HR: 17:15h
AN: S12G-06    [PDF]
TI: Detection of Seismic Stress-Drop Anomalies in the Mendocino Transform Using Coda-Derived Source Spectra
AU: * Wurman, G
EM: gwurman@seismo.berkeley.edu
AF: Seismological Laboratory, University of California at Berkeley, 215 McCone Hall, Berkeley, CA 94720 United States
AU: Mayeda, K
EM: kmayeda@llnl.gov
AF: Lawrence Livermore National Laboratory, Ground-Based Nuclear Explosion Monitoring Group University of California, Livermore, CA 94551 United States
AU: Dreger, D S
EM: dreger@seismo.berkeley.edu
AF: Seismological Laboratory, University of California at Berkeley, 215 McCone Hall, Berkeley, CA 94720 United States
AB: The amplitude and decay rate of $L_{g}$ or $S_{n}$ phase coda waves can be measured over a range of narrow frequency bands to determine reliable source moment-rate spectra ({\it Mayeda and Walter,} JGR 1996). These spectra can be used to measure seismic moment and S-wave energy radiation using data from a single station. This information can in turn be used to calculate Orowan stress drop and investigate $E_{s}/M_{0}$ scaling. Events along the Mendocino transform show considerable variation in static stress drop, which is apparent in large magnitude differentials ($M_{w} - M_{L}$ as much as 1 order). Events with such large differentials exhibit enriched low frequencies as observed by examination of displacement seismograms and fourier amplitude spectra. Moment-rate spectra from the coda method confirm the anomalous properties of these events. In this study we discuss seismicity in the Mendocino transform region as observed using the coda method, in terms of static stress drop and $E_{s}/M_{0}$ scaling. We investigate possible explanations for the anomalous seismicity.
DE: 7203 Body wave propagation
DE: 7205 Continental crust (1242)
DE: 7260 Theory and modeling
DE: 7294 Instruments and techniques
SC: Seismology [S]
MN: 2003 Fall Meeting