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Seismicity and stress-drop in the eastern Transverse ranges, Southern California

Jones, Laura E. and Helmberger, Donald V. (1996) Seismicity and stress-drop in the eastern Transverse ranges, Southern California. Geophysical Research Letters, 23 (3). pp. 233-236. ISSN 0094-8276. doi:10.1029/96GL00012.

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Stress‐drops for small to moderately sized earthquakes in Southern California are found to vary systematically with source‐depth and location (tectonic environment). We determine high‐quality fault‐plane solutions, plus depth and source duration, for 17 significant (M >3.9) aftershocks associated with the June 28, 1992 Big Bear sequence, including the more recent April 4, 1994 19:04 GMT M_w 4.6 Lake Arrowhead aftershock, and a M_w 4.2 Banning Pass event which occurred on May 31, 1993 at 08:55 GMT. Given source durations and moments obtained from long‐period source estimations, and assuming a circular fault model, we estimate stress‐drop for each event. Big Bear aftershocks are moderate to high (>100 bars) stress‐drop. Events deeper than 12 km are generally high stress‐drop (>100 bars), while shallower events exhibit moderate to high stress‐drops. These results are compared with a similar analysis of Landers aftershocks in the Mojave block. For the Big Bear region, stress drops appear to correlate with depth, with the deepest events yielding the highest stress‐drops. In general, events in this region yield higher stress‐drops than events occuring in the Mojave block and those associated with the Landers and Joshua Tree sequences. Comparisons of M_L to M_O are consistent with the stress‐drop results: deep, high stress‐drop events show elevated M_L to M_O ratios.

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Additional Information:© 1996 American Geophysical Union. Received July 24, 1995; accepted September 7, 1995. This research was supported by USGS grant 1434-94-G2322. Contribution number 5573, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125.
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Caltech Division of Geological and Planetary Sciences5573
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Official Citation:Jones, L. E. and D. V. Helmberger (1996), Seismicity and stress‐drop in the Eastern Transverse Ranges, southern California, Geophys. Res. Lett., 23(3), 233–236, doi:10.1029/96GL00012.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
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Deposited On:28 Nov 2012 18:28
Last Modified:09 Nov 2021 23:17

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