Unlocking the hidden secrets of the 2023 Al Haouz earthquake: Coseismic model reveals intraplate reverse faulting in Morocco derived from SAR and seismic data

Abstract

The 2023 Mw 6.8 Al Haouz earthquake struck Morocco’s Atlas Mountains on September 8, causing over 3000 fatalities and extensive damage, revealing hidden seismic hazards in this slowly deforming region. Despite its impact, Al Haouz earthquake has received limited scientific investigation. The absence of surface rupture, its occurrence in an intraplate seismic silence zone, and ambiguous focal mechanisms have hindered understanding of the fault’s kinematics. To address these gaps, our study employs the Interferometric Synthetic Aperture Radar (InSAR) technique to refine the coseismic deformation. We further propose two fault-dipping scenarios, northward and southward, reinforced by a unique local seismic dataset to evaluate the fault rupture characterization. Additionally, stress change analysis assessed the stress transfer effects between the mainshock and aftershocks, culminating in a comprehensive geodynamic model. Our findings reveal a northward-dipping reverse fault with a strike of $249.8^{\circ }$, a dip of 66°, and a rake of 55°, exhibiting a maximum slip of 1.75 m. Stress change analysis demonstrates that stress transfer from the mainshock reactivated pre-existing faults, particularly the Tizi n’Test fault system, triggering shallow aftershocks in high-stress zones. We suggest that mantle upwelling, coupled with fluid injection along pre-existing faults, drives seismic dynamics in the region. The Tizi n’Test fault likely extends to the lithosphere–asthenosphere boundary, where active upwelling facilitates magma fluid intrusion, stimulating seismic activity. These findings are consistent with recent research, providing deeper insights into fault mechanics in the Atlas Mountains. They also highlight the significant contribution of satellite-based SAR techniques in uncovering hidden seismic hazards.