New Insights on the Seismic Activity of Ostuni (Apulia Region, Southern Italy) Offshore

On March 23, 2018, an event of magnitude Mw 3.7 occurred about 10 km from the town of Ostuni, in the Adriatic offshore. It was the most energetic earthquake in south-central Apulia ever recorded instrumentally. On February 13, 2019, in the same area, a second ML 3.3 event was recorded. The analysis of the 2018 event shows that the ambiguity of the solution of the fault plane reported by INGV (Istituto Nazionale di Geofisica e Vulcanologia) on the Italian National Earthquake Centre website can be solved considering existing seismic profiles, exploration well logs and the Quaternary activity of faults in the epicentral area. A seismogenic source is identified in the rupture of a small portion of a 40 km length structure with strike NW-SE, dipping at high angle towards south. In this work, we have relocated the recent earthquakes by using the seismic stations managed by the University of Bari (UniBa), one of which quite close to the event epicenter (about 20 kilometers), together with data coming from the RSN (Rete Sismica Nazionale); furthermore, we have determined the focal mechanism of some events, with implication on stress field of the area.