Insights into the September 8, 2023, MW 6.8 earthquake in Morocco: a deep transpressive fault along the High Atlas Mountain belt

Abstract

On September 8, 2023, a magnitude 6.8 earthquake impacted the High Atlas Mountains in western Morocco, approximately 70 km southwest of Marrakesh, resulting in significant devastation and casualties. This study delves into a comprehensive geodetic dataset, utilizing interferometric synthetic aperture radar (InSAR) measurements to analyze the fault segment accountable for the seismic occurrence. Our findings propose two potential fault scenarios: a transpressive NNW-dipping high-angle fault (70°), associated with the Tizi n’Test alignment, or a transpressive SSW-dipping low-angle fault (22°) linked to the North Atlas Fault, where slip (up to 2.2 m) is observed predominantly in deeper sections of the fault. Although seismic catalogs were inconclusive regarding the dip direction of the fault, evidence from mainshock locations, gravity and heat-flow data, along with modeling, and the active shortening direction, collectively indicate the activation of a low-angle, southwesterly dipping oblique thrust of the North Atlas fault during the 2023 Moroccan earthquake. Integrating interferometric analyses with geological, tectonic, and seismological data could be crucial for resolving ambiguities in satellite-based models. This study therefore underscores the complexity of fault identification and the need for a multidisciplinary approach in understanding seismic events.