Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

The AFS. The AFS is the main structural feature of the northern Chile forearc extending between 20°S and 30°S. It originated as a left-lateral trench-parallel fault system during the Early Cretaceous (Scheuber & Andriessen, 1990). The AFS affects Mesozoic plutonic and volcanic rocks (Figure 1A). On the Mejillones Peninsula, the AFS contacts Palaeozoic metamorphic rocks with Cenozoic marine deposits and in the Coastal Cordillera Mesozoic magmatic rocks are tectonically juxtaposed with Cenozoic alluvial gravels (Cortes et al., 2007). The major branches of the AFS strongly control the topography (Figure 1), forming 300 m in high mountain fronts which are delineated by east-facing fault scarps in Pliocene-Pleistocene alluvial deposits. The kinematics of the youngest displacements of the AFS are controversial, and the surface ruptures have been interpreted as a result of left-lateral motion (Armijo and Thiele, 1990) and generated by normal faulting (Deluois et al. 1996). We observed Fig. 1: A) Major structural features in the surroundings of Antofagasta. Sites 1, 2 and 3 indicate the locations of the SCF- 1, NGF-1 and NGF-2 palaeoseismological trenches, respectively. The swath trace of the profile in B shows topography. CBF = Caleta Bandurrias Fault, RF = Rinconada Fault, CHF = Caleta Herradura Fault, MF = Mejillones Fault, AF = Aeropuerto Fault, NF = Naguayán Fault, ViF = ViF = Vinchuca Fault, FF = Fortuna Fault, BF = Bolacos Fault, VF = Viruca Fault, OF = Ordóñez Fault, SMF = Sierra Miranda Fault, SCF = Salar del Carmen Fault.