Earthquakes

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Earthquakes

• - The movement of the ground, caused by waves of
  energy released as rocks move along faults
• Fault a large fracture in rocks, from several
  meters to many kilometers long, where rocks not
  only crack but also move along either side of the
  break
• Types of Stresses tension, compression, shear
• Types of Faults Normal, Reverse,
  Strike-Slip

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1. Normal Fault a pull apart fracture in rocks,
where rocks that are above the fault surface drop
downward in relation to rocks that are below the
fault surface
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2. Reverse Fault a compression fracture in
rocks, where rocks that are above the fault
surface are forced up over rocks that are below
the fault surface
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3. Strike-Slip Fault a break in rocks where
rocks on either side of the fault move past each
other, instead of above or below each other
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Concept of hanging wall and footwall
Headwall Rock surface ABOVE the fault
Footwall Rock surface ABOVE the fault
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Earthquakes (cont.)
Slow steady pressure produces folds Types of
folds anticlines - upward bulging fold (ant
hill) syncline - downward bulging fold
(dip) monocline - rock layers on one side of a
fold are higher than the other side
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Anticline
Syncline
Monocline
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Stresses Building Mountains

• Folded Mountains caused by compression
• Fault-Block Mountains caused by tension
• Plutonic Mountains result from vertical force
  created by rising magma
• Volcanic Mountains result of magma from
  convergent boundaries reaching Earths surface

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Folded Mountains
Fault-Block Mountains
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Plutonic Mountain Half Dome
Volcanic Mountain Mt. Fuji
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Earthquake Evidence

• Creep very slow down-slope movement, 1cm/yr.,
  leads to severe cracks in buildings
• Slide rapid down-slope movement of soil, rocks
  debris
• Scarps cliff created by sudden earth movements
  along a fault, identified by a curved scar in the
  landscape
• Fissure a long crack in soil or rock, up to
  many kilometers in length
• Tsunami an ocean wave caused by earthquakes,
  may reach over 100ft. In height

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Scarp
Creep
Landslide
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Fissure
Tsunami created by 9.0 earthquake on Dec.26, 2004
off the west coast of Sumatra in the Indian Ocean
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• Chile Quake
• Feb. 27, 2010
• Magnitude 8.8 Offshore Maule, Chile
• Resultant ?
• Tsunami

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Earthquake Damage

• Depends on
• 1. location of earthquake
• 2. type of ground under buildings
• 3. building design materials
• 4. closeness to coastline in case of tsunami

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The End
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Extra Credit

• Find and read a news article on Earthquakes -
  write a three paragraph essay about the article
  (at least-5 sentences per paragraph). Please
  include the article.
• Sneak it to me no later than the day of the
  Earthquake test for credit