The Kefalonia Transform Fault zone is a short but extremely active right-lateral transform in the Ionian Sea off western Greece, linking the Hellenic subduction to the continental collision in Albania. It marks the abrupt boundary where the subducting oceanic crust of the Ionian basin gives way to thicker continental lithosphere.
Slipping at roughly 2 to 3 centimetres per year, it is one of the fastest and most seismically productive structures in Europe, generating frequent strong earthquakes beneath Kefalonia, Lefkada and Ithaca. Its steep, near-vertical geometry produces intense localized shaking on the islands.
The zone has repeatedly devastated the Ionian islands, including the catastrophic 1953 sequence that destroyed much of Kefalonia and Zakynthos, and the paired 2014 Kefalonia earthquakes (magnitudes ~6.1 and ~6.0). Its persistent activity makes western Greece one of the highest-hazard corners of the Mediterranean.