The Pisco (Peru) earthquake of 15 August 2007

Abstract

The seismic activity in Peru has its origin in the convergence process between the Nazca and South American plates. Such convergence takes place at an average speed on the order of 7–8 cm/year (DeMets et al. 1980; Norabuena et al. 1999). This process is responsible for the offshore earthquakes with depths smaller than 60 km that take place off the coast of Peru (Dorbath et al. 1990; Tavera and Buforn 2001), which are all associated with seismogenic contact. Moderate to large earth- quakes occur on average at a rate of more than 60 per year and usually affect the towns near their epicenters. Earthquakes of larger magnitude (Mw > 7.0) have produced significant damage over broad areas, such as the event that occurred in southern Peru on 23 June 2001 (Mw = 8.2), which affected an area of 370 × 70 km2 between the towns of Atico (Arequipa) and Ilo (Moquegua) (Tavera et al. 2006). The earthquake that is the subject of this article occurred on 15 August 2007 with a magnitude of Mw 7.9 and was named “the Pisco earthquake” because its epicenter was located 60 km west of Pisco city. The earthquake produced significant dam- age in Pisco city (approximately 80% of all structures) and minor damage in nearby towns, and it was assigned an approxi- mate intensity of VII–VIII on the Modified Mercalli Intensity (MMI) scale in Pisco city. The epicenter of the Pisco earthquake and its aftershocks were located between the rupture areas of the 1974 Lima earthquake (Mw 7.5) and the 1996 Nazca earthquake (Mw 7.7). The earthquake also produced a tsunami, which originated south of the epicenter in the Paracas Peninsula. Focal mechanisms for these earthquakes generally correspond to reverse motion with nodal planes oriented in a NNW-SSE direction and near horizontal plane dipping to the east, which corresponds to the subducting plate (Tavera and Buforn 2001).