HR: 1340h
AN: S13B-1049 [Abstracts]
TI: Searching for the difference in attenuation between
the fast and slow shear waves
AU: Gao, S S
EM: gao@ksu.edu
AF: Department of Geology, Kansas State University, Manhattan, KS 66506
United States
AU: * Liu, K H
EM: liu@ksu.edu
AF: Department of Geology, Kansas State University, Manhattan, KS 66506
United States
AU: Zhang, Z
EM: zhuzhang@ksu.edu
AF: Department of Geology, Kansas State University, Manhattan, KS 66506
United States
AU: Gao, Y
EM: gaoyuan@seis.ac.cn
AF: Institute of Earthquake Science, China Earthquake Administration, Beijing, 100036
China
AB:
Measurements of shear-wave splitting parameters
(fast polarization direction PHI and splitting time DT)
have become a powerful and routine technique to study
the deformation field of the earth's interior.
While it is evident that velocity anisotropy can lead
to significant arrival-time difference between the
fast and slow shear waves, the question of whether the two waves
have observable difference in attenuation has
rarely been addressed. In principle, such a difference
in attenuation is likely to be observed,
especially from local shear-waves recorded in areas
with fluid-filled cracks; relative to the fast wave,
the slow wave may experience higher attenuation.
Successful detection and characterization of the difference
in attenuation may provide additional constraints on
the properties of the anisotropic media.
We have developed and tested a grid-searching procedure to search
for the optimal PHI, DT, and the relative attenuation factor
(as quantified by t* which is travel-time over Q) between
the fast and slow shear waves that give rise to the maximum
cross correlation coefficient between the corrected fast and
slow waves. The procedure can be used for
both SKS/SKKS phases and shear-waves originated from local
earthquakes. Details about the procedure and its applications
on seismic data recorded at a number of locations will be presented.
DE: 7200 SEISMOLOGY
DE: 7203 Body wave propagation
DE: 7218 Lithosphere and upper mantle
SC: Seismology [S]
MN: 2004 AGU Fall Meeting