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Source Estimation of Finite Faults from Broadband Regional Networks

Song, Xi J. and Helmberger, Donald V. (1996) Source Estimation of Finite Faults from Broadband Regional Networks. Bulletin of the Seismological Society of America, 86 (3). pp. 797-804. ISSN 0037-1106.

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Fast estimation of point-source parameters for earthquakes has progressed much in recent years due to the development of broadband seismic networks. The expansion of these networks now provides the opportunity to investigate second-order effects such as source finiteness for regional and local events on a routine basis. This potential motivates the development of methods to quickly generate synthetic seismograms for finite sources. This is possible when the fault dimension is small compared to the source-receiver distance and when the structure around the source region is relatively simple. To study the directivity for a finite source, we discretize the fault region into a set of elements represented as point sources. We then generate the generalized rays for the best-fitting point-source location and derive for each separate ray the response for neighboring point sources using power series expansions. The response for a finite fault is then a summation over rays and elements. If we sum over elements first, we obtain an effective far-field source-time function for each ray, which is sensitive to the direction of rupture. These far-field source-time functions are convolved with the corresponding rays, and the results are summed to form the total response. A simple application of the above method is demonstrated with the tangential motions observed from the 1991 Sierra Madre earthquake. For this event, we constrain the fault dimension to be about 3 km with rupture toward the west, which is compatible with other more detailed studies.

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Additional Information:© 1996 Seismological Society of America. Manuscript received 16 December 1994. We thank Craig Scrivner, Jennifer Scott, and Laura Jones for their reviews of the manuscript. Chuck Ammon and Jeroen Ritsema provided critical reviews along with very helpful suggestions. This research was supported by the Department of Defense and was monitored by the Air Force, Office of Scientific Research, under Contract F49620-93-1-0221, and by SCEC No. 645080 as funded by NSF 8920136. Contribution No. 5480, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California.
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Department of DefenseUNSPECIFIED
Air Force Office of Scientific Research (AFOSR)F49620-93-1-0221
Southern California Earthquake Center (SCEC)645080
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Caltech Division of Geological and Planetary Sciences 5480
Issue or Number:3
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Official Citation: Xi J. Song and Donald V. Helmberger Source estimation of finite faults from broadband regional networks Bulletin of the Seismological Society of America June 1996 86:797-804
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35709
Deposited By: Ruth Sustaita
Deposited On:28 Nov 2012 19:15
Last Modified:03 Oct 2019 04:30

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