Deciphering the dynamics of the North-South Faults in the Alboran Sea (Western Mediterranean) based on a high-resolution morphometric analysis

Geomorphological approaches are essential for advancing our understanding of fault dynamics and assessing better their seismic hazard, especially offshore where direct geological observations are inherently challenging. This study employs high-resolution bathymetric data (1 m) to conduct a detailed quantitative morphometric analysis of individual fault scarps along the North-South Faults (NSF). Our analysis provides a comprehensive characterization of this fault system, including key morphotectonic features such as tectonic depressions, horst and graben structures, half grabens, and pockmarks. Specifically, the fault scarps morphometric analysis derived from evaluating diverse bathymetric profiles across each fault scarp, reveals distinct patterns of vertical displacement, fault growth, and connectivity along the NSF. Vertical displacement ranges from centimetres to decametres, with the largest scarp and fault displacements consistently located in the southern area. This spatial distribution highlights a progressive northward propagation of the fault system, reflecting its evolving dynamics. The presence of relay ramps, stepovers, and interconnected segments indicates that the NSF is an incipient fault system developing within a left-lateral transtensional regime. Our findings support the interpretation of the NSF as the northern extension of the Al-Idrissi Fault, emphasizing its role within the broader tectonic framework of the Alboran Sea. Furthermore, the potential connection between the faults within the NSF suggests that this system could generate earthquakes up to magnitude Mw 6.1. Considering this, and based on the proposed location and the calculated focal mechanism of the 1910 Adra earthquake, we also hypothesize that the NSF may represent an alternative source for this event. This research highlights the importance of surface process analysis in unravelling fault evolution and its broader implications for regional geodynamics.