HR: 0800h
AN: T21A-0357    [Abstracts]
TI: Non-Volcanic Tremor Near Parkfield, CA Systematically Excited by Teleseismic Waves
AU: * Peng, Z
EM: zpeng@gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30338, United States
AU: Vidale, J E
EM: john.vidale@gmail.com
AF: Department of Earth and Space Science, University of Washington, Box 351310, Seattle, WA 98195, United States
AU: Rubinstein, J L
EM: justin@ess.washington.edu
AF: Department of Earth and Space Science, University of Washington, Box 351310, Seattle, WA 98195, United States
AU: Gomberg, J
EM: gomberg@usgs.gov
AF: US Geological Survey, Box 351310, Seattle, WA 98195, United States
AB: Non-volcanic tremor triggered by teleseismic waves was discovered recently along the subduction zones in Japan and Cascadia, and along the transform plate boundary in CA. Here we summarize non-volcanic tremor along the San Andreas fault (SAF) near Parkfield, CA triggered by the surface waves of regional and teleseismic events. We analyze 10 M ≥ 8.0 earthquakes since 2001, the M6.7 Nenana Mountain and M7.9 Denali, Alaska earthquakes in 2002 and the 2005 M7.2 Mendocino, California earthquake. We identify triggered tremor as bursts of high-frequency (~ 3-15 Hz), non-impulsive seismic energy that is coherent among many stations, and has a significant component in phase with the passing of the surface waves. We qualitatively judge the clarity of tremor observations and find the strongest, most coherent examples for the M7.9 Denali, M8.3 Hokkaido, M9.1 Sumatra, and M8.1 Kuril Islands earthquakes. The M6.7 Nenana Mountain earthquake did not trigger visible tremor, and the evidence for triggered tremor for the remaining 8 events is equivocal. The identification of tremor does not correlate strongly with peak ground velocity, but may correlate with cumulative energy density for long- period (≥ 30 s) surface waves. The observations suggest that longer-period waves may be a more effective trigger, most likely due to a better penetration to depth where tremors occur. Our observation, in concert with those of Gomberg et al., Vidale et al., and Rubinstein et al. [this meeting], suggests that non-volcanic tremor triggered by teleseismic waves is much more widespread than previously thought, and the effective stress, or the frictional coefficient is very low at depth along the SAF near Parkfield.
DE: 7205 Continental crust (1219)
DE: 7209 Earthquake dynamics (1242)
DE: 7215 Earthquake source observations (1240)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7250 Transform faults
SC: Tectonophysics [T]
MN: 2007 Fall Meeting