No damage has been reported.
The tremor occurred at 9:31 AM today at sea, west of the island and 25 kilometres below the sea surface, some 300 kilometers west of the capital Athens, the Institute of Geodynamics at Athens University reports.
Since January 26, Kephalonia has been struck by 2 quakes over 5.0 in magnitude, and hundreds of aftershocks over 3.5, resulting to damage in some 3,000 houses, according to authorities.
The island, which was flattened in 1953 by 3 successive earthquakes, culminating in a 7.2 tremor, lies in a very active seismic area.