Evidence for a seafloor rupture of the Carboneras Fault Zone (southern Spain): Relation to the 1522 Almería earthquake?

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Abstract

High-resolution sea floor imaging (narrow beam sediment profiler) yields evidence for an offshore rupture along a strand of the Carboneras Fault Zone (CFZ) in the Gulf of Almería off southern Spain. The observed faults affect the seafloor and cut the Late Holocene sedimentary cover, hence the faults are regarded as active and the escarpments as relatively fresh. Seafloor faulting is associated with escarpments, fissures, pressure ridges, folds, and reverse faults indicating sinistral strike-slip faulting with a significant vertical displacement. Adjacent to the major fault zone secondary phenomena such as submarine slumps and slides are observed. The observed fresh escarpments imply an offshore rupture during a major earthquake along the CFZ. The southern Iberian margin and the Afro-Eurasian convergence zone form an area of moderate seismicity. However, some major events occurred, such as the 1522 Almería earthquake (EMS IX; [IGN (2005) Instituto Geografico Nacional, www.ign.es]), which affected large areas in the western Mediterranean. Different epicentral areas have been suspected, mainly along the 50 km long sinistral CFZ; however, no on-shore surface ruptures and paleoseismological evidences for this event have been found. Based on our data, a new epicentral area is proposed in the Gulf of Almería precisely along the observed sea floor rupture area, where the CFZ extend at least for 100 km offshore. Our findings suggest a specific seismic hazards and tsunami potential for offshore active and seismogenic faults in the Alborán Sea.

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