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Determining the location of the focus
- Body waves (goes through the body of the earth): *P-waves travel faster the S-waves, so they arrive before
- -measure arrival of P & S waves=distance from the epicenter to the station
- -primary and secondary
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Why can't moderate-sized earthquakes relieve the stress and thus, prevent a great earthquake?
- -it would take about 1,000 quakes to release the amount of energy of an M=7 quake. (1 increase in magnitude results in an increase of about 31 times in the energy released)
- -loma Prieta quake did very little to relieve the stress build-up in the rocks in the San Francisco area as it builds toward "The Big One"--the quake of a magnitude similar to the 1906 San Fran quake which is expected w/in the next 30 yrs
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Characteristics of Magnitude
- 1) longer length of rupture,larger magnitude
- 2)More Offset, larger magnitude
- 3)Larger Magnitude, longer shaking
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Alaska-Seismic risk zone
- -2nd largest earthquake ever recorded 1964
- -8.3 magnitude
- -3-4 minutes
- -11 aftershocks of magnitude greater than 6.0
- -caused vertical displacement
- -produced a tsunami
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