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Presentation at AGU fall meeting 2008
Where: Moscone Center North (Hall D), San Francisco, CA
Date: Wednesday, 17th December 2008
Time: 1: 40 pm to 6: 00 pm
Paper Number: U33A-0047
Click to read the official news release
issued by the University of Washington on this study.
Abstract:
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Complex Non-volcanic Tremor Near San Andreas Fault Around Parkfield Triggered by the Great 2004 Sumatra Earthquake
Abhijit Ghosh1, John E Vidale1, Zhigang Peng2, Kenneth C Creager1, and Heidi Houston1
1Department of Earth and Space Sciences, University of Washington, Seattle, WA, 98195
2School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332
In several instances, the passing surface waves from large earthquakes have ignited non-volcanic tremor (NVT) on major faults.
Still, the mechanism of tremor and its reaction to the dynamic stressing from different body and surface waves is poorly understood.
We examine tremor around Parkfield, California near the San Andreas Fault triggered by the Mw 9.2 2004 Sumatra earthquake.
The prolonged shaking reveals the richest, and the most varied observations of dynamically-triggered tremor to date.
The tremor appears in at least three distinct locations and shows activity pulsing with encouraging stress, as has been observed in other cases.
The greatest amount of triggering and tremor modulation accompanies the long-period Love waves. Also, at times, the tremor stops before
the surface waves are complete, at other times it is still quivering after the waves have passed. While tremor is found to be sensitive
to small stress changes, there are times when stresses of comparable magnitudes do not trigger noticeable tremor. Some tremors in this
NVT sequence appear to be associated with the passage of P waves, which is unusual and surprizing given the small stresses
they impart.
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Seismograms showing teleseismic waves from Sumatra and associated tremor near Parkfield
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Map of stations, triggered and background tremor
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Last updated by Abhijit Ghosh on May 12th, 2009
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