The seismogenic structure of the Antofagasta subduction zone and future perspectives for the Iquique Local Network (ILN) in northern Chile

Material inhomogeneities or geometrical irregularities are suggested to act as seismogenic structures which can influence rupture nucleation, propagation, and termination of large earthquakes. To evidence such a behaviour, a direct link between tectonic and/or geological conditions and the areas of focused co-seismic moment release or slip on a rupture plane has to be established. In case of the Antofagasta region, we were able to identify two prominent asperity structures in the post-seismic aftershock sequence of the Mw8.0, 1995, earthquake and related them to geologic features located in the overriding crust. We looked at co-seismic moment release, aftershock radiated seismic energy, isostatic residual anomalies of the local gravity field, vp velocities and vp/vs ratios, and studied aftershock focal mechanism solutions in the vicinity of the asperity structures. All these parameters were able to support our presented model. With the installation of an International Plate Boundary Observatory in Northern Chile (IPOC) we want to apply our experiences gained in the Antofagasta region to the northern adjacent subduction zone segment. Our presentation will give an overview on the aims of the Iquique Local Network (ILN) as one component of the IPOC, whose major tasks are to monitor the seismic activity along the subduction interface and at the fault systems in the overriding crust, and the assumed transient seismic signals along proposed material boundaries. The data base should help to constrain changes in the local stress field and in material properties providing information on the seismic stage of the observed subduction zone segment.