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EARTHQUAKES

EARTHQUAKES. Chapter 19.2. Global Distribution of Earthquakes. Pacific Distribution of Volcanoes. Plate Tectonics. USGS Earthquake Hazards Program. Lisa Wald USGS Pasadena. U.S. Department of the Interior U.S. Geological Survey. Why do earthquakes happen?.

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EARTHQUAKES

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  1. EARTHQUAKES Chapter 19.2

  2. Global Distribution of Earthquakes

  3. Pacific Distribution of Volcanoes

  4. Plate Tectonics USGS Earthquake Hazards Program Lisa Wald USGS Pasadena U.S. Department of the Interior U.S. Geological Survey

  5. Why do earthquakes happen? • Rocks experience stress at locations called “faults.” • Rocks release this stress by rubbing together. • Since rocks are not smooth, this causes vibrations. • Seismic waves are caused by these vibrations. • Remember, waves are a form of energy.

  6. Three Types of Faults Strike-Slip Thrust Normal

  7. Strike-slip Fault Example

  8. Strike-slip Fault Example 1906 San Francisco Earthquake

  9. Normal Fault Example Dixie Valley-Fairview Peaks, Nevada earthquake December 16, 1954

  10. Thrust Fault Example

  11. Thrust Fault Example

  12. Are all seismic waves the same? • Primary Waves (P waves) • Longitudinal, travel the fastest • Secondary Waves (S waves) • Transverse, slower than P waves P and S waves travel in all directions from the focus. • Surface Waves • Move only on the surface • Wave motion is circular • These cause the most damage

  13. Seismic Waves

  14. Where does the earthquake occur? • Focus • The exact location where the rocks rub together inside the Earth. • Epicenter • The point on the surface directly above the focus.

  15. Seismology • Define: the study of earthquakes • It’s possible to study the Earth’s interior by analyzing seismographs • What does this compare to?

  16. Earthquake Location

  17. How strong can earthquakes get? • Richter scale • Measures the relative magnitude of an earthquake • Compared to a 2.0 eq… • 3.0 = 30x energy • 4.0 = 900x • 5.0 = 27,000x • 6.0 = 810,000x • Modified Mercalli scale • Measures the intensity of an earthquake • Takes into account the effect on a particular area

  18. Earthquake Effects - Ground Shaking Northridge, CA 1994

  19. Earthquake Effects -Ground Shaking Northridge, CA 1994

  20. Earthquake Effects - Ground Shaking Loma Prieta, CA 1989 KGO-TV News ABC-7

  21. Earthquake Effects - Ground Shaking Kobe, Japan 1995

  22. Earthquake Effects - Ground Shaking Kobe, Japan 1995

  23. Earthquake Effects - Surface Faulting Landers, CA 1992

  24. Earthquake Effects - Liquefaction Source: National Geophysical Data Center Niigata, Japan 1964

  25. Earthquake Effects - Landslides Source: National Geophysical Data Center Turnnagin Heights,Alaska,1964

  26. Earthquake Effects - Fires Loma Prieta, CA 1989 KGO-TV News ABC-7

  27. Earthquake Effects - Tsunamis 1957 Aleutian Tsunami Photograph Credit: Henry Helbush. Source: National Geophysical Data Center

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