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Chapter 6 C3
Earthquakes
Case History
C3 C3On January 12, 2010 a magnitude 7.0 earthquake struck Haiti and killed about 300,000 people CA magnitude 6.3 earthquake struck the midlevel town of L'Aqila- in 2009, many of the buildings collapsed, killing about 300 people. A similar earthquake inCalifornia probably would have caused no or very few deaths CIn Chili (February 27, 2010), a magnitude 8.8 earthquake, about 500 times as strong as the Haiti50 earthquake, killed about 800 people CBuildings are not designed to withstand shaking or are built improperly, causing far more deaths
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Earthquakes
caused
CViolent ground-shaking phenomenon'by the sudden release of strain energy stored in rocks COne of the most catastrophic and devastating hazards C?Globally, most earthquakes areconcentrated along plate boundaries CUSGS estimated about 1 million_quakes annually C3Millions of people I killed and billions of dollars in damage by catastrophic earthquakes
Causes for Earthquakes
C3
c3Stress and strain
C? Stress : A force exerted per unit area within rocks or other Earth materials C? Strain : Deformation (size, shape, and orientation) of rock materials_ caused by stress C3_Rock strength_: Rock's ability to stand a withstand magnitude level of stress before rupture CEarthquake: Strainaccumulatedbeyond rock strength
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Causes for Earthquakes
C3
CEarthquake: Sudden release of strain energy caused by rock rupture - (through faulting) cEarthquakes induced by human activities CMuch smaller magnitude C3Reservoir -induced earthquakes CDeep waste disposal_and earthquake CNuclear explosions
Earthquake Magnitude
to produce the earthquake
63 Epicenter: The location on the surface _ of Earth above the focus
by the earthquake. Mw = 2/3 log M0 - 10.7, where Mo is the seismic moment, estimated by examining the records from seismographs C Richter magnitude: Named after the famous
released by an earthquake. It is based upon the amplitudeor size of the largest seismic wave produced by an earthqua