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Geodetic displacements and aftershocks following the 2001 M_w = 8.4 Peru earthquake: Implications for the mechanics of the earthquake cycle along subduction zones

Perfettini, H. and Avouac, J.-P. and Ruegg, J.-C. (2005) Geodetic displacements and aftershocks following the 2001 M_w = 8.4 Peru earthquake: Implications for the mechanics of the earthquake cycle along subduction zones. Journal of Geophysical Research B, 110 (B9). Art. No. B09404. ISSN 0148-0227.

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We analyzed aftershocks and postseismic deformation recorded by the continuous GPS station AREQ following the M_w = 8.4, 23 June 2001 Peru earthquake. This station moved by 50 cm trenchward, in a N235°E direction during the coseismic phase, and continued to move in the same direction for an additional 15 cm over the next 2 years. We compare observations with the prediction of a simple one-dimensional (1-D) system of springs, sliders, and dashpot loaded by a constant force, meant to simulate stress transfer during the seismic cycle. The model incorporates a seismogenic fault zone, obeying rate-weakening friction, a zone of deep afterslip, the brittle creep fault zone (BCFZ) obeying rate-strengthening friction, and a zone of viscous flow at depth, the ductile fault zone (DFZ). This simple model captures the main features of the temporal evolution of seismicity and deformation. Our results imply that crustal strain associated with stress accumulation during the interseismic period is probably not stationary over most of the interseismic period. The BCFZ appears to control the early postseismic response (afterslip and aftershocks), although an immediate increase, by a factor of about 1.77, of ductile shear rate is required, placing constraints on the effective viscosity of the DFZ. Following a large subduction earthquake, displacement of inland sites is trenchward in the early phase of the seismic cycle and reverse to landward after a time t i for which an analytical expression is given. This study adds support to the view that the decay rate of aftershocks may be controlled by reloading due to deep afterslip. Given the ratio of preseismic to postseismic viscous creep, we deduce that frictional stresses along the subduction interface account for probably 70% of the force transmitted along the plate interface.

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Additional Information:© 2005 American Geophysical Union. Received 4 November 2004; revised 6 May 2005; accepted 2 June 2005; published 3 September 2005. M. Olcay, J. Campos, and J.-B. de Chabalier played a crucial role in this project by making the acquisition of continuous GPS data at station UAPF possible. We are grateful to Stéphane Mazzotti and Yehuda Bock for their thoughtful reviews and comments which helped to improve the manuscript. We thank T. Melbourne and F. Webb for providing us the time series of Melbourne and Webb [2002]. Discussions with H. Tavera, L. Audin, S. Bonvalot, D. Rémy, G. Hérail, and M. Chlieh have been helpful in the redaction of the manuscript. Figure 1 has been made using GMT of P. Wessel and W. H. F. Smith. Caltech Tectonic Observatory contribution 12.
Group:Caltech Tectonics Observatory, Seismological Laboratory
Subject Keywords:2001 south Peru earthquake; postseismic relaxation; afterslip; aftershocks
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Caltech Tectonics Observatory12
Record Number:CaltechAUTHORS:20101118-073601530
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Official Citation:Perfettini, H., J.-P. Avouac, and J.-C. Ruegg (2005), Geodetic displacements and aftershocks following the 2001 Mw = 8.4 Peru earthquake: Implications for the mechanics of the earthquake cycle along subduction zones, J. Geophys. Res., 110, B09404, doi:10.1029/2004JB003522
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20871
Deposited By: Tony Diaz
Deposited On:18 Nov 2010 21:48
Last Modified:11 Jun 2015 13:57

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