HR: 1340h
AN: S13B-1306    [Abstracts]
TI: Dynamic triggering of high-frequency bursts by strong motions during the 2004 Parkfield earthquake sequence
AU: * Fischer, A D
EM: adfische@usc.edu
AF: University of Southern California, 3651 University Ave SCI 117, Los Angeles, CA 90089,
AU: Peng, Z
EM: zpeng3@mail.gatech.edu
AF: Georgia Institute of Technology, Georgia Institute of Technology, Atlanta, GA 30332,
AU: Sammis, C G
EM: sammis@usc.edu
AF: University of Southern California, 3651 University Ave SCI 117, Los Angeles, CA 90089,
AB: High-pass filtering (30Hz) of acceleration records from the USGS Parkfield Dense Seismograph Array (UPSAR) reveals a series of bursts that occur only during the strong shaking of the 2004 M6 Parkfield earthquake (Mw 6.0) and its large aftershocks. These high-frequency bursts are probably associated with events occurring very near each station, and are dynamically triggered by the strong ground motions of large earthquakes. Supporting evidence includes a lack of correlation for bursts at closely spaced stations, and a sharp decrease of array coherency with increasing frequency and inter-station distance. Lack of correlation may be associated with the extremely high attenuation in the highly fractured layer that compromises the top few hundred meters of crust. The threshold stress required for triggering was found to be 0.16 to 6.5 MPa with a high signal-to-noise ratio, consistent with a previous estimate based on strong motion data from the 1999 Chi-Chi earthquake in Taiwan [Fischer et al., 2007, in review].
DE: 7200 SEISMOLOGY
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2007 Fall Meeting