The Gulf of Corinth is a young continental rift that splits mainland Greece, separating the Peloponnese from central Greece along a corridor of active normal faults. It is one of the fastest-extending regions on Earth, widening by up to 15 millimetres per year as the crust stretches and thins.
The rift is bounded by steep normal faults, mostly dipping northward, that drop the gulf floor down relative to the mountains on either side. This rapid extension produces frequent, shallow earthquakes and has carved a deep marine basin flanked by uplifted, faulted terraces along the southern shore.
The faults generated the 1995 Aigio earthquake (magnitude 6.4), which killed 26 people, and the destructive 1981 Alkyonides sequence east of the gulf. Ancient Corinth and the surrounding region have been repeatedly damaged over millennia, making this one of Greece's most closely monitored seismic laboratories.