Stress map of Italy update: new breakout data in southern Apennines

Abstract

Here we present an updated stress map with a focus on southern Apennines. The Apennines are a thrust and fold belt NE-verging characterized by a prevalent extensional tectonic regime. Along the northern front of the belt, from the Po Plain to the Adriatic offshore, compression is on the contrary still active, whereas in its southern part it seems stopped. Indeed, this area is well known as one the most seismic zone in Italy, characterized by strong earthquakes in the past that depict from the analysis of focal mechanisms an ongoing extensional tectonic regime with T-axis about NE-SW. This is also evidenced by the active fault patterns, borehole breakout data and geodetic data. Within this frame, the external area of the Apenninic belt, the foredeep and the Apulian foreland, shows minor seismicity and a prevailing strike-slip tectonics. New borehole breakouts were inferred from wells ranging from 1400 to 5500 depth and are discussed in comparison to earthquake data and a few shallow stress regime indicators. We analysed 45 new deep well data to better constrain the state of stress along the Apenninic belt and foredeep. Some of these are located along the Val d’Agri basin showing a prevalent NE-SW Shmin direction well consistent with the previous results. The most reliable data confirmed the general trend of the southern Apennines but also new insights came out.