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Variation of seismic source parameters and stress drops within a descending slab and its implications in plate mechanics

Chung, Wai-Ying and Kanamori, Hiroo (1980) Variation of seismic source parameters and stress drops within a descending slab and its implications in plate mechanics. Physics of the Earth and Planetary Interiors, 23 (2). pp. 134-159. ISSN 0031-9201. doi:10.1016/0031-9201(80)90008-4. https://resolver.caltech.edu/CaltechAUTHORS:20141217-080309620

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Abstract

A least-squares searching technique has been developed to estimate the source dimensions of intermediate and deep focus earthquakes using azimuthal variations of body wave pulse-widths. With this method and also amplitude data, modes of rupture propagation, seismic moments, and stress drops of 17 intermediate and deep focus earthquakes in the Tonga-Kermadec region have been determined in order to investigate variations in source properties and the state of stress within the descending slab there. Three different modes of rupture; unilateral, bilateral, and circular faults, are compared and tested against observations. Results indicate that the unilateral fault is the best model for most of the earthquakes studied. Stress drops of the 17 events vary within a very large range, from 20 bar to about 4.6 kbar, and change significantly with depth. The magnitude of stress drops for depths between 220 and 430 km is very much higher than at shallower depths. This change in stress drop magnitude at about 220 km-depth seems to reflect a change in material properties both in the mantle and within the slab. Two regions of high stress drop are observed at depths of about 360 and 640 km. A relative minimum of stress drop is found at about 450–560 km where the earthquake frequency is particularly high. Earthquakes at the northern end to the Tonga arc, where the Benioff zone is laterally bent, show systematically higher stress drops than other events at comparable depths, but away from the bend. Also, events in regions of low seismicity appear to have higher stress drops than those in regions of high seismicity. The upper bound of seismic efficiency is found to decrease with depth, implying an increase of frictional force with depth at the earthquake source.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/0031-9201(80)90008-4 DOIArticle
http://www.sciencedirect.com/science/article/pii/0031920180900084PublisherArticle
ORCID:
AuthorORCID
Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 1980 Elsevier Scientific Publishing Company. Received August 28, 1979; accepted for publication November 12, 1979. We would like to thank Don Anderson, Bernard Minster, Tom Ahrens, Sean Solomon, Nafi Toksoz, and Keiiti. Aki for helpful discussions. Karen McNally and John Ci par who critically reviewed the manuscript and made suggestions for improvement are also appreciated. The research work of this paper was done at Caltech under the support of the Division of Earth Sciences, National Science Foundation, NSF Grant EAR 76-14262. The typing and final writing was done at the Department of Earth and Planetary Sciences at M.I.T. under the support of the Advanced Research Project Agency, Contract F4462075-C-0064 which was monitored by the Air Force Office of Scientific Research.
Funders:
Funding AgencyGrant Number
NSFEAR 76-14262
Air Force Office of Scientific Research (AFOSR)F4462075-C-0064
Advanced Research Projects Agency (ARPA)UNSPECIFIED
Issue or Number:2
DOI:10.1016/0031-9201(80)90008-4
Record Number:CaltechAUTHORS:20141217-080309620
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20141217-080309620
Official Citation:Wai-Ying Chung, Hiroo Kanamori, Variation of seismic source parameters and stress drops within a descending slab and its implications in plate mechanics, Physics of the Earth and Planetary Interiors, Volume 23, Issue 2, August 1980, Pages 134-159, ISSN 0031-9201, http://dx.doi.org/10.1016/0031-9201(80)90008-4. (http://www.sciencedirect.com/science/article/pii/0031920180900084)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52932
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:17 Dec 2014 17:06
Last Modified:10 Nov 2021 19:45

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