Magnitude 7.6, Sumatra, Sept 30 2009
Where do Earthquakes Occur?Marshak
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Where do earthquakes occur?A closer look Faults Listric faults (large landslides: gravitational collapse of volcanic edifices)Around VolcanosAnthropogenic Earthquakes Collapse of mine shafts Explosions
The Kursk DisasterOn August 12, 2000 the Russian Oscar-Class Submarine, Kursksank, killing all aboard What happened (and what does this haveto do with earthquakes)?Seismology (the study of earthquakes) gave clues about what happened.Russian officials later admitted that the disaster was the result of a faulty torpedo.Lesson: You Cant Hide Big Explosions
October 8, 2006North Korea Nuclear Test
Earthquakes come in all shapes and sizesMarshakRight vs. Left Lateral
INTENSITY: Amount of ground motion = Destructive PowerQualitative measurement depends on:MagnitudeDistance from focusDepth of focusRock typeBuilding type
MAGNITUDE: Quantitative measure of the amount of energy released. The Richter Scale is logarithmic.
Did you feel it?earthquakes.usgs.gov
The Richter Scale is Logarithmic
Press and Siever
How Big is Big?If the ENTIRE San Andreas Fault ruptured at once
Sheet1
Displacement (cm)Magnitude# of Hiroshima Bombs
507.571.54E+04
1007.783.09E+04
2007.986.18E+04
3008.099.26E+04
4008.181.23E+05
5008.241.54E+05
6008.291.85E+05
7008.342.16E+05
8008.382.47E+05
9008.412.78E+05
10008.443.09E+05
Percent Chance of a strong to great earthquake in the next 30 years along the San Andreas Fault
What happens during an earthquake?
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What happens during an earthquake?Marshak
May 24, 2006 Magnitude 5.4
MarshakSurface Rupture
What happens during an Earthquake?Kobe, JapanJanuary, 1995Magnitude 6.9
SEISMIC WAVESThe energy of an earthquake is dissipated by wavesP (primary) WavesCompressionalPush-pull motionTransmitted through liquidsS (secondary) WavesShearSide-to-side (and up-and-down) motionSlower than P wavesNot transmitted through liquidsSurface WavesRayleigh waves (rotational motion, think waves in water)Love waves (Side-to-side motion)
P WavesS WavesMarshak
Rayleigh WavesLove WavesMarshak
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*Earthquakes occur along plate boundaries, MOST OF THE TIME. However, earthquakes can occur anywhere.One of the interesting things is how in some places earthquakes deepen as you go away from plate boundaries These occur along subduction zones. Why?*************************
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