The US Geological Survey gave a preliminary magnitude of 5.6, while the European Mediterranean Seismological Center gave it as 5.8. It is common for different seismology centers to give varying magnitudes.
The quake struck at 6:45 a.M. (local time) and had an epicenter beneath the seabed about 140 kilometers (86 miles) south of Athens and near the island of Milos.
Greek radio stations receiving call-ins from listeners said the quake was widely felt across the country, from the southern island of Crete to northern Greece.