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What are earthquakes?

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What are earthquakes? Words to know Earthquake Focus Epicenter Seismic Wave Facts Most earthquakes occur along faults (where two plates touch) when ... – PowerPoint PPT presentation

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Title: What are earthquakes?


1
What are earthquakes?
2
Words to know
  • Earthquake
  • Focus
  • Epicenter
  • Seismic Wave

a vibration of the earth (affects large area)
the point where the earthquake starts
the point on the earths surface directly above
the focus
energy sent out from an earthquake
3
Facts
  • Most earthquakes occur along faults (where two
    plates touch) when potential energy is changed to
    kinetic energy.
  • There are more than 3,000,000 earthquakes every
    year.
  • 8,000 a day 1 every 11 seconds (According to
    the United States Geological Survey)
  • Most of these are NOT felt by humans.

4
Earthquakes to know
  • 1906 San Francisco
  • 60 times more energy than the 89 quake
  • 1989 San Francisco (Loma Prieta)

5
Notes
  • There are 2 types of Seismic Waves
  • 1.) Body Waves
  • Primary Waves (p-waves)
  • Faster
  • Travel through solid and liquid rock
  • Travels as a longitudinal wave
  • Secondary Waves (s-waves)
  • Slower
  • Travel through solid rock (not outer core)
  • Travels as a transverse wave

travel through earths body (interior)
6
Notes
  • 2.) Surface waves
  • usually responsible for shaking the ground
  • Sideways Wave
  • Shakes the ground from side to side like a snake
  • Up-and-Down Wave
  • Can open and close cracks in the earth

travel through the earths surface (crust)
7
How are earthquakes detected?
8
Words to know
  • Seismograph
  • Seismogram

a device that is used to measure earthquakes
the paper with the zigzag lines (created by a
seismograph)
9
How are earthquakes measured?
10
Notes
  • There are 2 scales used to measure earthquakes
  • 1.) Richter Scale
  • very accurate because it uses a seismograph to
    measure the ground motion
  • tells magnitude of earthquake on a scale from 1
    10 (10 is largest magnitude)
  • 2.) Mercalli Scale
  • inaccurate because scale is based on eye
    witnessed destruction from earthquake
  • scale in roman numerals from I XII
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