture and will be propagated radially from the source. Consequently, the severe ground shaking introduced by Tsunamis Building Collapsed the earthquake wave may cause damage to the structure, life and property. In general, earthquake damages can be simply classified into two types, which are the direct and indirect damages. A fault rupture may lead to tsunamis, landslide, large ground deformation, soil liquefaction and then the damage to structures. All these can be considered as the direct damage. On the other hand, the indirect damage implies secondary disasters triggered by the earthquake or the earthquake-induced accidents. Flooding following earthquakes may result from the failures of reservoirs or embankments. The failure of pipeline may lead to a leak of gas or a fire arising from the short circuit. In addition, the overturning of building contents and equipment may also impair life. It should be mentioned that more fatalities are caused by the failure of nonstructural elements or by earthquake-induced accidents than are caused by the collapse of buildings. When the earthquake occurs, it might cause… . Leak of poison gas in factory Catastrophic damage fire The difficulty to resoue The difficulty for fire fighting 3. Earthquake Disasters in Taiwan The history of seismic activity in Taiwan can be dated back to the seventeenth century. Prior to 1897, the historical records of earthquakes are made up of local governmental documents and personal diaries and accounts. In 1897, seismographs were first installed in Taiwan. After the use of seismographic instruments, there were 125 destructive earthquakes between 1898 and 1998. The greatest earthquake is the one occurred on June 5, 1920 at Hualien. The magnitude of this earthquake is as large as 8.0. According to the past earthquake data, the most active seismic zone in Taiwan is near Hualien and Ilan region. Meanwhile, most destructive earthquakes occurred in the western region of Taiwan are in the area of Hsinchu, Taichung, Chiayi and Tainan. Among the 125 destructive earthquakes, 30 events occurred in the western region. Even though the occurrence rate in the western region is lower than that of the eastern region, the earthquake disasters caused in this region are more severe than those of the eastern region. Hence, this needed to be greatly considered in construction. Observing the earthquake events recorded by the seismographic instruments from 1898 to 1998, the magnitude, epicenter, tectonics and building type of the most severe 10 events are different. Thus, each caused a different degree of damage. In general, if the epicenter is in mountainous terrain such as the 1998 Ruilei earthquake, landslide is the major geologic damage. However, in plains the major geologic damages are the fault rupture, surface break, quick sand, and soil liquefaction. What kind of geologic environment is apt The Epicenter Map of the most severe Earthquakes to have above geologic damages? In in Taiwan,1898-1998 plains, the geologic damages such as the offset, surface break and quick sand mainly caused by the fault rupture. Liquefaction is most likely to occur in loose cohesionless soils, such as fine sand or silts; these are most commonly found in sea or river deposited sediments. These geologic damages may lead to the collapse of structures and the destruction of pipelines. Landslides may occur at the steep slopes in mountainous terrain. Thus, it is very important to protect the building and road from rockfalls and mudflows by using a retaining structure.
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