Early in the morning on the 22 June 2012 the good folks in the Fuenlabrada district in the South West of Madrid probably slept soundly as an earth tremor of 1.6 on the Richter scale gently burred their beds. This was the start of a cycle of small quakes (around magnitude two on the scale) throughout the South of Madrid and since then 29 tremors have been recorded.
According to Emilio Carreño, head of Red Sísmica Nacional, this isn't the norm in what is actually the most seismically-calm part of the whole Spanish peninsula.
On the 4 October there was another (this time clearly perceivable) tremor registering magnitude 3 in Alcorcón — the actual epicentre of all these seismic events.
No need to pack your bags yet
Carreño postulates that the gradual collision of African and European continental plates may be causing fractures in the granite masses below central Spain. It was this same process that was responsible for creating the Sierra Norte (the mountains you can see to the north of Madrid). There's no real cause for alarm, he adds, as these processes are very slow and the possibility of a violent rupture is remote.
Madrid quake history
The biggest quake registered with its epicentre in Madrid (magnitude 4) was on 27 June 1954 in San Martín de la Vega and caused a few cracks in buildings and some books to fall off shelves.
(Source: 20 Minutos)