Update on the Compressional Tectonic Evolution of the Tizi n’Test Fault Zone (Western High Atlas) and Its Relation to the Al-Haouz Earthquake of 8 September 2023

ABSTRACT Recently, the High Atlas, a typical intracontinental belt in Morocco, has been the site of intense seismic activity—the “Al-Haouz earthquake”—reflecting the continuation of seismotectonic activity to the present day in this belt. Based on the analysis of the published focal mechanism solutions and referring to previous work on the geodynamic and seismotectonic evolution of the Western High Atlas (WHA), a geodynamic model is proposed linking the source of the earthquake to major reverse faults of the Tizi n’Test fault zone (TTFZ) in response to a submeridian Atlasic shortening. At depth, we propose that this fault zone is probably linked to the lithosphere–asthenosphere boundary plane north of the mantle dome, well known for its seismotectonic activity and thermal anomaly. The seismotectonic activity of the TTFZ makes it one of the major faults in Morocco, accommodating the convergence of the Nubian and Eurasian lithospheric plates. Currently, this movement follows the north-northwest trend in a transpressive system at the contact zone between the two plates. In the WHA, Atlasic compression can be separated into (1) an early phase of north-northeast–south-southwest compression that started at the end of the Cretaceous, (2) a phase of northwest–southeast compression of Mio–Pliocene age, and (3) a phase of north-northwest–south-southeast compression since the Quaternary.