Between 1992 and 2007, nine magnitude 7 or larger earthquakes have rocked the subduction zone of southern Peru and northern Chile, including a magnitude 8.1 earthquake in August 2007 near Pisco, Peru.
Pritchard and Fielding combine data from seismometers and interferometric synthetic aperture radar (InSAR) to determine the Pisco earthquake's heterogeneous slip distribution.
The analysis includes some of the first data from the Japanese Advanced Land Observation Satellite (ALOS) and the European Envisat wide-swath beam. The seismic data indicate that the slip maximum occurred 60Æ seconds after the main shock started, and the InSAR data constrain the main slip patch to be about 70 kilometers (43 miles)from the earthquake's origin.
Combined, these factors suggest an extremely low rupture velocity or a long slip rise time. Historic data indicate that no large earthquake has occurred near Pisco since at least 1746.
Though the Pisco earthquake was large, its expected magnitude would have been larger if all stress accumulated since the eighteenth century had been released.
Thus, stress from subduction was likely released through aseismic deformation within this region.
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