MODERN TECTONIC STRESS-FIELD IN THE MEDITERRANEAN REGION - EVIDENCE FOR VARIATION IN STRESS DIRECTIONS AT DIFFERENT SCALES

A compilation of more than one thousand stress indicators (which include in situ stress measurements, focal mechanisms, microtectonic and other geological data) allowed us to reconstruct the modern stress field in the Mediterranean region and the surrounding area. Average stress directions at different scales have been reconstructed by means of a linear interpolation method. This method takes into account the distribution, scale and quality of stress data. The results of the interpolation at plate scale, allow us to recognize slightly deformed regions such as the northwestern European platform, where average maximum horizontal stress direction is oriented roughly NNW-SSE, subparallel to absolute and relative plate velocity directions. Other regions such as the Caucasus, Alps and Pyrenees, where recent tectonic deformation and seismicity are present, display important variations of stress directions. The reconstruction of the average stress directions at different scales within the French Alps pointed out that the average stress field pattern may vary from one scale to another. Nevertheless, variations of stress directions at a given scale are consistent with the kinematics of faults of the same scale.