Abstract

MONSALVO, Guillermo et al. Deformación sísmica reciente de la sierra de Pie de palo, provincia de San Juan. Rev. Asoc. Geol. Argent. [online]. 2014, vol.71, n.2, pp.260-266. ISSN 0004-4822.

In this paper we study the seismic activity in the Sierra de Pie de Palo during January 2008 to December 2009 using data recorded by 52 seismic stations from the SIEMBRA and ESP experiments. In this paper 149 crustal earthquakes were located with local magnitudes between 0.8 <M <3.7 and depths down to 40 km. The results indicate that the seismicity is mainly distributed in the Sierra de Pie de Palo with a gap in the central western part of the range and the Tulum Valley. There is a different seismic pattern for the crust located to the north and that one to the south of the range: in the northern block, 52 hypocenters have occurred at middle to lower crust levels while in the southern block, 73 earthquakes are mainly concentrated at intermediate crustal levels. There is a good correlation between the seismicity with the local crust model proposed by Perarnau et al. (2010), observing most of the seismic activity located at middle-to-lower crustal levels. The absence of seismic activity in the lowermost part of crust suggests a more ductile behavior. We constrain 128 focal mechanisms using P-wave first motions which mainly indicate reverse type solutions and secondly reverse with strike-slip components in their solutions; this agrees well with a crustal shortening in an approximate east-west direction. In addition, this seismic source study suggests a different behavior for the basement blocks whose movements and associated deformation are different, both in terms of epicentral clustering as well as in crustal depth seismic levels.

Keywords : Crustal earthquakes; Andean retroarc; Decollements; Focal mechanism; Basement blocks.

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