Recent spatial and temporal changes in the stress regime along the southern Tunisian Atlas front and the Gulf of Gabes: New insights from fault kinematics analysis and seismic profiles

摘要

Tectonic deformations in the southern Atlassic front of Tunisia (SAFT) and the Gulf of Gabes result from the Nubia-Eurasia convergence. This study, based on the inversion of geologically determined fault slip vectors, presents evidences for spatial and temporal changes in the stress state. Fault kinematics analyses reveal a temporal change in states of stress during the Late Cenozoic. A paleostress (Miocene-Pliocene) state is characterized by a regional compressional tectonic regime with a mean N134 ± 09°E trending horizontal maximum stress axis(σ_1). A modern (Quaternary to present-day) state of stress also corresponds to compressional tectonic regime with a regionally mean N05 ± 10°E trending horizontal σ_1. The SAFT corresponds to two distinct domains: a far-foreland Atlassic front related to contractional deformation associated with southward propagate thrusting, and eastward, the Gulf of Gabes characterized by normal component NW to WNWtrending faults at the crustal margin scale probably related with a transtensional tectonic regime. We propose that the spatial and temporal changes in the stress during the Miocene-Pliocene and Quaternary may result from the geodynamic evolution of the Tunisian Atlas in relation to the rotation of Corsica-Sardinia blocks and the separation of the Sicilian continental lithosphere from the Ionian oceanic lithosphere. These temporal and spatial stress changes along the SAFT and the Gulf of Gabes are probably the engine behind the moderate seismicity, leading at the same time to a reactivation of the inherited major structures created during the evolution of the southern Tethyan margin.