Chapter 2 Forces in Earth

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Chapter 2Forces in Earth

• Section 2-2
• Shake and Quake

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I. Seismic Wave

• Types of Waves
• Compression Wave
• Caused by matter being squeezed and stretched

http//web.ics.purdue.edu/braile/edumod/waves/Pwa
ve.gif
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• Transverse Wave
• Matter moves in right angles to the direction the
  wave is moving.

http//www.tjhsst.edu/jlafever/wanimate/bshear.gi
f
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• Seismic Wave
• Wave generated by earthquakes

http//www.uwgb.edu/dutchs/GRAPHIC0/Animations/Sei
sWaveAnim.gif
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B. Focus

• Point in the earths interior where seismic waves
  start
• Can be between 5km and 700km below the surface
• Seismic waves travel outward through the earth in
  all directions from the focus

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http//t3.pacific.edu/teams/M031606/focus_epicente
r.jpg
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C. Seismograph

• An instrument used to detect waves
• Can detect waves from as far as the other side of
  the earth

http//www.tcem.org/Kinemetrics_seismograph.jpg
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D. Primary and Secondary Waves

• Originate from the focus and travel through the
  earths interior
• Underground waves

http//physics.fortlewis.edu/Astronomy/astronomy2
0today/CHAISSON/AT307/IMAGES/AT07FG13.JPG
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E. Epicenter

• The point on the earths surface directly above
  the focus.

http//upload.wikimedia.org/wikipedia/commons/9/9b
/Epicenter.png
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F. Surface Wave

• Formed when seismic waves reach the epicenter
• Travel out from the epicenter
• Are slower than primary and secondary waves
• Cause the most damage

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http//www.dkimages.com/discover/previews/792/5103
706.JPG
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II. Visualizing Waves

• Primary Waves
• Cause alternating compression and stretching in
  the direction of the wave
• Cause back and forth, rocking movements on
  Earths surface
• Also known as P-Waves or Compression Waves

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http//web.ics.purdue.edu/braile/edumod/waves/Pwa
ve.gif
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B. Secondary Waves

• Cause rock to vibrate at right angles to the
  direction of the wave.
• Causes side to side movements on Earths surface.
• Also known as S-Waves or Transverse Waves.

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http//www.tjhsst.edu/jlafever/wanimate/bshear.gi
f
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C. Surface Waves

• One type of surface wave causes side to side
  rocking motion

http//images.google.com/imgres?imgurlhttp//met.
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• Another type of surface wave causes up-down and
  rolling motions.

http//images.google.com/imgres?imgurlhttp//met.
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lhttp//met.gov.pk/Subpage4/waves.htmlusg__hZpn
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