Abstract

This study delves into the present-day seismotectonic conditions beneath the intracontinental High Atlas Mountains, Morocco, with a focus on the region of the significant Al Haouz earthquake on September 8, 2023. the analysis encompasses over twenty moderate seismic events recorded since 2009, utilizing a database of high-resolution seismic recordings (magnitudes ranging from 3.5 to 7) collected by networks established between 2008 and 2024. The primary objective is to refine preliminary earthquake relocation, initially based on P-wave arrival times, by incorporating residual travel-time data from each hypocenter pair to seismic stations. Results from these methods are nearly identical, with the double-difference method yielding the most accurate outcomes. Seismic activity in the region, with depths not exceeding 30 km, appears Skin-Deep, consistent with observations from the latesst Al Haouz earthquake, occurring at a depth of 31 km. The present-day tectonic regimes along the High Atlas system (western and central parts) are determined through inversion of regional seismic moment and tectonic stress tensors. Focal mechanism solutions for well-located earthquakes are calculated using P-wave first motion polarities and regional moment tensor inversion. Subsequently, tectonic stress tensor properties are derived through inversion of focal mechanism parameters. Most seismic events analyzed exhibit focal mechanisms characterized by pure reverse faulting or reverse faulting with a strike-slip faulting component. The orientation of P, B & T axes is 16/189, 39/036, and 08/104 respectively. Estimated stress tensor parameters suggest σ1 axes trend N-S in the Western High Atlas and NW-SE to NNW-NNE in the Central High Atlas. These tectonic regimes align well with GPS velocities and neotectonic data, elucidating the tectonic deformation process observed in the High Atlas, particularly in concordance with characteristics of the Al Haouz earthquake beneath the Western High Atlas area.