Earthquake crisis unveils the growth of an incipient continental fault system

This article have a datasets associated "Regional centroid moment tensors for earthquakes in the 2016 South Alboran seismic crisis" http://hdl.handle.net/10261/177887

Large continental faults extend for thousands of kilometres to form boundaries between rigid tectonic blocks. These faults are associated with prominent topographic features and can produce large earthquakes. Here we show the first evidence of a major tectonic structure in its initial-stage, the Al-Idrissi Fault System (AIFS), in the Alboran Sea. Combining bathymetric and seismic reflection data, together with seismological analyses of the 2016 M-w 6.4 earthquake offshore Morocco - the largest event ever recorded in the area - we unveil a 3D geometry for the AIFS. We report evidence of left-lateral strike-slip displacement, characterise the fault segmentation and demonstrate that AIFS is the source of the 2016 events. The occurrence of the M-w 6.4 earthquake together with historical and instrumental events supports that the AIFS is currently growing through propagation and linkage of its segments. Thus, the AIFS provides a unique model of the inception and growth of a young plate boundary fault system.

This research was supported by projects CGL2011-30005-C02-02, CTM2015-70155-R and Acción IDRISSI (MINECO/FEDER), shiptime on board the R/V Sarmiento de Gamboa and R/V Angeles Alvariño, EuroFleets-2 grant agreement 312762, and access to IFREMER AUVs AsterX and IdefX (France) through Ocean Facilities Exchange Group (OFEG). We also thank the Instituto Geografico Nacional (IGN, Spain) for providing seismological data. H.P. acknowledges the EU Horizon 2020 programme under grant agreement No H2020-MSCA-IF-2014 657769. E.d’A. acknowledges the French programme Actions Marges, the LabexMER (ANR-10-LABX-19-01) and the EuroFleets grant agreement 228344.

Peer reviewed