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# Chapter 11 Earthquakes

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### Transcript

• 1. Chapter 11 Earthquakes
• 2. When rocks break they move along faults.
• 3. Applied forces cause rocks to undergo elastic deformation.
• 4. When elastic limits are passed, rocks break.
• 5. Rock on one side of a fault can move up, down, or sideways in relation to rock on the other side of the fault.
• 6. Faults occur because forces inside the Earth cause earthâ€™s plates to move placing stress on or near the plate edge
• 7. Rocks will bend, compress, stretch, and possibly break.
• 8. Earthquake: vibrations produced by breaking rock
• 9. Rocks break, move along the fault, and return to original shapes.
• 10. Rock on one side of a fault can move over, under, or past each other along fault lines.
• 11. Three types of forces act on rocks: tension, compression, and shear.
• 12. Tension forces; normal fault: caused by rock above the fault moving downward in relation to the rock below the fault.
• 13.
• 14. Reverse fault: compression forces squeeze rock above the fault up and over the rock below the fault.
• 15.
• 16. Created by shear forces; strikeslip fault: rocks on either side of the fault move past each other without much upward or downward motion.
• 17.
• 18. Section 2:
• 19. Seismic â€“ waves generated by an earthquake can move the ground forward and backward, up and down, and side to side.
• 20. Focus: an earthquakeâ€™s point of energy release
• 21. Primary waves (P waves): cause particles in rocks to move back and forth in the same direction that the wave is traveling.
• 22. Secondary waves (S waves) â€“ cause particles in rock to move at right angles to the direction of wave travel.
• 23. Surface waves â€“ move rock particles in a backward, rolling motion and a sideways swaying motion.
• 24. The point on the Earthâ€™s surface directly above the earthquake focus is called the epicenter.
• 25. The different speeds of seismic waves allow scientists to determine the epicenter.
• 26. Primary waves move the fastest. Secondary waves follow Surface waves move slowest and arrive at the seismograph station last.
• 27. Seismograph: measures seismic waves.
• 28. Consists of a rotating drum of paper and a pendulum with an attached pen.
• 29. The paper record of a seismic event is called a seismogram.
• 30. Earthâ€™s structure consists of an inner, mostly iron, solid core surrounded by a mostly iron liquid outer core surrounded by the mantle.
• 31. The curst is Earthâ€™s outer layer, about 5 to 60 km thick.
• 32. A seismic waveâ€™s speed and direction change as the wave moves through different layers with various densities.
• 33. Density generally increases with depth as pressures increase.
• 34. Shadow zones do not receive seismic waves because the waves are bent or stopped by materials of different density.
• 35. Changes in seismic wave speed allowed detection of boundaries between Earthâ€™s layers.
• 36. Although earthquakes are natural geologic events, they kill many people and cause a lot of damage
• 37. Seismologists
• scientists who study earthquakes
• 38. Magnitude
• measure of energy released by an earthquake
• determined by the Richter scale and based on the height of the lines on a seismogram
• 39.
• 40. The Richter Scale has no upper limit
• 41. Most earthquakes have magnitudes too low to be felt by humans â€“ 3.0 to 4.9 on the Richter Scale
• 42. The modified Mercalli intensity scale describes earthquake intensity based on structural and geologic damage
• 43. Liquefaction
• shaking from an earthquake can make wet soil act like a liquid
• 44.
• 45. Ocean waves caused by earthquake are called tsunamis
• 46.
• caused when a sudden movement of the ocean floor pushes against the water
• can travel thousands of kilometers in all directions
• 47. Earthquakes cannot be reliably predicted
• 48.
• Knowing how and where to plan for earthquakes can help prevent death and damage
• Buildings can be constructed to withstand seismic vibrations
• 49.
• Flexible, circular moorings are being placed under buildings
• made of alternating layers of rubber and steel
• 50. The rubber acts like a cushion to absorb earthquake waves
• 51. Homes can be protected by careful placement of heavy objects and securing gas appliances
• 52. During an earthquake, crawl under a sturdy table or desk
• outdoors, stay away from buildings and power lines
• 53. After an earthquake, check for water or gas line damage leave IMMEDIATELY if a gas smell is present
• 54.
• 55.