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ringwoodite
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More complicated waves, too
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Real life example

• At 232450.6 GMT, on Nov. 22 2001, an earthquake
  occurred in Fiji (southwest Pacific)
• The P wave from this earthquake was recorded in
  Pasadena, CA at 233650.7 GMT
• Therefore the observed travel time is 720.10 s
• The distance between the Fiji earthquake and the
  seismometer in Pasadena is 78.8o (8762 km).
• The theoretical (expected) travel time for a P
  wave at this distance is 721.25 s.
• Therefore the travel time residual is -1.15
  seconds

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Seismic stations from Fiji to the Tonga trench
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Time residuals from Fiji across the Tonga trench
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Inferred structure in one slice across the Tonga
trench
Fiji
Tonga
Pacific plate
earthquakes
? slower P waves faster P waves ?
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I
Map of inferred structure 25 km down
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140 km down
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Earthquakes used to do global tomography and
where the seismic stations are
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A few random tomographic slices
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Comparison of different tomographic
reconstructions