At roughly 5.35 pm local time on Sunday 7 August 2011 an earthquake with a magnitude of 5.0 on the Richter Scale occurred beneath the Gulf of Corinth in Greece. Reports on the depth of this quake vary, with the United States Geological Survey giving a depth of 13.1 km and the Centre Sismologique Euro-Méditerranéen giving a depth of 5 km. Either way this was a shallow quake with the potential to be very dangerous. As it was there are no reports of any casualties or significant damage, but residents on both sides of the Gulf reported severe shaking with things falling from shelves etc.
Intensity map for the Gulf of Corinth quake. The purple star marks the site of the quake, the circles places where people reported feeling the quake. Larger circles indicate more people felt the quake, and the colour represents the intensity felt by the reporter.
Southern Greece and Turkey lie on the boundary between the Eurasian and African Plates on two smaller plates, the Aegean Sea Plate (underlying the Peloponnese, Attica, The Cyclades Islands, Crete, the Dodecanese Islands and Turkey to the southeast of the Taurus Mountains) and the Anatolian Plate (underlying most of the rest of Turkey). Northern Greece and the north coast of Turkey lie on the Eurasian Plate. Both countries are highly prone to earthquakes because of this.
The Aegean Sea and Anatolian Plates.
The Aegean Sea Plate is moving southwest with regard to the Eurasian and Anatolian Plates, and being subducted beneath the African Plate to the south. Its margin with the Eurasian Plate is a divergent and a transform margin at different points. Beneath the Gulf of Corinth it is a transform margin, where the plates are moving apart. In theory such a margin has the potential to become a new ocean, such as the Atlantic, with two continental plates moving apart and a rift zone creating new oceanic crust in between. However this is unlikely to be the fate of the Gulf of Corinth, as the Eurasian Plate is moving south over it (albeit at a slower rate than the Aegean Sea Plate is drawing away), the African Plate is advancing on it from the south, with the Aegean Sea Plate being subducted and destroyed beneath it, and the Anatolian Plate is moving in from the East.
Greece has a long history of Earthquakes. The most recent earthquake related fatality in Greece was in July 2008, when a woman was killed in an earthquake in Rhodes. In June the same year an earthquake on the Gulf of Corinth killed two people and made 2000 more homeless. In the past earthquakes in Greece have tens of thousands of people, caused tsunamis which have devastated the Egyptian and Levantine coasts and destroyed the Colossus of Rhodes. An earthquake which destroyed much of Sparta was one of the events leading up to the Peloponnesian War.
See also Torino (Turin) rocked by mild Earthquake, Recent eruptions on Mount Etna and Earthquakes on Sciency Thoughts YouTube.