Build your own seismograph

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Build your own seismograph

• Alan Kafka, Boston College
• Michael Hubenthal, IRIS

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We didnt feel it so how do we know?
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• Seismology The study of seismic waves.
• Seismograph Instrument that records seismic
  waves.
• Seismogram The record of ground motion that is
  produced by a seismograph.

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Your Task

• design and construct a seismograph using common
  household and craft materials provided

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An excellent design will be

• made of the common inexpensive materials provided
  for this exercise
• capable of determining the relative size of each
  disturbance it measures
• capable of measuring vibrations continuously for
  at least one minute
• capable of capturing the time when these
  disturbances occurred
• capable of measuring vibrations from three
  different sources a bang on or shaking of the
  table holding the seismograph a person jumping
  up and down on the floor next to the table on
  which your seismograph is located and a ball
  bounced off of a wall or floor nearby.

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How does a seismograph work?
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To measure horizontal ground motion
A heavy mass is decoupled from the Earth by means
of a pendulum.
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When the ground moves, the mass tends to remain
stationary because of its inertia, but the
support (frame) moves with the Earth.
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The movement of the Earth relative to the
stationary mass is recorded on a rotating drum.
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To measure vertical motion The principle is the
same, but the mass is suspended on a spring.
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With a modern seismograph, the ground motion is
also recorded on a computer.
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AS1 Seismograph
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The Great Sumatra Earthquake of 2004
Seismograms Recorded at Boston College
Magnitude 9.0 December 26, 2004
Magnitude 8.7 March 28, 2005
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AS1 Seismograms
Same Distance, Different Magnitudes
Three Sumatra Earthquakes Recorded at Weston
Observatory Boston College
?133
Seismograms are shown on the same scale.
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Magnitude 6.7 Gulf of California January 4, 2006
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Same Magnitude, Different Distances
Seismograms are shown on the same scale.
El Salvador Magnitude 7.7, January 13, 2001
?33
India Magnitude 7.7, January 26, 2001
?106
AS1 Seismograms
El Salvador and India Earthquakes Recorded at
Devlin Hall Boston College
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Same Earthquake, Different Distances
Seismograms are shown on the same scale.
Phoenix Country Day School, Paradise Valley,
AZ ?7
AS1 Seismograms
Weston High School,Weston, MA ?38
Parkfield, CA Earthquake Magnitude 6.0, 09/28/04
Time (sec/102)
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