## 2 Study Area  
The study area is located in southern Greece (Figure 1a) and specifically in the eastern part of the Gulf of Corinth (Figure 1b). The gulf is an active continental rift, with extension rates around 10-15 mm/yr [57; 58] with numerous catastrophic events recognized in the coastal zone [59; 60]. The first results published from the International Ocean Discovery Program (IODP) Expedition 381, which took place from October to December 2017 in the eastern part of the gulf, indicate continuous cycles between marine and isolated conditions of the gulf over the last 700 ka, depending primarily on eustatic high and low stands [61]. Changes in sediment accumulation and bottom water conditions have been assumed so far to be climatically driven [61]. Environmental changes recorded in the coastal areas [62; 63; 64; 65; 66] seem to be linked to the gulf's tectonic activity, from which submarine landslides are triggered [67; 68; 69; 70; 71].  
Vouliagmeni coastal lake, situated in SW Perachora Peninsula (38\({}^{\circ}\)1.714\({}^{\prime}\) N, 22\({}^{\circ}\)52.850\({}^{\prime}\) E), is formed through a tectonic depression and is highly affected by a complex fault system (Figure 1c). The former status of the Vouliagmeni tectonic graben as a bay during the Late Pleistocene was terminated through the tectonic uplift of the area, around the end of the last glacial period [72]. Through a narrow (18 m) canal that was constructed during the 19 th century, the lake has been artificially forced into a more lagoonal state, due to constant interaction with the gulf since then. However, observations of _Lithophaga_ shells in the west coast of Vouliagmeni lake indicate that even in antiquity, the lake water corresponded to that of the sea [73]. The total surface area of the lake is approximately 1.5 km\({}^{2}\) and the maximum depth 49 m. The steep bathymetry, especially at the northern and southern part of the lake, is shaped by normal dipping faults located at the north and south side of the lake (Figure 1c). The drainage system of the Perachora peninsula is attributed to two main networks (Perachora and Pissia) that present different types of evolutionary development [74]. Below 35 m water depth, hypoxic conditions seem to prevail in the lake [75]. The mean water surface temperature is 22 \({}^{\circ}\)C, whereas the bottom temperature ranges from 10 to 14 \({}^{\circ}\)C. The spatial distribution of surficial sediment characteristics and their connection with the hydrodynamic regime have been studied by [76].  
The Perachora peninsula belongs to the Boetian geotectonic zone [77] and is characterized by complex fault systems that strike E-W to ENE-WSW and WNW-ESE (for an extensive geological overview of the area, see [74]). The basement consists of limestones, volcanic and clastic marine deposits (conglomerates/sandstones) (Figure 1c) that are all subjected to massive, tectonically driven movement. Activation of the normal dipping fault systems has been recorded since antiquity [72], causing massive earthquakes and landform dislocation at around 4600-4000 BP, 8 th century BCE, 6 th and 4 th century BCE and 2 nd century CE. Holocene coastal deposits comprise the lake surrounding coastal area and are mostly extended in the eastern part.  
Figure 1: (a) Map of Greece with the study area highlighted. (b) Map of the eastern part of the Gulf of Corinth, presenting the major fault systems (modified from [78]), cities, IODP expedition 381, and the study area. (c) Simplified geological map of the study area based on geological mapping from Hellenic Survey of Geology and Mineral Exploration.