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Inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 Imperial Valley, California, earthquake

Hartzell, Stephen H. and Heaton, Thomas H. (1983) Inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 Imperial Valley, California, earthquake. Bulletin of the Seismological Society of America, 73 (6). pp. 1553-1583. ISSN 0037-1106. https://resolver.caltech.edu/CaltechAUTHORS:20130228-093912445

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Abstract

A least-squares point-by-point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 Imperial Valley, California, earthquake. The Imperial fault is represented by a plane embedded in a half-space where the elastic properties vary with depth. The inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right-lateral strike-slip and normal dip-slip components of motion. Inversions are run for different fault dips and for both constant and variable rupture velocity models. Effects of different data sets are also investigated. Inversions are compared which use the strong ground motions alone, the teleseismic body waves alone, and simultaneously the strong ground motion and teleseismic records. The inversions are stabilized by adding both smoothing and positivity constraints. The moment is estimated to be 5.0 × 10^(25) dyne-cm and the fault dip 90° ± 5°. Dislocation in the hypocentral region south of the United States-Mexican border is relatively small and almost dies out near the border. Dislocation then increases sharply north of the border to a maximum of about 2 m under Interstate 8. Dipslip motion is minor compared to strike-slip motion and is concentrated in the sediments. The best-fitting constant rupture velocity is 80 per cent of the local shear-wave velocity. However, there is a suggestion that the rupture front accelerated from the hypocenter northward. The 1979 Imperial Valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border.


Item Type:Article
Related URLs:
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http://bssa.geoscienceworld.org/content/73/6A/1553.abstractPublisherArticle
ORCID:
AuthorORCID
Heaton, Thomas H.0000-0003-3363-2197
Additional Information:© 1983 Seismological Society of America. Manuscript received 17 March 1983. This research was done at the Pasadena office of the U.S. Geological Survey. We gratefully acknowledge the cooperation and support of the faculty of the Seismological Laboratory, California Institute of Technology. We also thank Allen Olson, Ronan Le Bras, Paul Spudich, Ralph Archuleta, and Carl Johnson for helpful discussion. We thank Jim Morl for his assistance in gathering teleseismic records.
Issue or Number:6
Record Number:CaltechAUTHORS:20130228-093912445
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130228-093912445
Official Citation: Stephen H. Hartzell and Thomas H. Heaton Inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 Imperial Valley, California, earthquake Bulletin of the Seismological Society of America, December 1983, v. 73, p. 1553-1583
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37191
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:28 Feb 2013 23:12
Last Modified:03 Oct 2019 04:45

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