1EARTHQUAKESEvidence of Plate Tectonics Youtube PBS Broadcast of Indonesia Disasters: start at 18 sec.Dynamo that creates magnetic fieldhttp://www.nasa.gov/vision/earth/lookingatearth/29dec_magneticfield.htmlMagnetic Reversals in volcanic stratigraphyMagnetic Reversal Age ScaleMagnetic Anomalieson sea floor2Lava Magnetized in Normal FieldLava Magnetized in reversed fieldLater Lava Magnetized in Normal FieldSea floor spreading documented by magnetic reversalsMagne-tometer SurveyAge of Sea Floorhttp://earth.geol.ksu.edu/sgao/g100/plots/0829_04_age_of_ocean_floor.jpg3Velocities of Plates Lithospheric PlatesEarthquake Locations• http://earth.geol.ksu.edu/sgao/g100/plots/0916_global_seismicity.jpgFocus, epicenter, faultEarthquakesLocations and DepthsJapan Trench earthquakes4Before deformation StrainRelease of strain After strain releasedOffset Fence Nearly 3 meters Near Point Reyes North of San Francisco Occurred during 1906 Earthquakehttp://digital-desert.com/san-andreas-fault/san-andreas-05.htmlOrange grove offset, So Cal5San Andreas Fault in Southern CaliforniaSan Andreas Fault SystemSeismograph P-wavesPrimary: Pressure Wave Push-pull motion Parallel to direction of wave energy movement (propagation) Go through all types of materials Sound waves are pressure waves Primary seismic waves are pressure wavesS-waves6Secondary: Shear WaveSide to side motionSide to side motion Can only go through solid materials Secondary seismic waves Slower than primary wavesEarthquake: seismic wavesP-waves S-wavesSurface wavesSummary of seismic waves7Seismogram showing seismic wavesSeismic wave travel time curvesDifference of P and S wave travel timeMercalli scale8Intensity Measured by damage Depends on distancedistance type of materialWorld Series Earthquake apartment buildingSeattle, WA Feb 28, 2001, Nisqually quake rocked the Central Puget Sound region 6.2 Richter Magnitude 6.8 Moment magnitude Centered 57.5 km south-southwest of Seattle and 52.4 km deephttp://128.205.131.100:591/archives/Seattle.htmlhttp://www.scec.org/earthquakes/1906 San Francisco fireEarthquake magnitudes and expected worldwide occurrenceRichter magnitude determined by seismic wave recording on a
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