Application of High Resolution Data Sets to Seismicity/Gravity Field Interactions on Local Scale - An Example From Northern Chile

We used the high resolution aftershock data set from the 1995, Mw 8.1 Antofagasta earthquake and a combined satellite/terrestrial data set of the gravity field in the rupture area to demonstrate the usefulness of local data in parameter correlation between seismicity and gravity field anomalies. With these data sets, we achieved first results on the proposed relation between massive batholithic structures in the overriding plate and the seismogenic part of the subduction interface in the North Chilean subduction zone. Defined areas of high co-seismic moment release on the rupture plane correlated well with pronounced positive isostatic residual anomalies (IRAs) of the gravity field. These findings resulted in a first hypothetic model where the batholithic structures lock the subduction interface during the interseismic cycle, producing increasing slip deficit with surrounding areas and foster stress concentration on suggested asperity structures.In this study we like to present new evidences for the role of batholithic structures in seismogenic processes through a new seismic b-value distribution considering earthquake catalogs from before the 1995 Antofagasta event, providing a detailed map of vertical stress anomalies in the rupture area and linking a gravity derived density model to high seismic velocities from a 3D local tomography study. Combining GPS derived moment release with co-seismic coastal uplift data over Mejillones Peninsula further helped to identify a segment boundary between the Antofagasta and the 2007, Mw 7.9 Tocopilla rupture planes.