## 2 Study Area  
### Geological and Seismotectonic Setting  
Lefkada Island is located in the southern Ionian Islands (Western Greece), in the front of the Hellenides orogenic belt, in a region dominated by the presence of the Cephalonia Transform Fault Zone (CTFZ) [54,55]; (Figure 1). The latter is a 140-km long right-lateral fault zone, as evidenced by a large number of focal mechanisms [56, 57, 58, 59]. The study area lies in the transition zone between the subduction of Tethys beneath the Aegean microplate to the south and the continental collision to the north (Figure 1). The CTFZ consists of two major segments, i.e., the Cephalonia Segment (CS) to the south and the Lefkada Segment (LS) to the north. The proximity of Lefkada to the CTFZ is the main reason the island is among the most seismogenic areas in Europe. Regarding the historical era, large and destructive earthquakes have occurred during the last six centuries [60,61] (Figure 2a). Most of these events mainly affected the western coast of the island, such as the 1704 (M = 6.3), 1769 (M = 6.7), 1783 (M = 6.7) and 1869 (M = 6.4) earthquakes [62, 63, 64], (Figure 2a). Thirteen disastrous events that took place at the western onshore area of Lefkada occurred between 1612 and 1869 [64,65]. On the contrary, the 1723 (M = 6.7) earthquake was the sole historical event that occurred at the southwestern part of Lefkada Island [58]. Intense seismic activity has been recorded in the Lefkada region during the 20 th century, characterized by the frequent occurrence of destructive events [66]. More specifically, 87 events with Mw \(\geq\) 4.1 occurred between 1911 and 1998, 36 of which Mw \(\geq\) 5.0 and 5 with Mw \(\geq\) 6.0 (Figure 2a). Both of the largest events of the 20 th century, with Mw = 6.5, occurred in 1948. The first event of 22 April destroyed the southwestern part of the island, whereas the second on 30 June caused damage to the northwestern part [66]. Two large events occurred in the vicinity of Lefkada Island during the 21 st century. The first was the Mw = 6.3 on 14 August 2003, located northwest of the island at a depth of 9 km. Its focal mechanism indicated dextral strike-slip faulting (e.g., [58,67,68]). The most recent destructive event occurred on 17 November 2015 (Mw = 6.4) close to Athani, at the southwestern coast of Lefkada, on an almost vertical dextral strike-slip fault [55,69]. Most aftershocks were aligned parallel to the western coast of Lefkada Island, along an NNE-SSW direction, with another group of epicenters located close to the northern part of Cephalonia Island [63]. The seismogenic layer ranged from 3 to 16 km in depth, whereas more than one fault plane with different strike and dip values were activated [64]. Despite its larger magnitude, this event caused less damage than the 2003 earthquake, proving the structural efficiency of the local buildings [69]. The geological structure of the southern Ionian Islands is characterized by the occurrence of alpine formations of the Ionian and Paxoi geotectonic units and post-alpine deposits lying unconformably on the alpine basement [72; 73; 74; 75; 76; 77]. Similarly, Lefkada is composed of (a) alpine formations that belong to Ionian and Paxoi geotectonic units, (b) molassic formations and (c) recent deposits that lie unconformably on the previous formations [74; 78] (Figure 2a). Ionian formations are observed in the largest part of the island, while Paxoi formations are only observed in the southwestern part of the island and more specifically in the Lefkata peninsula (Figure 2a). As regards the tectonic structure, the faults dissecting the island are mainly normal or strike-slip with a sinistral or dextral sense of shear [77; 79; 80]. The active structures are major faults detected mainly along the margins of fault blocks [77; 77]. In particular, Lefkada is composed of the following 8 fault blocks [78] (Figure 2a):  
1. The fault block of Lefkada town, located in the northeastern part of the island and bound to the south by the Frini-Apolpaena fault zone (FAFZ). 2.