Co-, Post- and Pre(?)-seismic Displacements Associated with the Mw 8.4 Southern Peru Earthquake of 23 June 2001 from Continuous GPS Measurements

Abstract

On 23 June 2001, at 20:33 UTC, a major earthquake occurred near the coast of southern Peru, about 190 km west of Arequipa (16.15°S, 73.40°W). A revised magnitude of 8.4 was computed for this earthquake by the United States Geological Survey, NEIC (see http://neic.usgs.gov/neis/bulletin/01_EVENTS/0l0623203313/010623203313.html for further information). The earthquake occurred along the west coast of Peru (Figure 1) at the boundary between the Nazca and South American Plates and resulted from thrust faulting along this boundary as the Nazca Plate subducts beneath the South American Plate. The two plates are converging toward each other at a rate of 78 mm/yr (DeMets et al. , 1990). Southwestern Peru has a history of very large earthquakes. The 23 June shock originated just southeast of the source of a magnitude 7.7 earthquake that occurred in November 1996. This area of the plate boundary has not recorded a major rupture since the 1868 earthquake of magnitude approximately 8.5–9 (Dorbath et al. , 1990; Comte and Pardo, 1991). The 23 June shock occurred in a previously identified seismic gap (Nishenko, 1985). The 1868 earthquake was more destructive than the 23 June earthquake and produced a tsunami that killed hundreds of people along the South American coast. The 23 June earthquake is very similar to the 1995 Mw 8.1 Antofagasta earthquake (Ruegg et al. , 1996), which ruptured a zone of about 180 × 70 km2 of the Chilean coast, along which no major historical earthquake has been recognized before. The city of Arequipa, located 190 km east of the main shock epicenter, experienced damage during the 23 June earthquake. At Arequipa several precise positioning systems are permanently operating, including continuous GPS station of the IGS, DORIS beacon, Satellite Laser Ranging. In this study we give a quick report about surface deformation …