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Interplate coupling and temporal variation of mechanisms of intermediate-depth earthquakes in Chile

Astiz, Luciana and Kanamori, Hiroo (1986) Interplate coupling and temporal variation of mechanisms of intermediate-depth earthquakes in Chile. Bulletin of the Seismological Society of America, 76 (6). pp. 1614-1622. ISSN 0037-1106. http://resolver.caltech.edu/CaltechAUTHORS:20140827-141040079

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Abstract

We investigated the temporal variation of the mechanism of large intraplate earthquakes at intermediate depths in relation to the occurrence of large under-thrusting earthquakes in Chile. Focal mechanisms were determined for three large events (1 March 1934: M = 7.1, d = 120 km; 20 April 1949: M = 7.3, d = 70 km; and 8 May 1971: M_W = 7.2, d = 150 km) which occurred down-dip of the great 1960 Chilean earthquake (M_W = 9.5) rupture zone. The 1971 event is down-dip compressional: θ (strike) = 12°, δ (dip) = 80°, and λ (rake) = 100°. The 1949 earthquake focal mechanisms is θ = 350°, δ = 70°, and λ = −130°. The data available for the 1934 event are consistent with a down-dip tensional mechanism. Thus, the two events which occurred prior to the great 1960 Chilean earthquake are down-dip tensional. Published fault plane solutions of large intermediate-depth earthquakes (28 March 1965 and 7 November 1981) which occurred down-dip of the Valparaiso earthquakes of 1971 (M_W = 7.8) and 1985 (M_W = 8.0) are also down-dip tensional. These results suggest that before a major thrust earthquake, the interplate boundary is strongly coupled, and the subducted slab is under tension at intermediate depths; after the occurrence of an interplate thrust event, the displacement on the thrust boundary induces transient compressional stress at intermediate depth in the down-going slab. This interpretation is consistent with the hypothesis that temporal variations of focal mechanisms of outer-rise events are due to changes of interplate coupling.


Item Type:Article
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http://bssa.geoscienceworld.org/content/76/6/1614.abstractPublisherArticle
Additional Information:© 1986 Seismological Society of America. Manuscript received 13 June 1986. We thank Larry Ruff for encouragement at an early stage of this project and Thorne Lay for useful discussion. Holly K. Eissler, Steve Grand, Hitoshi Kawakatsu, and Tom Heaton helped us with their critical comments on the manuscript. This research was supported by U.S. Geological Survey Grants 14-08-0001-G1170 and 14-08-0001-G1277, Contribution No. 4343, Division of Geological and Planetary Sciences, California institute of Technology, Pasadena, California.
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Funding AgencyGrant Number
USGS14-08-0001-G1170
USGS14-08-0001-G1277
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Caltech Division of Geological and Planetary Sciences4343
Record Number:CaltechAUTHORS:20140827-141040079
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140827-141040079
Official Citation:Astiz, L., & Kanamori, H. (1986). Interplate coupling and temporal variation of mechanisms of intermediate-depth earthquakes in Chile. Bulletin of the Seismological Society of America, 76(6), 1614-1622.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49003
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:27 Aug 2014 21:29
Last Modified:28 Aug 2014 22:36

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