Integrated Geophysical Characterization of the Active Sidi–Thabet Fault (Northeastern Tunisia): Implications for Active Tectonics and Seismotectonics

Abstract

The present-day seismicity reported from permanent networks in northeastern Tunisia is of low to moderate magnitude. However, several damaging earthquakes have been documented in the northeastern region, including the Utica earthquake of 412 and the Tunis earthquakes of 854, 857, and 1957. This seismic activity is a result of the ongoing deformation of tectonic structures in this area. The Sidi Thabet region, dominated by the geological structure of Jebel Ammar, is particularly seismically active, with earthquakes exceeding magnitude 5 and occasionally causing surface ruptures. The Jebel Ammar structure is underlain by a preexisting E-trending fault, referred to as the Sidi-Thabet fault in this study. Geologic, seismic, neotectonic, and geophysical investigations have revealed recent tectonic activity on this fault. Recent surface tectonic markers found along the fault lineament suggest quaternary activity on this fault. Geophysical investigations, including electrical resistivity tomography (ERT) and seismic refraction sections, confirm the fault's recent activity. The results of the focal mechanism analysis agree with the estimates of strike-slip to transpression paleostress from the Neotectonic period. Tectonic activity observed along the fault zone indicates a significant seismic hazard and high seismic risk for the three million residents in the Tunis metropole, located south of the study area.