Earthquake Prediction and Control
1. Long term monitoring/forecasting:
Use of Paleoseismology:
Seismic gaps - A seismic gap is a zone along a tectonically active area where no earthquakes have occurred recently,
but it is known that elastic strain is building in the rocks. If a seismic gap can be identified, then it might be an area
expected to have a large earthquake in the near future.
Short-term predication involves monitoring of processes that
occur in the vicinity of earthquake prone faults for activity that
signify a coming earthquake.
Precursor events signal a coming earthquake;
These events are processes that happen before an earthquake
takes place and include:
Ground uplift and tilting due to swelling of rocks caused by
strain building on the fault.
May lead to numerous small cracks (microcracks), which in turn
can lead to foreshocks (small earthquakes).
Foreshocks - Prior to a 1975 earthquake in China, the observation of
numerous foreshocks led to successful prediction of an earthquake and
evacuation of the city of the Haicheng. The magnitude 7.3 earthquake that
occurred, destroyed half of the city of about 100 million inhabitants, but
resulted in only a few hundred deaths because of the successful evacuation..
Water Level in Wells - As rocks become strained in the vicinity of a fault,
changes in pressure of the groundwater (water existing in the pore spaces
and fractures in rocks) occur. This may force the groundwater to move to
higher or lower elevations, causing changes in the water levels in wells.
Emission of Radon Gas - Increases in the amount of radon emissions have
been reported prior to some earthquakes.
Changes in the Electrical Resistivity of Rocks - In some cases a 5-10%
drop in electrical resistivity has been observed prior to an earthquake.
Strange Animal Behavior - Prior to a magnitude 7.4 earthquake in Tanjin,
China, zookeepers reported unusual animal behavior. Snakes refusing to go
into their holes, swans refusing to go near water, pandas screaming, etc.
Earthquakes may cause both uplift and subsidence of the
Hazards Associated with Earthquakes
These men barely
► Ground escaped when the front
Shaking of the Anchorage J.C.
Intensity of ground during the 1964 Good
shaking depends on: Friday earthquake
► Local geologic
conditions in the area.
► Size of the Earthquake.
► Distance from the
► Damage to structures
from shaking depends
on the type of
One side of this Anchorage street
dropped drastically during the 1964
Good Friday earthquake.
San Francisco Bay
Prieta EQ, These buildings in Japan toppled
1989 when the soil underwent
A section of freeway
880 collapsed where
anchors were placed in
Soft mud along the edge of San Francisco Bay amplified the
ground motion under the freeway by a factor of 5 to 8 despite the
90 km -distance to the epicenter.
Loma Prieta earthquake, 1989
Earthquake-induced landslide damage to
a house built on artificial fill, after the The 2001 El Salvador earthquake-induced
2004, Niigata Prefecture, Japan landslide located in a neighborhood near San
earthquake. Photo by Prof. Kamai, Kyoto Salvador, Santa Tecla. Photo by Ed Harp,
Univ., Japan. USGS - for more information and photos
please see this publication:
1906 San Francisco Earthquake
1923 Great Kanto
There are two classes of earthquake effects: direct, and secondary.
Direct effects are solely those related to the deformation of the
ground near the earthquake fault itself. Thus direct effects are limited to the
area of the exposed fault rupture.
Most of the damage done by earthquakes is due to their secondary
effects, those not directly caused by fault movement, but resulting instead
from the propagation of seismic waves away from the fault rupture.
•triggering of aftershocks and additional earthquakes.
Earthquakes don’t kill people,
falling buildings and highway
Most of the hazards to people
come from man-made
structures themselves and
the shaking they receive
from the earthquake. The
real dangers to people are
being crushed in a collapsing
building, drowning in a flood
caused by a broken dam or
levee, getting buried under a
landslide, or being burned in
Earthquake hazard risk depend on
► Location of critical facilities
► Construction standards (building codes)
► Emergency preparedness
Landuse planning and building codes are the best
defenses against death, injuries and property
- should limit development in areas along active faults, situations
prone to landslides or on soft mud
Example Armenian earthquake, 1988
Source: Modified after: www.gadr.giees.uncc.edu/PPT_SLIDES/SPITAK%20EARTHQUAKE.ppt
SPITAK EARTHQUAKE: UN-
ANCHORED FLOOR PLANKS
SPITAK EARTHQUAKE: UN-
SPITAK EARTHQUAKE: UN-
CONCRETE FRAME BUILDINGS
SPITAK EARTHQUAKE: NEW
SPITAK EARTHQUAKE: DEBRIS
AND TRAFFIC HINDERED EM
RECONSTRUCTION COSTS OF ABOUT
SPITAK EARTHQUAKE: SEARCH
MEDICAL SERVICES WERE UNAVAILABLE IN THE
HOUR OF GREATEST NEED.
Lessons learned after the
THRUST FAULTS” WERE
► THE“NEW” SPITAK IS A 4-STORY
CITY WITH MUCH MORE STEEL
EMERGED AS A HIGH PRIORITY