Preliminary Results of Crustal Structure from the LARSE-II Passive Recording Experiment Using
Teleseismic P-to-S Converted Waves
L. Zhu
Department of Earth Sciences, Univ of Southern
California Los Angeles, CA
The 1998–1999 Los Angeles Region Seismic Experiment (LARSE-II)
contained a passive recording phase in which 83 three-component
broadband and short-period instruments were deployed along a 100
km long profile. The profile started near the coast in Malibu and
traversed the Santa Monica Mts., the San Fernando and the Santa
Clarita Valleys, theWestern San Gabriel Mts., the San Andreas Fault
(SAF), and ended in the Antelope Valley of the Mojave Desert. In
this study, we use teleseismic P-to-S converted waves to image subsurface
sedimentary basins and deep crustal structures.We generated
a 2-D crustal structure image along the profile by stacking and migrating
the radial receiver functions
using
the Common Conversion
Point (CCP) stacking technique. The San Fernando Basin and the
Santa Clarita Basin are well imaged with the basin bottoming at 6 to
8 km
depth
. In addition, a low-
velocity
patch exists near the surface
under the Antelope Valley which might be an old sedimentary basin
or low-
velocity
rocks. The Moho is seen clearly as a continuous flat
feature at a
depth
of 32 km under the Mojave Desert. It is terminated
near the downward extension of the SAF. In contrast, the Moho in
the western side of SAF is quite different from the one under the
Mojave Block in terms of sharpness and continuity. We also compared
the Bouguer gravity anomaly and teleseismic arrival time delays
along the profile with the predictions from the inferred crustal
model. The preliminary modeling shows that most of the anomalies
can be explained by the model.
AAPG Search and Discovery Article #90904©2001 AAPG Pacific Section Meeting, Universal City, California