Grade 8 faults and earthquakes
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  • Usually associated with faulting or breaking of rocksContinuing adjustment of position results in aftershocks
  • Area in which the rocks break and move is called a faultVibrations produced is called an earthquake
  • Miners put their lamps on the hanging wall and walk on the foot wall.
  • Review earth layers
  • are the first waves to arrive at a seismograph station. P = push-pull
  • Why?
  • S-Waves- arrive after the primary waves at the seismograph station. S = shear
  • Review earth layers
  • Lord Rayleigh
  • AEH Love
  • Japanese word meaning “harbor wave”
  • Not every fault movement beneath the sea will produce a tsunami. Those faults that move in a horizontal direction or sideways will not result in a tsunami. The fault has to move in the vertical sense. In the activity, a sudden upward push triggered the wave.
  • Wave length, 500 to 600 km in ocean


  • 1. Earthquake Locations
  • 2. Earthquakes • The shaking or trembling caused by the sudden release of energy • (also known as a quake, tremor or temblor)
  • 3. Pacific Ring of Fire • 80% of all earthquakes occur in the circum-Pacific belt • more than 150,000 quakes strong enough to be felt are recorded each year
  • 4. Causes of Earthquakes ?
  • 5. Faults A break in the Earth’s crust and along the break, significant movement has taken place.
  • 6. What causes faults? Applied stresses can cause rocks to bend and stretch Eventually rocks will break away from one another
  • 7. What causes faults? • Area in which the rocks break and move is called a fault. • Vibrations produced is called an earthquake
  • 8. Elastic Rebound Theory Rocks bend until the strength of the rock is exceeded
  • 9. Elastic Rebound Theory Rupture occurs and the rocks quickly rebound to an undeformed shape.
  • 10. Elastic Rebound Theory Energy is released in waves that radiate outward from the fault. Energy Energy
  • 11. Types of Faults The direction of movement along the fault plane determines the fault type.
  • 12. Foot wall versus Hanging Wall
  • 13. Types of Faults
  • 14. Types of Faults Normal Fault • The hanging wall moves down relative to the foot wall. • This fault type is caused by tensional stress.
  • 15. Normal Fault
  • 16. Normal Fault
  • 17. Normal Fault
  • 18. Types of Faults Reverse Fault • The hanging wall moves up relative to the foot wall. • This fault is caused by compressional stress.
  • 19. Reverse Fault
  • 20. Reverse Fault
  • 21. Reverse Fault
  • 22. Types of Faults Strike-Slip • The fault exists between two pieces of crust and the • Movement occurs horizontally where the sides slide past each other.
  • 23. Strike-Slip Fault
  • 24. Strike Slip Fault
  • 25. Strike-Slip Fault
  • 26. Recap • Where do earthquakes frequently occur? • What causes earthquakes? • What causes faults? • What theory is behind the movement of rocks? • What are the three types of faults?
  • 27. Normal Fault
  • 28. Reverse Fault
  • 29. Fault Movement = Earthquake
  • 30. Slippage along fault initiates seismic waves in all directions radiating from a point. Energy
  • 31. Seismic waves are vibrations that travel through the Earth carrying the energy released during earthquakes. Energy
  • 32. Focus- where the slip happens below ground
  • 33. Epicenter-where the shaking is first felt above ground directly above the focus.
  • 34. Seismic Waves in the Earth
  • 35. Types of Seismic Waves • Body Waves –Primary Waves –Secondary Waves • Surface Waves –Love Waves –Rayleigh Waves
  • 36. Body Waves Can travel through Earth’s inner layers. (core, mantle, crust)
  • 37. Body Waves – P-waves • fastest form of wave, sometimes called compression waves. • Can move through both liquids and solids. • These waves cause rock particles to move back and forth in the same direction as the wave is traveling (push-pull).
  • 38. P-waves Path
  • 39. Body Waves – S-waves • Can travel through solids only. • Cause particles to move back and forth at right angles to the line of wave movement
  • 40. Refraction Occurs
  • 41. Surface Waves Can only travel through the surface layers (crust).
  • 42. Surface Waves – Rayleigh waves • Surface wave causing the ground to shake in an elliptical motion • Because of its motion, it moves the ground up and down, and side-to-side in the same direction that the wave is moving • Most of earthquake shaking is due to this type of wave.
