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Earthquakes

Earthquakes. Earthquakes Result from Stress What is an Earthquake? Definition : Shaking of a crust by a release of energy Results : 1. Explosions, fires, broken sewage lines and water mains. Unstable roads, railroads, runways. 2. Tsunamis. Tsunami:.

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Earthquakes

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  1. Earthquakes

  2. Earthquakes Result from Stress • What is an Earthquake? • Definition : • Shaking of a crust by a release of energy • Results : • 1. Explosions, fires, broken sewage lines and water mains. Unstable roads, railroads, runways. • 2. Tsunamis

  3. Tsunami: Giant ocean wave generated by an earthquake whose epicenter is on the ocean floor. (computer generated photo)

  4. Causes of Earthquakes • Elastic – rebound theory • Definition : • When stress overcomes friction, sudden movement occurs and a snap forward occurs. • This is followed by a rebound or snap back.

  5. Terminology • Focus : • Where earthquakes actually occur below the surface • Epicenter : • Point on earth’s surface directly above focus

  6. Magnitude vs. Intensity • Magnitude • Definition: • The amount of energy released by an earthquake. • Intensity • Definition: • The amount of damage caused by an earthquake. • Intensity: Mercalli ScaleMagnitude: Richter Scale -Scale 1- 12 -Scale 1- 10 1= no damage 30 times more energy as you 12= total destructiongo up the scale

  7. Earthquake Waves • Kinds of wave motions • P Waves • Primary (compressional) waves • Can travel through any materials (solid, liquid, gas) • Back and forth waves • Twice as fast as S waves • S Waves • Secondary waves • Side to side waves • Can travel through solids only • L Waves • Surface waves • Slowest moving waves • Cause the most damage

  8. Seismograph:Instrument used to detect and record vibrations from earthquakes.

  9. Seismogram: Record of an event from seismograph

  10. Lag Time: Since P waves travel faster than S waves, scientists determine distance to the epicenter by analyzing the difference in arrival times.

  11. Lag Time: • The longer the lag time between the arrival of the P-waves and the arrival of the S-waves, the farther away the earthquake occurred.

  12. Locating the epicenter Triangulate between 3 or more seismograph stations Where the circles Intersect = an epicenter

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