The 6th February 2023 tsunami in the Eastern Mediterranean: on the origin of the event

On 6 February 2023 the region between southern Turkey and northern Syria was hit by a devastating earthquake sequence, starting with a Mw = 7.8 event at 01:17:34 UTC on the Eastern Anatolian Fault (EAF), followed by a Mw = 7.5 at 10:24:29 UTC along the Sürgü Fault (SF). Due to the comparable size of the two events and the mutual positions (on two separate structures, EAF and SF), they are considered “doublet” earthquakes. Aftershocks occurred for few weeks after the first mainshock (Mw=7.8) and many different coseismic and secondary effects accompanied the seismic sequence. The Mw=7.8 event was followed by a modest tsunami that was observed on few coastal Tide Gauges (TGs) in the eastern Mediterranean. Historical tsunami catalogues contain very few entries of past tsunamis in this area of the Levantine coast. In this work, we aim to constrain the nature and location of the tsunami source through numerical simulations. Two generation mechanisms are considered: the first involves the activation of an offshore tectonic source, while the second considers submarine landslides. The latter are modelled using a combination of two Gaussian functions with opposite polarity as the analytical initial condition. Several scenarios, based on both tectonic and mass movement sources, are tested employing JAGURS, a numerical code that computes tsunami propagation and inundation on the basis of the long wave approximation. The results of the simulations are compared with the observations available, provided by the tide gauge stations of Gazimagusa/Famagosta (Cyprus), Arsuz (Turkey), Erdemli (Turkey) and Tasucu (Turkey), allowing for the identification of a source area capable of reproducing the main characteristics of the observed TG records during the first minutes following the tsunami's arrival. Whatever the type of source considered, none of the tested scenarios is able to reproduce all the main observed characteristics (arrival time, period, polarity and amplitude of the first peak) of the recorded waveforms. At this stage, we favour the hypothesis of a complex generating mechanism, combining a predominant role played by one or more submarine landslides, possibly “tuned” by a contribution from coseismic offshore ruptures.