# New Insights on the Seismic Activity of Ostuni (Apulia Region, Southern Italy) Offshore
## 4 Data Selection and Hypocenter Re-Location
When possible, the picking procedure of P and S waves was carried out manually, by visual inspection. These data were integrated with the recordings acquired by the OSUB and OT networks and stored in their laboratories. So, the dataset was collected as follows:  
* From January 2000 to December 2007: time picks of P and S waves were downloaded from the INGV web-service \"[[https://terremoti.ingv.it/?timezone](https://terremoti.ingv.it/?timezone)]([https://terremoti.ingv.it/?timezone](https://terremoti.ingv.it/?timezone)) (accessed 15 April 2024)\" and integrated by OSUB recordings;
* From January 2008 to March 2013: recordings were downloaded from the INGV web-service \"[[https://terremoti.ingv.it/?timezone](https://terremoti.ingv.it/?timezone)]([https://terremoti.ingv.it/?timezone](https://terremoti.ingv.it/?timezone)) (accessed 15 April 2024)\" and integrated by OSUB recordings;
* From April 2013 to April 2019: recordings of the IV network were downloaded from the INGV web-service \"[[https://terremoti.ingv.it/?timezone](https://terremoti.ingv.it/?timezone)]([https://terremoti.ingv.it/?timezone](https://terremoti.ingv.it/?timezone)) (accessed 15 April 2024)\" and integrated by OT network recordings;
* From May 2019 to today: recordings of the IV and OT networks were downloaded from the INGV web-service \"[[https://terremoti.ingv.it/?timezone](https://terremoti.ingv.it/?timezone)]([https://terremoti.ingv.it/?timezone](https://terremoti.ingv.it/?timezone)) (accessed 15 April 2024)\". In the Supplementary Materials, we release the txt file containing all the arrival times of the events analyzed in this paper. The 32 events were relocated with the HYPOELLIPSE code [44], using, in addition to the previously available data, the new recordings and the revised phases derived from the re-picking. Seven different velocity models were tested: those commonly adopted by the INGV, CSTI, AK135 and PREM; and the models specifically proposed for this region by [PERSON] and [PERSON] [45], [PERSON] et al. [46] and [PERSON] et al. [47]. In addition, different values of the \(Vp/Vs\) ratio were tested. Figure 6: Circles (with ID number) and squares indicate the epicenters determined by INGV and resulting from the re-locations, respectively, of the 32 events examined in this work. In red, the events occurred offshore in the Adriatic Sea; in light blue, the events occurred on land; and in blue, the events occurred near Taranto, some of which are likely quarry blast (according to [48]). Black squares indicate municipalities. The results of all of these relocations indicate that the best model for this area in terms of travel-time residuals and hypocenter location errors is that of [PERSON] and [PERSON] (2015), with \(Vp/Vs=1.78\). The parameters of relocation of the 32 events are reported in Table 2 and plotted on the map in Figure 6. The velocity model is shown in Table 3.  
Some of the events in Table 2 had already been localized by [PERSON] et al. (2018) (ID: 10, 13, 16, 17 and 19), who analyzed the seismicity in the \"Penisola Salentina\" seismic district, an area much larger than that analyzed in this paper. Regarding the seismicity around the city of Taranto, some earthquakes (for example the one with ID 9) are most likely quarry blast (according to [PERSON] et al. (2018)). We observe a reduction in the hypocentral errors (generally less than 5 km) and in the minimum epicentral distance (Dmin), which is reflected in the lower value of the RMS (on average, from 0.37 s to 0.26 s) with respect to the ONT catalog; instead, we do not observe a significant improvement in the azimuthal gap since the azimuthal coverage of the network has not changed. The variations in the epicentral location are almost always less than 5 km: only for events 2 and 3, the variations are greater than 15 km, but for these events, no repickings were carried out.