The 8 September 2023, MW 6.8, Morocco Earthquake: A Deep Transpressive Faulting Along the Active High Atlas Mountain Belt

Abstract

On 8 September 2023 an MW 6.8 earthquake struck the High Atlas Mountains of western Morocco, about 70 km southwest from Marrakesh, causing significant devastation and casualties. In this study, we investigate a comprehensive geodetic data set, employing interferometric synthetic aperture radar measurements to assess the fault segment responsible for the seismic event. Our findings suggest two potential fault scenarios: either a transpressive NNW-dipping high-angle (70°) fault related to the Tizi n'Test alignment or a transpressive SSW-dipping low-angle (22°) fault associated with the North Atlas Fault, with slip (up to 2.2 m) only occurring on deeper parts of the fault. While seismic catalogs couldn't definitively determine the dip direction of the fault, evidence from mainshock locations, gravity and heat flow data and modeling, and active shortening direction suggest the activation of a low-angle south-westerly dipping oblique thrust of the North Atlas fault during the 2023 Moroccan earthquake.