A 5.1 magnitude earthquake occurred on Monday, at 09:49, at a distance of 231 kilometres southeast of Athens.
According to the Geodynamic Institute of the National Observatory of Athens, the earthquake is located 21 kilometers south southwest of Arkesini, Amorgos.

Two earthquakes were recorded earlier on Monday and late on Sunday in the sea area between Amorgos and Santorini, according to data published by the Geodynamic Institute of the National Observatory of Athens.
At 01:08, an earthquake measuring 4.5 on the Richter scale was recorded 23 kilometers south-southwest of Arkesini, Amorgos, and on Sunday, at 22:55, a 4.2-magnitude earthquake occured 18 kilometers south-southwest of the same area, according to the same source.
Both earthquakes were described as light by the Institute.

See also:

4.5 and 4.2 Richter quakes in the sea area between Amorgos and Santorini

Meeting on earthquake activity near Santorini says current precautions must continue