Earth

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Earths internal structurea seismologists view
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Types of waves used by seismologists
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Organizing the information

• Seismic travel times
• Dispersion curves
• Free oscillation frequencies

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Putting it all together
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The crust
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Mohorovicic 1909
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The lithosphere
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The asthenosphere
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Mineralogical models of the upper 400 km

• Pyrolite (Ringwood 1975) is a garnet peridotite
  mainly of olivine and orthopyroxene
• Piclogite (Anderson and Bass 1984) is a
  clinopyroxene and garnet rich aggregate with some
  olivine

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The transition zone

• Characterized by discontinuities in velocity and
  density models.
• Observed mainly by SS and PP underside
  reflections/

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The lower mantle is relatively
simple,exceptD
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The discovery of the core

• The core Oldham 1906. Drop in velocity ? shadow
  zone in P arrivals ? liquid core
• Inner core Lehman 1936. Increase in velocity ?
  triplication ? solid inner core
• Innermost core 2003

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