Earthquake prediction Earthquake hazards

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Earthquake predictionEarthquake hazards
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Earthquake Prediction and Control

• Long term monitoring/forecasting
• Use of Paleoseismology

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Seismic Gaps
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.
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Short-Term Prediction
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).
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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.
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Ground Deformation
Earthquakes may cause both uplift and subsidence
of the land surface.
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Hazards Associated with Earthquakes
These men barely escaped when the front of the
Anchorage J.C. Penny's collapsed during the 1964
Good Friday earthquake

• Ground Shaking
• Intensity of ground shaking depends on
• Local geologic conditions in the area.
• Size of the Earthquake.
• Distance from the Epicenter.
• Damage to structures from shaking depends on the
  type of construction.

One side of this Anchorage street dropped
drastically during the 1964 Good Friday
earthquake.
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• Liquefaction

San Francisco Bay
Loma Prieta EQ, 1989
These buildings in Japan toppled when the soil
underwent liquefaction.
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A section of freeway 880 collapsed where anchors
were placed in soft mud.
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
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Landslides
Earthquake-induced landslide damage to a house
built on artificial fill, after the 2004, Niigata
Prefecture, Japan earthquake. Photo by Prof.
Kamai, Kyoto Univ., Japan.
The 2001 El Salvador earthquake-induced landslide
located in a neighborhood near San Salvador,
Santa Tecla. Photo by Ed Harp, USGS - for more
information and photos please see this
publication http//landslides.usgs.gov/research/o
ther/centralamerica.php.
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• Flooding

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Fire
1906 San Francisco Earthquake
1923 Great Kanto Earthquake
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• 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.
• Secondary Effects
• 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.
• seismic shaking
• landslides
• liquefaction
• fire
• flooding
• triggering of aftershocks and additional
  earthquakes.

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• Earthquakes dont kill people, falling buildings
  and highway structures do.
• 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 a fire.

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Community Adjustments

• Earthquake hazard risk depend on
• Location of critical facilities
• Construction standards (building codes)
• Emergency preparedness

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Landuse planning and building codes are the best
defenses against death, injuries and property
damage. Zoning - should limit development in
areas along active faults, situations prone to
landslides or on soft mud Example Armenian
earthquake, 1988
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Armenia Earthquake, 1988
Source Modified after www.gadr.giees.uncc.edu/PP
T_SLIDES/SPITAK20EARTHQUAKE.ppt
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Spitak Earthquake
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SPITAK EARTHQUAKE UN-ANCHORED FLOOR PLANKS
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SPITAK EARTHQUAKE UN-REINFORCED MASONRY
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SPITAK EARTHQUAKE UN-REINFORCED MASONRY
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SPITAK EARTHQUAKE CONCRETE FRAME BUILDINGS
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SPITAK EARTHQUAKE NEW BUILDINGS PERFORMED POORLY
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SPITAK EARTHQUAKE CULTURAL HERITAGE
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SPITAK EARTHQUAKE DEBRIS AND TRAFFIC HINDERED EM
RESPONSE
RECONSTRUCTION COSTS OF ABOUT 16 BILLION
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SPITAK EARTHQUAKE SEARCH AND RESCUE
MEDICAL SERVICES WERE UNAVAILABLE IN THE HOUR OF
GREATEST NEED.
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Lessons learned after the SPITAK EARTHQUAKE

• BLIND THRUST FAULTS WERE AVOIDED
• THE NEW SPITAK IS A 4-STORY CITY WITH MUCH MORE
  STEEL
• EARTHQUAKE ENGINEERING EMERGED AS A HIGH PRIORITY