Abstract. We present a source solution for the tsunami generated by the Mw 6.6 earthquake that occurred on 2 May 2020, about 80 km offshore south of
Crete, in the Cretan Passage, on the shallow portion of the Hellenic Arc
subduction zone (HASZ). The tide gauges recorded this local tsunami on the
southern coast of Crete and Kasos island. We used Crete tsunami
observations to constrain the geometry and orientation of the causative
fault, the rupture mechanism, and the slip amount. We first modelled an
ensemble of synthetic tsunami waveforms at the tide gauge locations,
produced for a range of earthquake parameter values as constrained by some
of the available moment tensor solutions. We allow for both a splay and a
back-thrust fault, corresponding to the two nodal planes of the moment
tensor solution. We then measured the misfit between the synthetic and the
Ierapetra observed marigram for each source parameter set. Our results
identify the shallow, steeply dipping back-thrust fault as the one producing
the lowest misfit to the tsunami data. However, a rupture on a lower angle
fault, possibly a splay fault, with a sinistral component due to the oblique
convergence on this segment of the HASZ, cannot be completely ruled out.
This earthquake reminds us that the uncertainty regarding potential
earthquake mechanisms at a specific location remains quite significant. In
this case, for example, it is not possible to anticipate if the next event
will be one occurring on the subduction interface, on a splay fault, or on a
back-thrust, which seems the most likely for the event under investigation.
This circumstance bears important consequences because back-thrust and splay
faults might enhance the tsunamigenic potential with respect to the
subduction interface due to their steeper dip. Then, these results are
relevant for tsunami forecasting in the framework of both the long-term
hazard assessment and the early warning systems.