The 2023 Mw 6.8 Morocco Earthquake: A Lower Crust Event Triggered by Mantle Upwelling?

A M6.8 earthquake struck the High Atlas Mountains in Morocco on 8 September 2023, ending a 63‐year seismic silence. We herein attempt to clarify the seismogenic fault and explore the underlying mechanism for this seismic event based on multiple data sets. Utilizing probabilistic Bayesian inversion on interferometric radar data, we determine a seismogenic fault plane centered at a depth of 26 km, striking 251° and dipping 72°, closely aligned with the Tizi n’Test fault system. Given a hypocenter at the Moho depth, the joint inversion of radar and teleseismic data reveals that the rupture concentrates between depths of 12 and 36 km, offsetting the Mohorovičić discontinuity (Moho) at ∼32 km. Considering a strong link between magma activity and failure in lower crust, we propose that the triggering of the earthquake possibly was mantle upwelling that also supports the high topography. Plain Language Summary On 8 September 2023, a devastating earthquake with a magnitude of 6.8, struck the High Atlas Mountains in Morocco, breaking a 63‐year seismic silence. In this work we utilized geodetic, seismic, and seismicity data to investigate the earthquake, pinpointing its origin within the Tizi n’Test fault system at 12–36 km depths and causing displacement of the Mohorovičić discontinuity (Moho), where Earth's crust meets the mantle. Highlighting the impact of the mantle upwelling, this event underscores its significance in shaping regional topography and driving crustal deformation along established faults, leading to unusual, significant seismic activity in areas of minimal plate convergence. This earthquake highlights the importance of incorporating deep crustal dynamics into seismic hazard evaluations, challenging traditional risk models with its implications on earthquake genesis far from tectonic boundaries. Key Points Interferometric radar data, Bayesian inversion techniques and teleseismic data reveal the seismogenic fault and underlying mechanisms The seismogenic fault centered at a depth of 26 km, striking 251° and dipping 72°, closely aligned with the Tizi n’Test fault system We propose that the 2023 M6.8 earthquake in Morocco was possibly triggered by mantle upwelling on a steep fault that offsets the Moho