1Evidence of Plate Tectonics Earthquakes• Time To See Your AdvisorPlate MapAnimation link• http://www-personal.umich.edu/~vdpluijm/plates.gifhttp://www.ucmp.berkeley.edu/geology/tectonics.htmlDynamo that creates magnetic field• http://www.nasa.gov/vision/earth/lookingatearth/29dec_magneticfield.htmlMovement of Magnetic North• http://www.nasa.gov/vision/earth/lookingatearth/29dec_magneticfield.htmlMovement of Magnetic pole since 1600s• http://www.geolab.nrcan.gc.ca/geomag/long_mvt_nmp2_e.shtmlApparent Polar wandering for North America and EurasiaPole location with moving continents2Magnetic Reversals in volcanic stratigraphyMagnetic Reversal Age ScaleLava Magnetized in Normal FieldLava Magnetized in reversed fieldLater Lava Magnetized in Normal FieldSea floor spreading documented by magnetic reversalsMagne-tometerSurveyMagnetic AnomaliesAge of Sea Floor• http://earth.geol.ksu.edu/sgao/g100/plots/0829_04_age_of_ocean_floor.jpg3Earthquake Locations Japan Trench earthquakes JOIDES ResolutionAge of Emperor Seamount ChainVelocities of Plates Radio TelescopePlate movement over 200 my Wegener’s Pangaea 200 mya (early Jurassic)4150 mya (late Jurassic) 100 million years ago 90 mya (Cretaceous)50 mya (early Cenozoic) 20 mya (late Cenozoic) Present DayIn 50 million years?In 250 million years??Lithospheric Plates5Earthquake Locations• http://earth.geol.ksu.edu/sgao/g100/plots/0916_global_seismicity.jpgPressure 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 wavesPrimary Wavehttp://astro.uchicago.edu/cara/outreach/se/ysi/1999/intro2.htmlShear Wave• Transverse--Side to side motion• Can only go through solid materials• Secondary seismic waves• Slower than primary wavesSecondary Wavehttp://astro.uchicago.edu/cara/outreach/se/ysi/1999/intro2.htmlEarthquake: seismic wavesWorld 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 fire6Focus, epicenter, fault Orange grove offset, So Cal Before deformationStrain Release of strain After strain releasedSummary of elastic reboundSan Andreas Fault System Seismograph7Seismogram showing seismic wavesP-waves P-wavesS-waves S-waves S-type surface wavesOcean-type surface waves Summary of seismic wavesSeismic wave travel time curves8Difference of P and S wave travel timeMercalli scaleRichter magnitude determined by seismic wave recording on a seismogramEarthquake magnitudes and expected worldwide
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