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Northridge aftershocks, a source study with TERRAscope data

Song, Xi J. and Helmberger, Donald V. (1997) Northridge aftershocks, a source study with TERRAscope data. Bulletin of the Seismological Society of America, 87 (4). pp. 1024-1034. ISSN 0037-1106.

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Broadband and long-period displacement waveforms from a selection of Northridge aftershocks recorded by the TERRAscope array are modeled to study source characteristics. Source mechanisms and moments are determined with long-period data using an algorithm developed by Zhao and Helmberger (1994). These results are compared with those by Hauksson et al. (1995) and Thio and Kanamori (1996). The width of the direct pulses at the nearest stations PAS and CALB are measured as indications of the source duration. Another measurement of the source-time functions of these earthquakes is obtained by comparing the short-period to long-period energy ratio in the data to that in the synthetics. These measurements are used to estimate the relative stress drop using a formula given by Cohn et al. (1982). The depth distribution of the relative stress drops indicates that the largest stress drops are in the depth range of 5 to 15 km for an aftershock population of 24 events. A correlation of extended surface wave train with source depth is demonstrated for paths crossing the San Fernando basin.

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Additional Information:© 1997 by the Seismological Society of America. Manuscript received 3 October 1996. We thank the Data Center of the Southern California Earthquake Center for making the Northridge data set available. Katrin Hafner helped us in retrieving these data. Craig Scrivner, Andy Michael, Jeroen Ritsema, and Lind Gee provided critical reviews along with very helpful suggestions. This research was supported by SCEC under Contract Number 569933, as funded by NSF Number 89-20136 and USGS Number 1434-93-G-2322. Contribution Number 5653, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California.
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Southern California Earthquake Center (SCEC)569933
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Caltech Division of Geological and Planetary Sciences5653
Issue or Number:4
Record Number:CaltechAUTHORS:20121212-080639791
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35929
Deposited By: Tony Diaz
Deposited On:12 Dec 2012 22:25
Last Modified:03 Oct 2019 04:33

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