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Seismic imaging of active faults in the Alboran Basin: Implications for earthquake and tsunami hazards in the west Mediterranean coasts

Eulàlia Gràcia, Rafael Bartolome, Claudio Lo Iacono, Ximena Moreno, Hector Perea, César R. Ranero, Sara Martinez, Eulalia Masana, Susana Diez, and Juanjo Dañobeitia

The present-day crustal deformation of the Alboran Sea is driven mainly by the NW-SE convergence (4.5-5.6 mm/yr) between the African and Eurasian plates. This convergence is accommodated over a wide deformation zone mainly distributed among extensional, compressive and large strike-slip faults with significant seismic activity SE of the Iberian Peninsula. Instrumental seismicity is characterized by continuous, shallow seismic events of low to moderate magnitude (Mw < 5.5) although, large destructive earthquakes (MSK Intensity IX-X) have also occurred in the region (e.g. 1522 Almeria, 1910 Adra, 1994 and 2004 Al-Hoceima). We will present an overview of large active faults recently characterized in the Alboran Sea. The data has been acquired during successive marine geophysical surveys carried out in the frame of national projects (IMPULS, EVENT and SHAKE) and European projects (ESF WESTMED and ESF TOPOMED-GASSIS). Fault exploration of active fault systems integrates the most advanced technologies covering different scales of resolution. Swath-bathymetry and sidescan sonar data allow identifying fault seafloor expression. Sub-seafloor seismic imaging, ranging from high-resolution sub-bottom profiler to deep-multichannel seismic data allow detecting the stratigraphic evidence of past seismic activity, and sediment cores allow knowing the age of the most recent faulted sequences. We will mainly focus to a) the southern terminations of the Eastern Betic Shear Zone at sea, such as the left-lateral Carboneras and Al-Idrissi faults; b) associated structures, such as the large dextral Yusuf fault; c) extensional features in the Adra region, example of fault growth and linkage; and d) large compressional and potentially tsunamigenic structures, such as the Alboran Ridge. Our main goal is to characterize the shallow and crustal structure of these active faults in order to evaluate their seismic potential, which may represent a significant earthquake and potential tsunami hazard for the coasts of Western Europe and North Africa.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013