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On 23 March 2018, an event of magnitude ML 3.9 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 13 February 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 was identified in the rupture of a small portion of a 40 km length structure with strike NW-SE, dipping at a high angle toward the 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 is quite close to the event's epicenter (about 20 km), together with data coming from the RSN (Rete Sismica Nazionale). Furthermore, we have determined the focal mechanism of some events, with implications on stress field of the area. Our results show right-lateral transtensional kinematics of the seismogenic faults along approximately E-W striking planes, with a tension, T, with a trend of about 60° (NE-SW direction) and a plunge of 20°. Finally, we have tried to correlate the location of the four best constrained earthquakes with their seismogenic structures. [ABSTRACT FROM AUTHOR]

The M w 6.0 earthquake that hit central Italy on 2016 August 24 caused an abnormally high level of destruction in the town of Amatrice. In order to clarify the role of site response in causing such a disaster, a series of ambient noise recordings acquired in the aftermath of the event are analysed here to identify site resonance properties from the ratios H/V between horizontal and vertical amplitudes of ground motion. Although the noise data acquisition was limited by the emergency management activities, the use of a new analysis technique, which isolates the contribution of Rayleigh waves to the noise wavefield and averages instantaneous estimates of H/V ratios, provided more stable results compared to the standard Nakamura's technique based on mean spectral ratios. The results demonstrated the occurrence of significant resonance phenomena, but without an obvious correlation with the spatial distribution of damage severity. It is apparent that the damage severity was also influenced by some additional local factors related to building vulnerability. Moreover, the time-series analysis revealed seasonal variations in the Rayleigh wave ellipticity curves likely related to the water content changes in the surface deposits and their influence on the Poisson coefficient. Finally, the new method proved capable of recognizing time-varying directions of Rayleigh wave propagation. This capability could be exploited to support other passive seismic methods (e.g. ReMi), whose results' reliability is limited by the lack of control on wave direction origin. [ABSTRACT FROM AUTHOR]

The portion of the southern Adriatic Sea, adjacent to the Murge area (Apulian Foreland, Southern Italy), is considered mainly aseismic. The recent March 23rd 2018 earthquake (Mw 3.7), occurred near Brindisi (Puglia Region), giving us occasion to reconsider data coming from different sources (instrumentally-recorded, historically-documented and palaeoseismologically-interpreted earthquakes), that suggest some moderate seismic shocks in this portion of the Adriatic Sea. The present study, based on the re-interpretation of public domain seismic profiles and exploration well logs available in the ViDEPI Project, has been focused on the recognition of faults with Quaternary activity in the epicentral area. A S-dipping fault, with a main dip-slip component of movement, is suggested to be the seismogenic source. Its geometry is consistent with the fault plane solution and the depth of the hypocenter calculated by the INGV (Istituto Nazionale di Geofisica e Vulcanologia). [ABSTRACT FROM AUTHOR]