Seismic crisis reveals the growth of a young fault system in the Alboran Sea

Autonomous Underwater Vehicle (AUV) IdefX (IFREMER, France). Photo: Zoraida Rosselló (Azora films).
2 Setembre 2019

An international team led by the Institut de Ciències del Mar (ICM-CSIC, Barcelona) demonstrate the growth of a young fault in the Alboran Sea, called the Al-Idrissi Fault System, source of the magnitude (Mw) 6.4 earthquake, which affected Al-Hoceima, Melilla and the south of the Iberian Peninsula in January 2016. The study, published in Nature Communications, shows the generation and growth of an active fault system.

Geologically, the Alboran Sea is a young basin located between the Eurasia and the African tectonic plates. At the boundary between both plates is located the Al-Idrissi Fault System (AIFS), across the seafloor of the Alboran Sea. It represents the longest active tectonic structure in the region. The fault is about 100 km long and 1 to 4.8 km wide, accommodating a total slip rate of 3.8 mm/yr.

Our study shows, for the first time, the detailed structure of a fault system on its initial stage. This incipient fault system is a unique opportunity to study the growth and evolution of a young strike-slip fault”, explains the ICM-CSIC researcher Eulàlia Gràcia Mont, leader of this work.


Tectonic setting and seismicity in the Alboran Sea

This Al-Idrissi Fault System links to the north with the NS Faults in the Almeria margin; and to the south with the faults of North African margin. In the middle of the system is the epicenter of the 25th January 2016, Mw 6.4 earthquake event, the largest recorded in the Alboran sea since the first seismometers were installed, more than a hundred years ago.  The occurrence of this event, named as “Al-Idrissi Earthquake”,  supports that this fault is currently growing.

The study adopted a multi-scale approach combining high-resolution bathymetric data to obtain the three-dimensional morphology of the Al-Idrissi Fault System with a high level of detail. The Al-Idrissi fault is a unique model that shows the generation and growth of an active fault. In the last thirty years, three seismic events have been recorded (in 1994, in 2004 and in 2016). The accumulation of earthquakes can lead to the generation of longer faults with the potential to generate earthquakes of greater magnitude over time.

"Now that we know in detail this growing fault structure, we can establish more precisely the potential seismic evolution of this system," says the ICM-CSIC researcher.

This study involved researchers from 10 institutions: Institut de Ciències del Mar - CSIC (Barcelona), GEOMAR Helmholtz Centre for Ocean Research (Kiel, Germany), Scripps Institution of Oceanography - UCSD (La Jolla, San Diego, USA), Irish Centre for Research Center in Applied Geosciences (iCRAG) University College Dublin (Dublin, Ireland), Institute of Earth Sciences “Jaume Almera” - CSIC (Barcelona), Institute de Physique du Globe de Paris (France), National Oceanography Center (Southampton, UK), Unitat de Tecnologia Marina-CSIC (Barcelona), Sorbonne Universités - UPMC (Paris, France) and the Institució Catalana de Recerca i Estudis Avançats (ICREA, Barcelona).


Tectonic setting and seismicity in the Alboran Sea. The white star depicts the 25th January 2016, Mw 6.4 earthquake event.



Source: Eulàlia Gràcia, Ingo Grevemeyer, Rafael Bartolomé, Hector Perea, Sara Martínez-Loriente, Laura Gómez de la Peña, Antonio Villaseñor, Yann Klinger, Claudio Lo Iacono, Susana Diez, Alcinoe Calahorrano, Miquel Camafort, Sergio Costa, Elia d’Acremont, Alain Rabaute & César R. Ranero. Earthquake crisis unveils the growth of an incipientcontinental fault system. Nature Communications. DOI: