Evidence of active extension in Quaternary volcanoes of central Italy from breakout analysis and seismicity

We present active stress directions obtained from borehole breakout analysis performed on 15 geothermal wells located in the western coastal regions of Central Italy. The study area (a 200 km by 50 km NW‐elongated area bordering the Apennines) includes several Quaternary high‐K alkaline volcanoes active mainly after 0.6 Ma. We analyzed both paper logs and digital data to detect breakout directions, the two techniques yielding similar results. The breakout results show a predominant ENE direction of SHmin, with local deviations in one region (Sabatini volcano) where no seismicity is observed. The comparison of breakout data with stress directions inferred from inversion of microearthquake (M<4) focal mechanisms computed in three of the four volcanoes suggests that the whole area is presently undergoing NE to ENE extension.