(All shook up.)
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Usually happen near faults. (What are faults?)
Many faults are near plate boundaries, but they can
be anywhere and everywhere.
Over one million earthquakes per year (one every
thirty seconds).
Most are too small to be felt.
But, there are several hundred powerful, damaging
ones per year.
P-Waves
S-Waves
L-Waves
(aka Surface Waves)
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Measures the
magnitude
(amount of energy
released).
0-10 scale.
Devised by
Charles Richter in
1935.
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It goes up
exponentially.
Going up one whole
number means a ten
times more powerful
quake!
So going up two whole
numbers means a 100
times more powerful
quake!!
By far the most destructive of all
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Happen at subduction
zones.
Since 1900, all six 9.0 or
greater quakes.
Can produce tremendous
tsunamis (ex. Southeast
Asia in 2004 and Japan in
2011)
The Cascadia Subduction
Zone is a very likely spot
for a megathrust and a
tsunami.
Click on image for short
video (0:28)