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EARTHQUAKES Chapter 6 Honors earth science
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http://earthquake.usgs.gov/
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apps Apps Quake Feed Earthquake! Earthquake map and alerts Earthquake- Quake Tracker
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LARGEST QUAKES SINCE 1900 Chile19609.5 Alaska19649.2 Alaska19579.1 Sumatra 20049.1 Japan20119.0 Chile 20108.8
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MAJOR RECENT QUAKES Sumatra 9.1 12/26/04 230,000 Haiti 7.01/12/10316,000 Chile 8.82/27/10 810 Japan 9.03/11/11 28,000 + Chile 8.2 2014 6 Nepal 7.8 4/25/2015 8,000+
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What is an Earthquake? Vibration of earth from rapid release of energy (from plate boundaries) Focus- Epicenter-
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After shocks Smaller quakes following “main shock” Plate readjusting to new location
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faults
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Normal fault tensional stress along divergent boundaries footwall Hanging wall
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Reverse (thrust) fault compressional stress along convergent boundaries footwall Hanging wall
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Strike slip shearing stress along transform boundaries
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San Andreas Fault
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EARTHQUAKE WAVES
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A seismogram records wave amplitude vs. time
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GPS seismometer
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Seismograph
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P waves Primary travel fastest travels through solids AND liquids compressional wave –push/pull
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Primary (P) waves
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S waves Secondary travels only through solids (NOT liquids) Up and down motion
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Secondary (S) waves
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Surface waves Travel on surface slow Movement is similar to water waves
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Michigan quake 5/2/15
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Mantle info: core info: outer= inner=
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A time-travel graph is used to find the distance to the epicenter
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The epicenter is located using three or more seismograph
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INTENSITY OF QUAKE Depends on –energy released (magnitude) –distance from epicenter –rock type (soft=worse) –Depth (shallow=worse)
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SCALES Richter (1935) 1 to ? –each step 10x more energy than previous step Moment Magnitude –Mw –Good for large quakes –Most accurate Mercalli (1902) –measures damage –I- XII
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Who wants to move to CA?
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Intra plate earthquakes Occasionally a quake will occur in the middle of a plate- INTRAPLATE –stress fractures? Ancient faults –Volcanic?
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Michigan earthquakes Year Date Lat. Long. Mag. City 1877 Aug 17 42.40 83.25 3.2 Greenfield 1938 Mar 13 42.08 83.17 3.8 Gibralter 1938 Mar 14 42.08 83.17 ? Gibralter 1947 Aug 10 41.928 85.004 4.7 Coldwater 1977 Oct 26 47.1 87.1 2.7 L Superior 1980 Apr 29 47.2 87.8 0.5 L Superior 1982 Nov 26 42.17 85.48 2.5 Scotts 1994 Sep 02 42.57 84.64 3.4 Central Lansing 2001 Oct 23 42.34 84.76 2.9 Prairie L
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NEW MADRID EARTHQUAKES Magnitude 8.1 (approx) Dec. 1811-1812 5 th worst earthquake in US history Rang church bells in Detroit Made Mississippi River flow backwards
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Earthquake hazards Structural damage –Most common Tsunamis Fires (electrical lines + gas lines) Landslides liquifaction
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Liquifaction
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Formation of a tsunami
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Japan tsunami 2011 video
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tsumami
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Bay Bridge 1989
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Kobe, Japan
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Alaskan school, Good Friday 1964
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Olympia Washington, 1949
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Bird’s eye view of tents among rubble in Tangshan
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Pakistan 2005
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What to do in a earthquake? Protect yourself from falling debris –Under tables –Duck and cover DO NOT –Light fire (gas leaks?) –Go to basement!
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