  • 43. Surface Waves – Love waves • produce entirely horizontal motion • moves the ground side-to-side
  • 44.
  • 45. Earthquake Prediction / Measurement Magnitude vs. Intensity
  • 46. Magnitude vs. Intensity • Magnitude - the amount of energy released during an earthquake. • Intensity - how strong the earthquake feels to observer.
  • 47. Intensity Depends On: • Distance to Quake • Geology • Type of Building • Observer! Varies from Place to Place • Mercalli Scale- I to XII • PEIS (Phivolcs Earthquake Intensity Scale)
  • 48. Magnitude - Determined from Seismic Records Richter Scale: • Related to Energy Release • Exponential • No Upper or Lower Bounds • Largest Quakes about Mag. 8.7
  • 49. Magnitude and Energy 5. Magnitude and Intensity Magnitude Energy Explosive Power Example 9 U.S. Energy Use for a month Alaska 1964 Indonesia 2004 8 U.S. Energy Use for a day San Francisco, 1906 7 One Megaton World Series Earthquake, 1989 6 U.S. Energy Use for a minute Large Thunderstorm 5 One Kiloton 4 3 One ton of explosives World Trade Center Collapse
  • 50. Magnitude and Energy 5. Magnitude and Intensity Magnitude Energy Explosive Power Example 3 One ton of Explosives World Trade Center Collapse 2 1 Topple 50-meter tree One kilogram of explosives Head-on colision at 60 mph 0 Drop a car 10 meters Half stick of dynamite Very bad day skydiving -1 Impact of bullet One gram of explosives -2 Hammer blow -3 Dribbling a basketball
  • 51. Tsunamis A sea wave that can cause catastrophic damage when it hits a coastline.
  • 52. Causes of Tsunamis • Undersea earthquake • Undersea landslide • Eruption of undersea volcanoes • Force of asteroid crashing into the ocean
  • 53. Undersea Earthquake
  • 54. Which causes tsunamis?
  • 55. Before the Tsunami
  • 56. After the Tsunami
  • 57. Earthquake Safety
  • 58. Family Readiness •Create a family Earthquake plan •Know the safe spot in each room •Know the danger spots
  • 59. Family Readiness •Decide where your family will reunite if separated •Keep a list of emergency phone numbers •Develop a survival kit for work, car, and home
  • 60. Home Preparedness •Learn how to shut off gas, water, and electricity •Check chimneys, roofs, and wall foundations for stability •Secure heavy furnishings
  • 61. Home Preparedness •Keep heavy objects on lower shelves •Maintain emergency food, water, medici ne, first aid kit, tools, and clothing
  • 62. Emergency Supplies •First Aid supplies oBand-Aids oantibiotic ointment olatex gloves ocold/hot packs oace bandages oarm sling oTylenol or Advil odiarrhea medication
  • 63. Emergency Supplies •Equipment owork gloves oShovel oTents osleeping bags oready to eat food oClothing oradio, flashlights oCASH
  • 64. Emergency Food •Camp or backpacking stove propane tank •Canned foods manual can opener •Granola bars •Energy bars
  • 65. Safe Drinking Water • Store a supply of water o1 and 5 gallon containers odo not store on concrete • Purifying tap water o8 drops bleach per gal of water oadd bleach when storing oor, boil for 10 minutes
  • 66. Safe Drinking Water •Other sources otoilet storage tank omelted ice cubes owater trapped in pipes
  • 67. During an Earthquake •Stay away from windows, bookcases, file cabinets, heavy mirrors, and other heavy objects that could fall •Duck under a desk or sturdy table
  • 68. During an Earthquake •Watch for falling plaster or ceiling tiles •Stay undercover until the shaking stops, and hold onto your cover •If the desk or table you are under moves… move with it
  • 69. During an Earthquake •If in your car, stop, but not on a bridge, or under trees or a power line
  • 70. During an Earthquake •If outside, stay outside, and move to an area clear of overhead trees, power lines, or objects that could fall from a structure •Don’t forget about aftershocks
  • 71. After The Earthquake • Be prepared for aftershocks, plan for cover when they occur • Check for injuries, give first aid as necessary • Remain calm, try to reassure others
  • 72. After The Earthquake • Wear shoes to avoid injury from broken glass • Check for fire and take appropriate actions • Check gas, water, and electric lines • Tune to emergency broadcast system on radio