The United States Geological Survey recorded a Magnitude 4.0 Earthquake at a depth of 12 km, about 25 km to the southeast of the town of Tomelloso in the Castilla-La Mancha region of Spain slightly after 5.15 pm local time (slightly after 4.15 pm GMT) on Monday 23 February 2015. There are no reports of any injuries associated with this event, but it was felt over much of southern and central Spain, and there are a number of reports of minor damage to buildings.
The approximate location of the 23 February 2015 Castilla-La Mancha Earthquake.Google Maps.
Earthquakes are unusual in central Spain, and the event has been linked locally to the practice of oil extraction by hydraulic fracturing ('fracking'), which has been allowed in the area and which is known to have caused minor Earthquakes in other regions. Hydraulic fracturing, and other forms of injection well drilling, involve pumping high pressure water or other fluids into strata, which can lead to increased stress and lubrication upon faults in the area. However both the depth and the magnitude of this event suggest that fracking is unlikely to have been the cause on this occasion; a depth of 12 km is much deeper than that at which oil extraction occurs in the area, and while fracking has been attributed as a cause for quakes slightly over Magnitude 4.0 in the past (which can cause damage and occasionally injuries), the scale upon which Earthquakes is measured is logarithmic, so that a Magnitude 5.0 quake involves the release of ten times as much energy as a Magnitude 4.0 quake, which does not completely rule out fracking as a cause but suggests that if it is then this is a novel event not encountered before.
The quake is more likely to be related to Spain's location on the Iberian Peninsula and the natural tectonic stresses encountered there. 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.
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