Download - Earth quake
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EARTHQUAKE
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Earthquake
An earthquake (also known as a
quake, tremor or temblor) is the result
of a sudden release of energy in the
Earth's crust that creates seismic
waves. The seismicity, seismism or
seismic activity of an area refers to the
frequency, type and size of
earthquakes experienced over a
period of time.
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What are
Earthquakes? The shaking or trembling caused by the sudden
release of energy
Usually associated with faulting or breaking of
rocks
Continuing adjustment of position results in
aftershocks
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What is the Elastic Rebound Theory?
Explains how energy is
stored in rocks
◦ Rocks bend until the
strength of the rock is
exceeded
◦ Rupture occurs and
the rocks quickly
rebound to an
undeformed shape
◦ Energy is released in
waves that radiate
outward from the fault
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What are Seismic Waves?
Response of material to the
arrival of energy fronts
released by rupture
Two types:
◦ Body waves
P and S
◦ Surface waves
R and L
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Body Waves: P and S waves
Body waves
◦ P or primary waves
fastest waves
travel through solids, liquids, or gases
compressional wave, material movement is in the same direction as wave movement
◦ S or secondary waves
slower than P waves
travel through solids only
shear waves - move material perpendicular to wave movement
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What causes
earthquakes?
Elastic Rebound
Sources of stress
◦ Plate Tectonics
◦ Other stresses
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The Economics and Societal Impacts of EQs
Damage in Oakland, CA, 1989• Building collapse
• Fire
• Tsunami
• Ground failure
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Cause of Earthquak
Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismicwaves that make the ground shake. When two blocks of rock or two plates are rubbing against each other, they stick a little.
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Can Earthquakes be Predicted?
Earthquake Prediction Programs
◦ include laboratory and field studies of rocks before, during, and after earthquakes
◦ monitor activity along major faults
◦ produce risk assessments
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Effects
Rupture
Death
Bldg collapse
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Can Earthquakes be
Controlled?
Graph showing the relationship between the amount of waste injected into wells per month and the average number of Denver earthquakes per month
Some have suggested that pumping fluids into seismic gaps will cause small earthquakes while preventing large ones
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Effects Fires
Liquifaction
Landslides