HR: 1340h
AN: S53B-1263 [Abstracts]
TI: The Anisotropic Fractured Rock in Vicinity of the San Jacinto Fault Zone, Southern California From S-Coda Waves
AU: * Martynov, V
EM: vladik@epicenter.ucsd.edu
AF: Institute of Geophysics and Planetary Physics University of California, San Diego, MS 0225,
La Jolla, CA 92093-0225, United States
AU: Vernon, F
EM: vernon@ucsd.edu
AF: Institute of Geophysics and Planetary Physics University of California, San Diego, MS 0225,
La Jolla, CA 92093-0225, United States
AU: Kilb, D
EM: dkilb@ucsd.edu
AF: Institute of Geophysics and Planetary Physics University of California, San Diego, MS 0225,
La Jolla, CA 92093-0225, United States
AU: Astiz, L
EM: lastiz@ucsd.edu
AF: Institute of Geophysics and Planetary Physics University of California, San Diego, MS 0225,
La Jolla, CA 92093-0225, United States
AB:
Recently ( AGU Full Meeting 2004, 2005 ) we discussed the influence of seismic scattering in anisotropic rock on
the S-coda waves attenuation, coda quality factor Qc and intensity of back scattering energy,
Cc. Now we improve our method of anisotropy study based on coda waves of 102 3-components records
from 11 local earthquakes, ml = 4.0 - 5.0 of 10 ANZA stations.
Examining different parts of coda
envelope ( 1. 16 sec - 41 sec, 2. 22 sec - 58 sec ) we found two types of crustal anisotropy.
1. The
S-coda waves polarized in a plane with the strike 126° and dip 72° has the smallest attenuation,
or maximum value of Qc. The largest attenuation has polarization direction that is consistent with a
vector normal to that plane. The coefficient of anisotropy equals 14.2 %. We suggest this type of anisotropy is
controlled by the San Jacinto Fault Zone.
2.A plane with the largest values of Qc has the strike ~
26° and dip varies from 51° to 79°. Coefficient of anisotropy varies from 3.9 % to 9.3 %. On our
suggestion there is a tectonic stress induced anisotropy in vicinity of the Fault Zone.
The azimuthal variations of
Qc and Cc are best fit with an anisotropic term A × cos ( 2 Az + φ ).
DE: 5144 Wave attenuation
DE: 7203 Body waves
DE: 7205 Continental crust (1219)
SC: Seismology [S]
MN: 2007 Fall Meeting