A Rediscussion and Interpretation of Geodynamic Data Collected in the Last Decade in Northern Chile in View of the Recent Seismic Activity in Antofagasta

Abstract

The recent earthquake in Antofagasta (July 30, 1995; M = 7.6) led to a revival of the interpretation of geodynamic data in the northern part of Chile. It reconfirmed the assumption of the geophysicists at Santiago that the main earthquake-prone activity exists in the coastal Cordilleras in spite of active geodynamic processes in the Western Cordillera. Our gravimetric results of repeated observations over more than a decade (1985–1995) reconfirm exactly this assumption if it is presumed that the area around Santiago is quiet in spite of the two nearby earthquakes (Dec. 85/Jan. 86) in Valparaiso and Mendoza (Argentina). Further gravity measurements planned for 1997, adding to the still scarce repeat GPS-results in that area, are outlined which will focus on the area between Iquique and Arica besides some new reference measurements around Santiago, Puerto Montt, Antofagasta etc. The northern part of Chile, particularly the area Iquique-Arica, is still interpreted as a seismic gap area.