HR: 1340h
AN: S43C-1014    [Abstracts]
TI: Crustal Seismicity and Recent Faults in Southern Peru
AU: * David, C
EM: d.claire@dgf.uchile.cl
AF: University of Chile, Department of Geology, Plaza Ercilla 803, Santiago, 651-1227 Chile
AU: Comte, D
EM: dcomte@dgf.uchile.cl
AF: University of Chile, Department of Geophysics, Blanco Encalada 2002, Santiago, 651-1227 Chile
AU: Tavera, H
EM: jtavera@geo.igp.gob.pe
AF: Instituto Geofisico del Peru, Calle Calatrava 216 - Urbanizacion Camino Real, La Molina, Lima, 4361683 Peru
AU: Audin, L
EM: Laurence.Audin@ird.fr
AF: IRD, 213, rue La Fayette 75480, Paris, Cedex 10 France
AU: Herail, G
EM: gherail@paris.ird.fr
AF: IRD, 213, rue La Fayette 75480, Paris, Cedex 10 France
AB: Most seismological studies in southern Peru have been focused on the downgoing slab seismicity in order to constrain the Wadati-Benioff zone. This study deals with the intra-continental seismicity of the southern Peru forearc (17,3$\deg$S - 18,5$\deg$S) in a post-seismic context (Arequipa thrust earthquake, Mw=8.4, 23 June, 2001). It is difficult to identify historical crustal earthquake from available catalogues, however some crustal events teleseismically recorded can be found since 1976; they exhibit normal focal mechanism solutions in the southern Peru volcanic arc and inverse focal mechanism solutions in the Central Depression. Following a notable increase of shallow crustal seismicity located close to the Western Cordillera after the 23 June 2001, a temporary seismic network was deployed between January and March 2003 in order to study the Wadati-Benioff zone and monitoring the crustal seismicity in southern Peru. From the about 1700 events locally recorded by the local network, 300 crustal earthquakes were identified in the Peruvian forearc between Tacna and Moquegua. This crustal seismicity is distributed along a lineament located at depths between 0 and 60 km, dipping at about 45$\deg$ from the Western Cordillera towards the coast, almost perpendicular to the subducting slab; this behaviour was previously observed in northern Chile and in southern Peru, north of the study zone (16$\deg$S). In the Central Depression, seismic activity is not superficial occurring between 25-60 km depth and it is mostly characterized by inverse focal mechanism solutions. Superficial faults situated in the Central Depression and in the Coastal Cordillera can not be associated with the seismic activity observed in this area. However, in the Pre-Cordillera, crustal seismicity occurs at depths between 0-15 km and can be correlated with shallow fault systems recognized by satellite images and on the field. For examples, the Incapuquio fault system which was a transpressive system in Cretaceous time seems seismically active and could be associated with sinestral strike-slips. The Purgatorio fault which has been identified by a pronounced discontinuity of the topography and the presence of terraces of accumulation could be associated with pure component movements. The correlation between seismological data and geomorpho-tectonic observations on field gives new insight in the southern Peru forearc deformation.
DE: 7230 Seismicity and seismotectonics
DE: 7200 SEISMOLOGY
SC: Seismology [S]
MN: 2004 AGU Fall Meeting