HR: 1340h
AN: S53A-1085    [Abstracts]
TI: Analysis of earthquake source spectra from similar events in the aftershock sequences of the 1999 M7.4 Izmit and M7.1 Duzce earthquakes
AU: * Yang, W
EM: wenzheny@usc.edu
AF: Department of Earth Sciences, University of Southern California, 3651 Trousdale Parkway, Los Angeles, CA 90089-0740
AU: Peng, Z
EM: zpeng@ess.ucla.edu
AF: Department of Earth and Space Sciences, University of California at Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095
AU: Ben-Zion, Y
EM: benzion@usc.edu
AF: Department of Earth Sciences, University of Southern California, 3651 Trousdale Parkway, Los Angeles, CA 90089-0740
AB: We use an iterative stacking method (Prieto et al., 2004) to study the relative source spectra of similar earthquakes in the aftershocks of the 1999 Mw7.4 Izmit and Mw7.1 Duzce earthquake sequences. The initial study employs a tight cluster of 160 events along the Karadere segment that were recorded by 10 short-period stations. We compute the P-wave spectra using a multitaper technique, and separate the stacked source and receiver-path spectra terms iteratively from the observed spectra. The relative log potency computed from the low-frequency amplitude of the source spectra term scales with the local magnitude with a slope close to 1. An empirical Green's function (EGF) is used to correct the attenuation and derive the relative spectra shapes of events in different potency/moment bins. Synthetic calculations are used to test the validity of some of the results. The receiver-path spectra term for stations inside or close to the fault zone are found to be larger than those of other stations. This may be related to the fault-zone trapping structure and related site effects in the area discussed by Ben-Zion et al. (2003). The continuing work will focus on estimating the corner frequency, stress drop, and radiated seismic energy from the relative source spectra. The same method will be applied to other similar earthquake clusters identified by Peng and Ben-Zion (2005), and larger events (M3-5) recorded by the strong ground motion instruments. Updated results will be presented in the meeting.
UR: http://earth.usc.edu/~wenzheny
DE: 3205 Fourier analysis (3255)
SC: Seismology [S]
MN: Fall Meeting 2005