Upper Mantle beneath Tunisia from Joint Shear-Wave Splitting and Rayleigh Wave Dispersion Analysis

Abstract

The current study aims to continue the analysis of the seismic anisotropy of Tunisia region and complete the previous studies of northwestern Africa, which helped to identify the deformations of the crust and the upper mantel, allowing us to obtain a geodynamic scenario for the southwestern Mediterranean. Tunisia is located on the boundary between the African and Eurasian plates. We used the method of splitting the shear wave SKS analysis of data from nine broadband seismic stations installed in Algeria, Tunisia, and the surrounding islands, Sardinia and Sicily, to explore the seismic anisotropy of this study area. We obtained 2D tomography of the shear wave velocity, Vs, structure of lithosphere and upper mantle depths ranging from 50 to 300 km using the Raleigh wave dispersion curve with the twostation technique in the 10-200 sec period domain. After analyzing hundreds of seismic data, we obtained the following results: multi-layer seismic anisotropy beneath TAMR and THTN seismic stations installed in northern Tunisia, while the southern station TATN has a single layer. The results of Vs-structure imaging of the second method also confirmed these results of the direction and depth of the deformed layers. Four distinct velocity bodies were found: two with low values (Vs is ~ 4 km/s) in the west and the east, and two with high values (Vs is ~ 5.5 km/s) in the north and the south of the study area.