Tsunamigenic potential of flank instabilities of Kameni Volcano inside Santorini Caldera, southern Aegean

Located in the southern Aegean Sea, the Santorini volcanic complex represents one of the most geodynamically active and hazardous volcano–tectonic systems in the Mediterranean. Following the Late Bronze Age caldera-forming eruption (~ 1600 BCE), the Kameni volcanic edifice emerged within the central caldera. On the northwestern flank of Nea Kameni, lava flows are superposed on unconsolidated pyroclastic deposits, primarily pumice and ash attributed to the 726 CE submarine explosive eruption. These units reside on a topographic step coincident with a major volcano–tectonic lineament, a geomorphological configuration that exhibits structural parallels to the pre−2018 sector collapse state of Anak Krakatau. Here, we employ the Landslide-HySEA numerical code to simulate tsunami generation and propagation resulting from various potential flank instability scenarios of Nea Kameni. Three distinct collapse volumes were modeled: 0.057 km3, 0.077 km3, and 0.13 km3. The simulations demonstrate substantial hazardous potential; a flank failure of 0.13 km3 has the potential to generate maximum coastal wave amplitudes of up to 39 m. Furthermore, all modeled scenarios result in tsunami heights exceeding 2 m at multiple critical coastal locations. These results indicate that such events would inflict severe damage on critical infrastructure and high-density maritime hubs situated along the inner caldera cliffs. Seafloor microbathymetry acquired through a photogrammetric tow-sled system suggests little remobilization despite ongoing volcano–seismic activity. Yet, our findings underscore the necessity for continuous monitoring of the structural stability of the Kameni volcanic edifice and emphasize the requirement to integrate flank-collapse mechanisms into the tsunami hazard assessment frameworks for Santorini.