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Earthquakes

Explore the formation of earthquakes, the elastic rebound theory, and the types of earthquake waves. Learn how to measure earthquakes, locate epicenters, and understand the damage caused by liquefaction. Stay informed about current seismic events and tsunamis.

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Earthquakes

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  1. Earthquakes I-880, Oakland, CA (October 1989)

  2. Magnitude 5+ earthquakes 1980 - 1990

  3. Earthquake Formation • Earthquakes occur when rock’s under stress shift along a fault.

  4. Elastic rebound theory states that rocks under stress will strain and then “rebound” back after plates slide past each other. (this causes earthquake and possibly tsunami’s)

  5. Earthquake focus and epicenter • Focus: area where fault slip occurred. • Epicenter: point on earth’s surface above focus.

  6. Finish Earth’s Deadliest Earthquakes

  7. Earthquake Basics • What is an Earthquake? • Causes of Earthquakes • Elastic Rebound Theory • How are earthquakes measured? • Seismometers/Seismographs

  8. Types of Earthquake Waves • P (primary) waves • Compressional (push-pull) • Fastest waves (first to arrive at seismograph) • Move through all materials

  9. Evidence of P-wave motion

  10. Types of Earthquake Waves • S (secondary) waves • Move perpendicular to P wave • Second fastest waves (next to arrive at seismograph) • Move ONLY through solids

  11. Types of Earthquake Waves • Surface waves • Rolling motion • Slowest waves (arrive last at seismograph) • Cause most damage

  12. Seismometer

  13. A seismogram records wave amplitude vs. time

  14. Locating an Epicenter • View Seismograms • Measure P and S wave arrivals

  15. P S

  16. Locating an Epicenter • View Seismograms • Measure P and S wave arrivals • Measure S-wave “lag” time ( = S - P) • Use Travel-Time graph to correlate distance.

  17. Locating an Epicenter • View Seismograms • Measure P and S wave arrivals • Measure S-wave “lag” time ( = S - P) • Use Travel-Time graph to correlate distance. • Triangulate Distances

  18. PRACTICE TIME!!

  19. Seismogram

  20. http://seismo.berkeley.edu/seismo/faq/iup/eq_local.html

  21. Shadow Zone • P-waves reflect between 0-104 • P-waves refract between 104-150 • S-waves only reflect • Proves outer core is LIQUID!

  22. Measuring Strength • Earthquake Magnitude • Charles Richter designed first scale • Based on height of the largest seismic wave • Every 1 increase in magnitude = 10x increase in strength

  23. Earthquake Damage: Liquifaction

  24. Earthquake Damage: Liquifaction

  25. Earthquake Damage: Liquifaction

  26. Tsunami Formation

  27. Tsunami travel time (hours; simulation) NOAA

  28. Dec. 2004 Sumatra Tsunami http://staff.aist.go.jp/kenji.satake/animation.gif

  29. Current Seismic Events • Earthquakes http://earthquake.usgs.gov/recenteqs/ • Tsunami http://wcatwc.arh.noaa.gov/tsunami.htm

  30. References Used • http://science.howstuffworks.com/earthquake6.htm • http://www.data.scec.org/chrono_index/bigbear.html • http://pubs.usgs.gov/dds/dds-29/web_pages/los_gatos.html • http://earthquake.usgs.gov/bytopic/photos.html • http://earthquake.usgs.gov/4teachers/ • http://earthquake.usgs.gov/recenteqs/

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