The United States Geological Survey recorded a Magnitude 4.2 Earthquake at no significant depth roughly 30 km of the coast of the Province of Castellón on Spain's Mediterranean coast, slightly after 3.30 am local time (which is GMT) on Tuesday 1 October 2013. This was followed by a Magnitude 3.9 aftershock at more-or-less the same spot slightly after 11.05 pm on Tuesday 5 October. The original Earthquake was the largest ever recorded in the Gulf of Valencia, and while it did not cause any damage or injuries, it caused some alarm in the town of Alcanar (35 km northwest of the epicenter), which is not used to Earthquakes.
The approximate location of the 1-2 October 2013 Gulf of Valencia Earthquakes. Google Maps.
Iberia is located on the extreme southwest of the Eurasian Plate, close to the margin with Africa, which is pushing into Europe from the south. At the same time there is a lesser area of geological expansion beneath the Bay of Biscay, pushing Iberia southwards. This leads to considerable tectonic stress in southern Spain, leading in turn to the occasional Earthquake.
However the Gulf of Valencia region has not historically been prone to seismic activity, and many people have linked these events to a European Investment Bank-backed project which aims to store natural gas in a depleted oil reservoir in the area. The Escal UGS Castor Storage Plant Project is intended to store up to 1.3 billion cubic meters of gas, and use it to supply Spain's national grid on demand. The first phase of the project, in which seawater was pumped from the reservoir, was completed on 16 September 2013, and initial pumping if gas into the reservoir was due to begin early in October. This has now been halted following a string of small Earthquakes, and complaints from residents' and environmental groups that a promised seismological study on the project was never carried out, despite the project being near a known fault zone. Spain is reliant on imports for almost all of its oil and gas needs, and is extremely vulnerable to fluctuations in prices on international markets.
See also Earthquake of the north coast of Morocco, Magnitude 5.9 Earthquake in the Azores, Earthquake off the coast of Tunisia, Earthquake in southern Spain and Earthquake in northern Algeria.
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