Unravelling the AMORGOS 1956 tsunamigenic earthquake: Advancing Seismic and Tsunami Risks Assessment in the Eastern Mediterranean – AMORGOS

In recent decades, the perilous nature of offshore earthquakes and their ability to trigger devastating tsunamis has become increasingly evident. Historical and contemporary accounts of tsunamis in the Mediterranean region are compiled in European tsunami databases, contributing to our understanding of natural hazards and their geographical occurrence. However, the sources of most of these tsunamis are unknown: the causative faults that slipped and displaced the seafloor are still unidentified. This lack of knowledge extends to key rupture parameters (length, width, slip), and impede our ability to accurately understand the tsunami sources, predict the likelihood of future significant nearby earthquakes, and determine parameters that influence seismic and tsunami hazards.
This is the case for the largest Mediterranean tsunami in the last two centuries, which occurred offshore Amorgos and Santorini islands (09/07/1956). Recently acquired marine geological and geophysical data now allow us to identify the normal fault that ruptured and quantify the surface rupture on the seafloor. Based on these new constraints, our multidisciplinary project aims to establish plausible slip scenarios at depth, validated by tsunami modelling, existing seismological records, and new ground acceleration data, derived from damage studies of buildings. Constrained slip scenarios will inform on how stresses have evolved around the 1956 rupture, and whether they may promote future large earthquakes along neighboring unbroken fault segments. In addition, geological and human archives will be explored in order to reconstruct the unknown rupture and tsunami history in the region. This project will allow important advances in our understanding of telluric hazards in the region, and will take part into vulnerability reduction. It will also provide new insights into the hazards associated with back-arc basins, which are often less considered than those associated with subduction megathrusts.