## 4 Summary--Conclusions  
This study examined seismicity in the region of Crete and neighbouring areas recorded by stations of HUSN from June 2018 until the end of May 2023 [66, 67, 68, 69]. This included crustal earthquakes on the island and moderate events that occurred both onshore in local faults and offshore on the HT. These events were used to obtain local 1D velocity models using the mean travel-time residuals and location error minimization technique. Based on these models and the calculated travel times, a new catalogue of seismic events with well-constrained hypocentral parameters was compiled. In the next stage, this catalogue served as input data in order to ameliorate the absolute and relative locations with hypoDD. Both local and regional active faults in the area were highlighted with new results in our effort to obtain a more detailed image of the activated fault structures onshore and offshore of the island of Crete. Figure 11: Depth cross-sections corresponding to the profiles shown in Figure 10. Black dots represent hypocentres of the relocated earthquakes in the broader study area. Projections of the nearest toponyms, fault zones, and moderate ruptures are shown at the top of each section. The newly developed velocity models in this research share several characteristics with those developed by [28; 33; 39; 64]. The primary difference is that the models of [39; 64] produced substantially shallower events than the events that belong in the Arkalochori seismic sequence in Central Crete [63]. In particular, the stronger events of that sequence (Mw = 6.0 and Mw = 5.3) were located at very shallow depths (H < 5 km), which looks improbable in terms of earthquake physics and the area's history [65; 66; 67]. The local 1D models in the first two areas west of the study area (Antikythera-Chania, Rethymno) have a relatively simplified structure since they are composed of four and three layers, respectively. Ref. [53] showed a more detailed image of the upper crust using data from seismic surveys conducted in the area. Their P-wave velocity model is composed of four (4) layers in the uppermost 2 km and reaches 5.2-5.3 km/s below 4 km of depth. The existence of a thick layer of recent deposits (Neogene to Quaternary) above the Alpine basement of different ages and lithology and the top of the low-angle subducting lithosphere (Figure 11) may explain why the velocity structure in Central Crete is divided into numerous layers. Our results show a fair correlation with the ones of [53] for the uppermost (<10 km) part of the crust. Precisely, that study estimated a P-wave velocity between 4.8 and 5.5 km/s. The model developed in the eastern portion of the island suggests a simple layout with four (4) strata (Figure 6a). The V\({}_{\rm P}\)/V\({}_{\rm S}\) ratio of the 1D model developed in Western and Eastern Crete is higher (1.77) than those of Central and SE Crete (1.74 and 1.75), which could be related to the closer location of the intermediate depth events reflecting an upward migration of fluids resulting from the dehydration of subducting sediments within the oceanic origin Tethys plate like in comparable cases [54; 55; 56; 57; 58; 59; 60; 61; 62]. The subduction of the Tethys oceanic lithosphere under the Aegean microplate results in velocities from both plates overlapping, making it difficult to address each plate individually in local 1D velocity models. The relocation procedure managed to improve the relative locations of the 2018-2023 seismic catalogue, which are concentrated in the vicinity of the main local and regional fault zones. The main N-S striking offshore normal faults of the Cretan Sea were highlighted in sub-regions 1 and 2. More specifically, a differentiation in the dip angle of the moderate-size local faults from one corner of the study area to the other becomes evident.