| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Earth
Sciences
University of Southern California
3651 University
Avenue
Science Hall 117
Los Angeles, California 90089
We have developed procedures for inverting broadband waveforms for the
finite-moment tensors (FMTs) of regional earthquakes. The
FMT is defined in terms of second-order polynomial moments of the
source space–time function; it removes the fault-plane ambiguity of the
centroid moment tensor (CMT) and yields several additional parameters
of seismological interest: the characteristic length Lc,
width Wc, and duration Tc of the
faulting, as well as the directivity vector vd of the
fault slip. Following
McGuire et al.
(2001), we represent the observed waveform relative to the synthetic
in terms of two frequency-dependent differential times, a phase delay
p(
) and an amplitude-reduction
time q(), which we measure using
the generalized seismological data functional (GSDF) method
(Gee and Jordan,
1992). We numerically calculate the FMT partial
derivatives, which allows us to use synthetics computed by using any
forward-modeling tools. We have tested our methodology on Southern California
Seismic Network (SCSN) recordings of the 03 September 2002 Yorba
Linda earthquake (MW 4.3). Using 1D synthetic Green’s
functions, we determined the CMT and resolved fault-plane ambiguity.
To resolve the details of source finiteness, we employed a joint-inversion
technique that recovers the CMT parameters of the aftershocks and the
CMT and FMT parameters of the mainshock. The joint system
of equations relating the data to the source parameters of the
mainshock–aftershock cluster is denuisanced for path anomalies in both
observables; this projection operation effectively corrects the mainshock data
for path-related anomalies in a way similar to, but more flexible than,
empirical Green’s function (EGF) techniques. Our results
indicate that the Yorba Linda rupture occurred as left-lateral slip on a
fault-patch conjugate to the nearby, right-lateral Whittier fault. We obtained
source dimensions of Lc = 0.7 ± 0.1 km,
Wc = 0.4 ± 0.1 km, and Tc
= 0.2 ± 0.05 sec, implying a stress drop of about 3.2 MPa, and we
found a directivity of 0.8 ± 0.2, oriented up and to the northeast. The
inferred fault plane is consistent with the mainshock–aftershock
distribution relocated by Hauksson et al. (2002).
This article has been cited by other articles:
|
|
 |
|
  J. Boatwright The Persistence of Directivity in Small Earthquakes Bulletin of the Seismological Society of America, December 1, 2007; 97(6): 1850 - 1861. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Chen, L. Zhao, and T. H. Jordan Full 3D Tomography for the Crustal Structure of the Los Angeles Region Bulletin of the Seismological Society of America, August 1, 2007; 97(4): 1094 - 1120. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Tan and D. Helmberger A New Method for Determining Small Earthquake Source Parameters Using Short-Period P Waves Bulletin of the Seismological Society of America, August 1, 2007; 97(4): 1176 - 1195. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Zhao, P. Chen, and T. H. Jordan Strain Green's Tensors, Reciprocity, and Their Applications to Seismic Source and Structure Studies Bulletin of the Seismological Society of America, October 1, 2006; 96(5): 1753 - 1763. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Zhao, T. H. Jordan, K. B. Olsen, and P. Chen Frechet Kernels for Imaging Regional Earth Structure Based on Three-Dimensional Reference Models Bulletin of the Seismological Society of America, December 1, 2005; 95(6): 2066 - 2080. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
