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Published October 2004 | Published
Journal Article Open

Spectral-Element Moment Tensor Inversions for Earthquakes in Southern California

Abstract

We have developed and implemented an automated moment tensor inversion procedure to determine source parameters for southern California earthquakes. The method is based upon spectral-element simulations of regional seismic wave propagation in an integrated 3D southern California velocity model. Sensitivity to source parameters is determined by numerically calculating the Fréchet derivatives required for the moment tensor inversion. We minimize a waveform misfit function, and allow limited time shifts between data and corresponding synthetics to accommodate additional 3D heterogeneity not included in our model. The technique is applied to three recent southern California earthquakes: the 9 September 2001, M_L 4.2 Hollywood event, the 22 February 2003, M_L 5.4 Big Bear event, and the 14 December 2001, M_L 4.0 Diamond Bar event. Using about half of the available three-component data at periods of 6 sec and longer, we obtain focal mechanisms, depths, and moment magnitudes that are generally in good agreement with estimates based upon traditional body-wave and surface-wave inversions.

Additional Information

© 2004 Seismological Society of America. Manuscript received 26 February 2004. We thank Egill Hauksson and Ying Tan for providing first-motion and body-wave moment tensor mechanisms; Hiroo Kanomori, Egill Hauksson, Donald V. Helmberger, Gene A. Ichinose, and an anonymous reviewer for helpful comments; and SCSN for access to the data. All the map figures were produced with GMT (Wessel and Smith, 1991). This research was funded in part by the National Science Foundation under grant EAR-0309576 and the USGS NEHRP. This research was also supported by the Southern California Earthquake Center (SCEC). SCEC is funded by NSF Cooperative Agreement EAR-0106924 and USGS Cooperative Agreement 02HQAG0008. The SCEC contribution number for this paper is 772. This is contribution No. 9080 of the Division of Geological and Planetary Sciences of the California Institute of Technology.

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Created:
August 19, 2023
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October 26, 2023