Gracia, E. , Grevemeyer, Ingo , Perea, H. , Bartolome, R., Martinez- Loriente, S. , Gomez de la Pena, L., Ranero, Cesar, Villasenor, A. , Diez, S. , d’Acremont, E. and Rabaute, A. (2017) Unveiling the fault source of the January 25th 2016, Mw 6.4 earthquake (Alboran Sea) constrained by seismological and geological data. [Poster] In: Subduction Interface Processes SIP 2017. , 19.04-21.04.2017, Castelldefels, Barcelona, Spain .

Abstract

On the 25th January 2016 a magnitude Mw 6.3 earthquake struck 45 km offshore north
Morocco, the largest recorded event in the Alboran Sea (western Mediterranean). It
was preceded on 21 January by an earthquake of magnitude 5.1 in the same epicentral
area, and was followed by numerous aftershocks whose locations mainly migrated
south and northeast from the mainshock. The mainshock nucleated at a releasing bend
of the poorly known Al-Idrissi Fault. According to slip inversion we assume a 20 to
maximum 30 km long rupture zone. We use swath-bathymetry, seismic reflection
profiles and seismological data to characterize and document Quaternary activity on
the 100 km long Al-Idrissi Fault. We report evidence of left-lateral strike-slip
displacement, characterize their fault segments and demonstrate that Al-Idrissi is the
fault source of the 2016 earthquake events. Located along a crustal boundary that
separates the West and East Alboran Sea, the Al-Idrissi Fault is a young structure. Its
central segment, mainly transpressive, was developed during the Early Pliocene while
the north and south segments are transtensional and of Quaternary age. All these
observations together suggest that the Mw 6.4 earthquake broke across the southern
and central segment boundary. Therefore, the complete rupture of the Al-Idrissi Fault
should be considered and might generate a greater rupture (Mw 7.2), significantly
increasing the potential hazard of the structure.

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