(5 12 09) How Earthquakes Work

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  • 1. Jordan Chaires P.4. 5-12-09
  • 2. How Does an Earthquake Work?  An earthquake is a vibration that travels through the earth's crust.
  • 3. Causes of Earthquakes All kinds of things can cause earthquakes: movements of the earth's plates volcanic eruptions meteor impacts underground explosions (an underground nuclear test, for example) collapsing structures (such as a collapsing mine)
  • 4. Steps to an Earthquake Destruction to Plate families, homes, Seismic Waves Movements and contries
  • 5. Facts  An Earthquake occurs about once every 11 seconds.  There have been more than 1.5 million earthquake- related fatalities in the last hundred years.
  • 6. Plate Tectonics  Seismology - the study of earthquakes  The basic theory is that the surface layer of the earth (lithosphere) is comprised of many plates that slide over the athenosphere layer.
  • 7. Collide  At the boundaries between these huge plates of soil and rock, three different things can happen:  divergent plate boundary (Plates can move apart)  convergent plate boundaries (Plates can push together)  transform boundaries (Plates slide against each other)
  • 8. Faults  Faults are formed where these plates meet  Faults are breaks in the earth's crust where the blocks of rock on each side are moving in different directions  Earthquakes are most common along fault lines
  • 9. Seismic Waves  When a sudden break or shift occurs in the earth's crust, the energy radiates out as seismic waves, just as the energy from a disturbance in a body of water radiates out in wave form.  Primary waves – can travel through solid, liquid and gas, and so will pass completely through the body of the earth. Typically arrive at the surface as an abrupt thud.  Secondary waves - don't move straight through the earth. They only travel through solid material, and so are stopped at the liquid layer in the earth's core
  • 10. Seismograph  A seismograph is a machine that registers the different waves.
  • 11. The Richter Scale The Richter Scale is used to rate the amount of energy it released. The wave amplitude increases 100 times between a level 7 earthquake and a level 9 earthquake. The largest earthquake on record registered an 9.5 on the currently used Richter Scale.
  • 12. The Richter Scale
  • 13. Conclusion  Earthquakes are mainly formed by the movements of the earth's plates.  They occur all the time but not all of them result in major destruction or fatalities  Seismographs measure earthquakes