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Volcanic Earthquakes

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>From Bruce Bolt's book titled "Earthquakes" describes a magnitude 7.2 event
in 1975 on the Big Island that produced more than $4 million in damage. It
triggered a tsunami and was later followed by eruptions at Kilauea. These
particular events were caused by fault movement where the fault appeared to
trigger the subsequent tsunami and volcanic activity. No doubt, near source
effects can be produced by such events.

The minor, more harmonic seismic activity that Rick Ranous refered to can
also occur in the vicinity of volcanoes as the magma moves below the
surface. These events are used to track changes in magma movement in
attempts at monitoring volcanoes for impending eruptions. Recorded
seismicity can increase and become shallower prior to eruptions. Moderate
damage from such events are typical as experienced in Mammoth/Long Valley
Caldera region of California since the 70's. These recent events have tended
to be too small in magnitude to generate recorded near source effects.
Perhaps Mo Huang over at SMIP can help confirm this.

Fred Turner, Staff Structural Engineer, California Seismic Safety
Commission, 1900 K St. #100, Sacramento, CA 95814 916-327-1606 Work Phone,
916-322-9476 Fax fturner(--nospam--at)quiknet.com


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