| The 23-June-2001 8.4-Mw magnitude earthquake partially filled the
1868-seismic-gap in southern Perú. This earthquake produced a thrust
faulting dislocation with a rupture that started at about ~200 km SE
from the 1996's Nazca earthquake epicenter, and stopped near Ilo, at about
300 km from the epicenter, near a positive gravity anomaly offshore Ilo. The
23-June-2001-earthquake dislocation zone is under the Arequipa sedimentary
Basin. Pre- and post-seismic GPS measurements at Camaná and Ilo at
SIRGAS-GPS points (SIRGAS: Sistema de Referencia Geocéntrico para América
del Sur) and the average sea level pre- and post-seismic event at Mollendo
tide gauge provide evidence of a regional subsidence of southern Perú, with
84 cm at Camaná, 16 cm at Ilo, and 15 cm at Mollendo. Field surveys post
earthquake document significant subsidence in Camaná resort beaches.
Results of a simple dislocation modelling of 23-June-2001 earthquake agree
reasonably well with the observed data. However, the coseismic subsidence of
southern Perú is at variance with the regional uplift of southern Perú
based on Neotectonic studies. This fact, suggests that, in recent geological
times, the magnitude of the secular uplift due to tectonic plate converge has
been larger than the coseismic deformation recovery. |