# New Insights on the Seismic Activity of Ostuni (Apulia Region, Southern Italy) Offshore
Seismic monitoring in Italy is managed by the National Institute of Geophysics and Volcanology (Istituto Nazionale di Geofisica e Vulcanologia--INGV) through the National Seismic Network (\"Rete Simica Nazionale\"--RSN), whose code, within the International Federation of Digital Seismograph Networks--FDSN--is IV. At present, this network has only three seismic stations (NOCI, MESG and SCTE) operational in Southern Apulia, after the closure of two other stations (LCI and BRT) in 2006. In recent years, the seismic  
Figure 1: Structural sketch of Italy and surrounding areas (modified from [PERSON] et al. [5]). The black arrow indicates the slip vectors of Africa vs. Europe and of Adria vs. Europe obtained from geodetic data. Adria RP is the Adria rotation pole. The red square delimits the area analyzed in this paper. monitoring of this region has been supported by five seismic stations (TAR1, MASS, FASA, CGL1 and PE1) managed by the Seismologic Observatory of the University of Bari (OSUB). The recordings of this network, in conjunction with those of the RSN, allowed for the detection of several low energy earthquakes, such as the M\({}_{\rm L}\) 2.8 event of 5 May 2012, which occurred near Ostuni and was felt by many inhabitants. To improve the seismic monitoring of the Apulian territory, in 2013, thanks to the European project INTERREG, and in collaboration with INGV, the University of Bari (UniBa) installed a local seismic network covering the entire territory of Apulia, the OTRI-ONS network (FDSN code OT). The OT network also incorporated some stations already operating in Southern Apulia, previously managed by OSUB (Figure 2). The details on the operation of the OT network from 2013 to 2019 are described in [PERSON] et al. [10]. Since 2021, other stations have been added, and in 2024, some sensors have been replaced (for further details, see the page \"[[https://www.fdsn.org/networks/detail/OT/](https://www.fdsn.org/networks/detail/OT/)]([https://www.fdsn.org/networks/detail/OT/](https://www.fdsn.org/networks/detail/OT/)) (accessed on 30 October 2024)\"). From May 2019, the OT registrations are available also on EIDA (European Integrated Data Archive) INGV node and can be used to detect earthquakes on Italian territory. As a result, the OT network has improved the detection of earthquakes throughout the territory of Apulia and Southern Italy, as demonstrated by the earthquakes listed in the ONT (National Earthquake Observatory) section of the INGV website. The most energetic event ever recorded by seismic networks in Central-Southern Puglia occurred on 23 March 2018, with Mw = 3.7 and M\({}_{\rm L}\) = 3.9; this earthquake occurred  
Figure 2: Seismic stations used in this study: in red, those belonging to seismic network managed by UniBa (OSUB/OTRIONS); in blue, those belonging to other seismic networks (IV, IX, GE, MN, CR, AC and TV). in the Southeast Murge Adriatic offshore, at the transition between the Apulian Foreland and the Dinarides-Albanides foredeep domains, about 10 km from the town of Ostuni, one of the most touristy and populated municipalities in the province of Brindisi. This event was analyzed in a previous work by [PERSON] et al. [11] to retrieve the geometry of the seismogenic structure responsible for this earthquake, but the authors used the information as downloaded from ONT, before the OT network was integrated into the RSN. Due to the lack of seismicity and of seismic monitoring, no information is available on the tectonic stress regime for the Apulia foreland area in the Italian Present-Day Stress Indicators database [12] (IPSI, [[https://ipsi.rm.ingv.it/](https://ipsi.rm.ingv.it/)]([https://ipsi.rm.ingv.it/](https://ipsi.rm.ingv.it/)) (accessed on 30 October 2024)). Furthermore, no potential seismogenic faults capable of producing significant permanent tectonic deformation at the surface (capable faults) are reported for this area in the Database of Individual Seismogenic Sources [13] and in the database of active capable faults of the Italian territory [14].