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The Sumatra subduction zone: A case for a locked fault zone extending into the mantle

Simoes, Martine and Avouac, Jean Philippe and Cattin, Rodolphe and Henry, Pierre (2004) The Sumatra subduction zone: A case for a locked fault zone extending into the mantle. Journal of Geophysical Research B, 109 (B10). Art. No. B10402 . ISSN 0148-0227. http://resolver.caltech.edu/CaltechAUTHORS:20101118-135335005

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Abstract

A current view is that the portion of the subduction interface that remains locked in the time interval between large interplate earthquakes, hereinafter referred to as the locked fault zone (LFZ), does not extend into the mantle because serpentinization of the mantle wedge would favor stable aseismic sliding. Here, we test this view in the case of the Sumatra subduction zone where the downdip end of the LFZ can be well constrained from the pattern and rate of uplift deduced from coral growth and from GPS measurements of horizontal deformation. These geodetic data are modeled from a creeping dislocation embedded in an elastic half-space and indicate that the LFZ extends 132 ± 10/7 km from the trench, to a depth between 35 and 57 km. By combining this information with the geometry of the plate interface as constrained from two-dimensional gravimetric modeling and seismicity, we show that the LFZ extends below the forearc Moho, which is estimated to lie at a depth of ~30 km, at a horizontal distance of 110 km from the trench. So, in this particular island arc setting, the LFZ most probably extends into the mantle, implying that either the mantle is not serpentinized, or that the presence of serpentine does not necessarily imply stable sliding. From thermal modeling, the temperature at the downdip end of the LFZ is estimated to be 260 ± 100°C. This temperature seems too low for thermally activated ductile flow, so that aseismic slip is most probably due to pressure and/or temperature induced steady state brittle sliding, possibly favored by fluids released from the subducting slab.


Item Type:Article
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http://dx.doi.org/10.1029/2003JB002958 DOIUNSPECIFIED
http://www.agu.org/pubs/crossref/2004/2003JB002958.shtmlPublisherUNSPECIFIED
Additional Information:© 2004 American Geophysical Union. Received 23 December 2003; revised 28 June 2004; accepted 26 July 2004; published 2 October 2004. We wish to thank K. Sieh and D. Natawidjaja, from the California Institute of Technology (Pasadena, California) for fruitful discussions on the coral data as well as for corrections on the manuscript. We also wish to thank N. Chamot-Rooke from the Ecole Normale Superieure (Paris, France) for his interest in the results of this study, and H. Hebert from Laboratoire de Detection et de Geophysique (CEA, France) for very useful discussions on the marine geophysics data. This manuscript was also substantially improved thanks to comments and suggestions by J. Freymueller, M. Reyners, and the anonymous Associate Editor.
Group:Caltech Tectonics Observatory, Caltech Tectonics Observatory. Sumatran Plate Boundary
Subject Keywords:locked fault zone; interseismic deformation; Sumatra
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Caltech Tectonics Observatory10
Record Number:CaltechAUTHORS:20101118-135335005
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20101118-135335005
Official Citation:Simoes, M., J. P. Avouac, R. Cattin, and P. Henry (2004), The Sumatra subduction zone: A case for a locked fault zone extending into the mantle, J. Geophys. Res., 109, B10402, doi:10.1029/2003JB002958
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20901
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:18 Nov 2010 22:00
Last Modified:26 Dec 2012 12:39

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