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Constraints on fault and lithosphere rheology from the coseismic slip and postseismic afterslip of the 2006 M_w 7.0 Mozambique earthquake

Copley, Alex and Hollingsworth, James and Bergman, Eric (2012) Constraints on fault and lithosphere rheology from the coseismic slip and postseismic afterslip of the 2006 M_w 7.0 Mozambique earthquake. Journal of Geophysical Research B, 117 (B3). Art. No. B03404. ISSN 0148-0227. doi:10.1029/2011JB008580.

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The 2006 M_w 7.0 Mozambique (Machaze) normal-faulting earthquake ruptured an unusually steeply dipping fault plane (~75°). The amount of slip in the earthquake decreased from depths of ~10 km toward the surface, and this shallow slip deficit was at least partly recovered by postseismic afterslip on the shallow part of the fault plane. An adjacent normal fault segment slipped postseismically (and possibly also co-seismically) at shallow depths with a large strike-slip component, in response to the stresses generated by slip on the main earthquake fault plane. Our observations suggest that the fault zone behaves in a stick-slip manner in the crystalline basement, and that where it cuts the sedimentary layer the coseismic rupture was partially arrested and there was significant postseismic creep. We discuss the effects of such behavior on the large-scale tectonics of continental regions, and on the assessment of seismic hazard on similar fault systems. The steep dip of the fault suggests the re-activation of a preexisting structure with a coefficient of friction at least ~25–45% lower than that on optimally oriented planes, and analysis of the deformation following an aftershock indicates that the value of the parameter ‘a’ that describes the rate-dependence of fault friction lies in the range 1 × 10^(−3)–2 × 10^(−2). The lack of long-wavelength postseismic relaxation suggests viscosities in the ductile lithosphere of greater than ~2 × 10^(19) Pa s, and an examination of the tectonic geomorphology in the region identifies ways in which similar fault systems can be identified before they rupture in future earthquakes.

Item Type:Article
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Hollingsworth, James0000-0003-0122-296X
Additional Information:© 2012 American Geophysical Union. Received 8 June 2011; revised 13 January 2012; accepted 17 January 2012; published 10 March 2012. We thank James Jackson for help in acquiring SPOT images via ISIS/CNES. Includes material copyright CNES 2010, distribution Spot Image S.A. We thank three anonymous reviewers for helpful comments on the manuscript. We thank Pembroke College in the University of Cambridge and the Gordon and Betty Moore Foundation for financial support.
Funding AgencyGrant Number
University of Cambridge Pembroke CollegeUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:InSAR; Mozambique earthquake; afterslip; postseismic; rheology; seismology
Issue or Number:B3
Record Number:CaltechAUTHORS:20120411-110535004
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Official Citation:Copley, A., J. Hollingsworth, and E. Bergman (2012), Constraints on fault and lithosphere rheology from the coseismic slip and postseismic afterslip of the 2006 Mw7.0 Mozambique earthquake, J. Geophys. Res., 117, B03404, doi:10.1029/ 2011JB008580
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:30061
Deposited By: Tony Diaz
Deposited On:11 Apr 2012 20:19
Last Modified:09 Nov 2021 19:35

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