Coseismic slip model of the 2007 August Pisco earthquake (Peru) as constrained by Wide Swath radar observations

Abstract

SUMMARY The Pisco earthquake (M w 8.0; 2007 August 15) occurred offshore of Peru’s southern coast at the subduction interface between the Nazca and South American plates. It ruptured a previously identified seismic gap along the Peruvian margin. We use Wide Swath InSAR observations acquired by the Envisat satellite in descending and ascending orbits to constrain coseismic slip distribution of this subduction earthquake. The data show movement of the coastal regions by as much as 85 cm in the line-of-sight of the satellite. Distributed-slip model indicates that the coseismic slip reaches values of about 5.5 m at a depth of ∼18–20 km. The slip is confined to less than 40 km depth, with most of the moment release located on the shallow parts of the interface above 30 km depth. The region with maximum coseismic slip in the InSAR model is located offshore, close to the seismic moment centroid location. The geodetic estimate of seismic moment is 1.23 × 10 21 Nm (M w 8.06), consistent with seismic estimates. The slip model inferred from the InSAR observations suggests that the Pisco earthquake ruptured only a portion of the seismic gap zone in Peru between 13.5 ◦ S and 14.5 ◦ S, hence there is still a significant seismic gap to the south of the 2007 event that has not experienced a large earthquake since at least 1687.