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Features of Earthquakes

Features of Earthquakes. Origin of Seismic Waves. Moving rocks get caught on each other at faults Stress builds up until elastic limit is passed Built-up energy is released at the focus

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Features of Earthquakes

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  1. Features of Earthquakes

  2. Origin of Seismic Waves • Moving rocks get caught on each other at faults • Stress builds up until elastic limit is passed • Built-up energy is released at the focus • Seismic waves are produced & travel outward from focus

  3. 3 types of seismic waves • Primary • Secondary • Surface

  4. Primary or P-waves • Particles in rocks move back and forth in same direction that wave is traveling • Fastest

  5. Secondary or S-waves • Particles in rocks move at right angles to direction wave is traveling • Slower

  6. Surface Waves • Particles in rocks move in a backward rolling motion & side to side swaying • Slowest • Most destructive

  7. Epicenter • Focus

  8. Locating the epicenter • Seismologists take seismograms from 3 different seismograph locations. • They use these to determine the distance to the epicenter of each station. • Then they draw a circle around each station with the distance as a radius. • Point where all 3 intersect is the epicenter.

  9. Seismograph

  10. Basic Structure of Earth • Crust • Upper mantle • Lower mantle • Outer core • Inner core

  11. Crust • Outermost layer • Thickness varies 5 -60 km • More silicon & aluminum • Less magnesium & iron • Less dense than mantle

  12. Upper Mantle • Contains the asthenosphere • Weak rock flows slowly

  13. Lower mantle • Made of silicon, oxygen, magnesium, & iron

  14. Outer Core • Liquid made mostly of iron

  15. Inner Core • Solid • Dense • Mostly iron with nickel, oxygen, silicon,& sulfur • Pressure keeps it solid

  16. Shadow Zone • area where NO seismic waves are detected • Primary are slowed and bent but not stopped • Secondary are not transmitted through the liquid outer core

  17. Moho • Boundary between crust and upper mantle (Mohorovicic discontinuity)

  18. Speed of Seismic Waves • Seismic waves speed up through bottom of crust & upper mantle • Primary and Secondary slow down in asthenosphere • Gains speed in solid part of mantle • Secondary stops in liquid outer core • Primary slow in outer core and speed up in solid inner core

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