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How are Seismic Waves caused?
-When energy is released, during an earthquake, as a fault ruptures.
-radiate away in all directions from the focus (hypocenter)
: 1) body 2) surface
-2 types of body waves 1) Primary(travels faster) 2)Secondary waves( arrive second)
-recorded on seismographs
Modified Mercalli Intensity scale
evaluate the effects of earthquakes, based on observed effects
Why moderate sized quakes don't relieve the stress (and prevent) a larger quake
Loma Prieta was not "The big one" nor will it prevent it
Characteristics corresponding to magnitude
1) Longer length of rupture, larger the magnitude
Fault segmants and their "characteristic magnitude"
2) More offset, larger magnitude
3) Larger magnitude
: longer shaking (also related to groundtype)
Geologic factors which affect level of earthquake damage
1) Magnitude of the earthquake
2) distance from the epicenter/ fault
3)local "ground" type
: solid rock or
unconsolidated ground ex
: Alluvium (amplifies shaking; may liquefy
4) Duration of shaking
5)Focusing of the seismic waves
Why do some areas have higher damage than expected (on their basis of their distance from the epicenter)?