The importance of subduction for the modern stress field in the Tyrrhenian area

Abstract

The Tyrrhenian sea was formed by lithospheric extension in a context of continental convergence between Africa and Eurasia. At present, a compilation of strain and stress indicators in this region by Rebai et al. (1992) shows that an extensive regime is still predominant in the Tyrrhenian sea while northern Italy and southern Sicily are undergoing compression. This tectonic configuration is the result of two major contributions which act on a very heterogeneous lithosphere: the Africa‐Eurasia collision, on the one hand, and the subduction along the Calabrian arc, on the other. The latter is expected to create a ‘trench suction force’ on the overriding Tyrrhenian plate. The objective of this paper is to investigate the relative importance of these contributions using a numerical model developed by P. Bird (1989) based on an improved version of the ‘thin plate’ approach which models lithospheric deformation in an horizontal plane. The results of this model demonstrate the necessity of considering the forces related to subduction to understand the modern stress and strain field. An extrusion mechanism alone cannot explain present‐day observations. The salient features of the current tectonic regime are reproduced by the model which, however, predicts more limited extension than expected. Further work will be needed to find a better tuning of the parameters and ascertain the quality of available data.