Friday 15 July 2011

The Portsmouth Earthquake of 14 July 2011

On the 14th of July 2011, slightly before 7.00 am GMT, or just before 8.00 am British Summertime, an earthquake was felt on the South coast of England from Portsmouth to Eastbourne, lasting 2-3 seconds, though no damage or injuries were recorded. The actual epicenter of the quake was about 85 km to the southeast of Portsmouth. The quake occurred at a depth of about 10 km.

The epicenter of the July 14 Earthquake.

The British Geological Survey record that the quake was followed by two aftershocks at 14.30 and 21.55 local time, both with magnitudes of 1.8, though the Centre Sismologique Euro-Méditerranéen in Strasbourg recorded them both as having magnitudes of 2.4.

Seismograph of the July 14 Earthquake, as recorded by the BGS seismometers on Jersey, and at Herstmonceux in Sussex.

The English Channel is not normally though of as being a tectonically active area, but it is affected by movements elsewhere. The expansion of the Atlantic is pushing Europe to the east, and the northward drift of Africa pushes Europe northward as well. The North Sea and the Bay of Biscay are both extensional basins; the North Sea is pushing Britain westward, relative to Europe and the Bay of Biscay is opening and causing Iberia to rotate anti-clockwise.

The British Geological Survey is interested in hearing from anyone in the area who felt (or didn't feel) the Earthquake, information which helps them build up a picture of the event. You can fill in an online questionnaire here.

See also The Newton Abbot Earthquake, The Cornish Tsunami and Earthquakes on Sciency Thoughts Youtube.