Chlieh, Mohamed and Perfettini, Hugo and Tavera, Hernando and Avouac, Jean-Philippe and Remy, Dominique and Nocquet, Jean-Mathieu and Rolandone, Frédérique and Bondoux, Francis and Gabalda, Germinal and Bonvalot, Sylvain (2011) Interseismic coupling and seismic potential along the Central Andes subduction zone. Journal of Geophysical Research B, 116 . Art. No. B12405. ISSN 0148-0227 http://resolver.caltech.edu/CaltechAUTHORS:20120127-094423904
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We use about two decades of geodetic measurements to characterize interseismic strain build up along the Central Andes subduction zone from Lima, Peru, to Antofagasta, Chile. These measurements are modeled assuming a 3-plate model (Nazca, Andean sliver and South America Craton) and spatially varying interseismic coupling (ISC) on the Nazca megathrust interface. We also determine slip models of the 1996 M_w = 7.7 Nazca, the 2001 M_w = 8.4 Arequipa, the 2007 M_w = 8.0 Pisco and the M_w = 7.7 Tocopilla earthquakes. We find that the data require a highly heterogeneous ISC pattern and that, overall, areas with large seismic slip coincide with areas which remain locked in the interseismic period (with high ISC). Offshore Lima where the ISC is high, a M_w∼8.6–8.8 earthquake occurred in 1746. This area ruptured again in a sequence of four M_w∼8.0 earthquakes in 1940, 1966, 1974 and 2007 but these events released only a small fraction of the elastic strain which has built up since 1746 so that enough elastic strain might be available there to generate a M_w > 8.5 earthquake. The region where the Nazca ridge subducts appears to be mostly creeping aseismically in the interseismic period (low ISC) and seems to act as a permanent barrier as no large earthquake ruptured through it in the last 500 years. In southern Peru, ISC is relatively high and the deficit of moment accumulated since the M_w∼8.8 earthquake of 1868 is equivalent to a magnitude M_w∼8.4 earthquake. Two asperities separated by a subtle aseismic creeping patch are revealed there. This aseismic patch may arrest some rupture as happened during the 2001 Arequipa earthquake, but the larger earthquakes of 1604 and 1868 were able to rupture through it. In northern Chile, ISC is very high and the rupture of the 2007 Tocopilla earthquake has released only 4% of the elastic strain that has accumulated since 1877. The deficit of moment which has accumulated there is equivalent to a magnitude M_w∼8.7 earthquake. This study thus provides elements to assess the location, size and magnitude of future large megathurst earthquakes in the Central Andes subduction zone. Caveats of this study are that interseismic strain of the forearc is assumed time invariant and entirely elastic. Also a major source of uncertainty is due to fact that the available data place very little constraints on interseismic coupling at shallow depth near the trench, except offshore Lima where sea bottom geodetic measurements have been collected suggesting strong coupling.
|Additional Information:||© 2011 by the American Geophysical Union. Received 16 December 2010; revised 10 September 2011; accepted 3 October 2011; published 17 December 2011. The Institut de Recherche pour le Développement (IRD) of France supported the main funding for this research. Logistical support was provided by the Centre National d’Etudes Spatiales (CNES) through the Tosca grant, convention CNES/95532. The European Space Agency (ESA) provided the Envisat and ERS satellite images through CAT-1 project ID5487. We deeply thank J.P. Loveless, K. Wang and three anonymous reviewers for their constructive comments. M.C. deeply thanks Khadija and Souad Zakari for their supports. We used the Generic Mapping Tool (http://gmt.soest.hawaii.edu/) for Figures 1–11.|
|Official Citation:||Chlieh, M., H. Perfettini, H. Tavera, J.-P. Avouac, D. Remy, J.-M. Nocquet, F. Rolandone, F. Bondoux, G. Gabalda, and S. Bonvalot (2011), Interseismic coupling and seismic potential along the Central Andes subduction zone, J. Geophys. Res., 116, B12405, doi:10.1029/2010JB008166|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||30 Jan 2012 16:04|
|Last Modified:||26 Dec 2012 14:44|
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