The Italian present-day stress map

Montone P., Mariucci M.T. and Pierdominici S. Istituto Nazionale di Geofisica e Vulcanologia, Roma – Italy The Italian present-day stress map We present an updated stress map of Italy in terms of horizontal stress orientations considering breakouts, focal mechanisms of earthquakes and fault data in order to better define the tectonic structure orientations in the crust. New data focusing in particular on three areas (Abruzzi, central-southern Apennines and Sicily) will be presented. The new data have increased the previous present-day stress compilation of about 20%. We have performed borehole breakout analysis in 57 deep wells and inferred 41 new reliable horizontal stress orientations. In order to resolve also the stress regime we have considered the focal mechanisms of earthquakes computed for these zones. In the Abruzzi region (central Italy) we have analyzed in detail two deep boreholes close to the Mw=6.3 earthquake (April 6, 2009) which destroyed the old town of L’Aquila and caused the death of more than 300 people. In the wide area belonging to the central-southern Apennines, new horizontal stress orientations confirm the NE-extension along the belt and the foredeep, although evidence some local variations. Stress data along the Tyrrhenian coast are relevant, as very few data existed before. Shmin orientations in this area are quite variable and interpreted as due to an extensional tectonic regime with a sub-vertical σ1 and without a prevailing horizontal stress component. Breakouts from southeastern Sicily and offshore are in agreement with the Africa-Europe convergence ~NNW-SSE oriented. Whereas, in central Sicily the presence of a foredeep running with different orientations, from ~EW to ~NS, produced a complex tectonic setting originating local stress sources.PublishedMelbourne, Australia3.2. Tettonica attivaope