RECENT TECTONIC STRESS FIELD STATE IN ITALY FROM NUMERICAL MODELLING ANALYSIS

San Francisco (California, USA)

We examine the contemporary stress in Italy studying the present-day maximum horizontal stress orientation to characterize the relationship between active stress, past tectonic setting and the seismicity. The
geodynamic setting of Italy is particularly complex. Italy is involved in the N-S convergence of Africa and Eurasian plates and currently undergoing NE-SW extension perpendicular to the Apenninic fold and
thrust belt and with the opening of the Tyrrhenian basin (Late Tortonian).
This process happens in the presence of still active subduction system extending from Sicily to northern Apennines, as confirmed by recently seismicity.
This tectonic setting with highly variable plate boundary events and body forces induced by topography results in an inhomogeneous stress pattern. Here we quantify the spatial changes of the wavelength of the stress pattern by a statistical analysis. As input data we
use 600 data of SH records from the World Stress Map database release 2008 and about 100 new data records. The result of this statistical analysis is a mean orientation of the maximum horizontal compressional
stress SH on a 0.1° grid and the maximum smoothing radius for which the standard deviation of the mean SH orientation is less than 25°. This latter is the wave-length of the stress pattern and reveals for Italy that the entire region has wave-length less than 200 km for Italy.