HR: 0800h
AN: S51A-0972    [Abstracts]
TI: Nonisotropic Scattering of S-Waves in the Crust Around the San Jacinto Faulting Zone, Southern California
AU: * Martynov, V G
EM: vladik@epicenter.ucsd.edu
AF: V.G.M., Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, 0225, Scripps Institution of Oceanography, La Jolla, CA 92093 United States
AU: Vernon, F L
EM: vernon@epicenter.ucsd.edu
AF: V.G.M., Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, 0225, Scripps Institution of Oceanography, La Jolla, CA 92093 United States
AU: Kilb, D L
EM: dkilb@epicenter.ucsd.edu
AF: V.G.M., Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, 0225, Scripps Institution of Oceanography, La Jolla, CA 92093 United States
AB: We studied the energy distribution of seismic scattering based on the source factor results ( SF in the single -backscattering model of Aki and Chouet, 1975, JGR ) obtained from polarization -dependent S-coda amplitudes. We have tested our algorithm on band-passed ( 2 - 4 Hz ) waveforms of a M_L}= 5.1 local crustal earthquake ( h = 18.7 km ) recorded by the ANZA broadband network in southern California. We analyzed the records of 10 stations, of which 7 are < 20 km away. Over all stations S-coda waves with a polarization azimuth of 73° ( clockwise from North ) and vertical angle of 9° ( positive values downward ) have the maximum value of SF. We find the polarization direction of the maximum energy of backscattering S-waves is consistent with the orientation of a normal plane of the scattering patterns, strike 164° and dip 81°. This suggests the distribution of the scatterers is nonuniform. They are predominantly oriented S16°E and are responsible for the maximum value of the backscattering energy of S-waves in the crust beneath ANZA. This orientation is consistent with the axes of compression obtained from results of seismogenic deformation field ( Unruh et al., 1996, JGR ) in southern California. The scatterers ( opened cracks? ) are parallel the maximum compressional stress.
DE: 7203 Body waves
DE: 7205 Continental crust (1219)
SC: Seismology [S]
MN: Fall Meeting 2005