Seismology. Main earthquakes recorded

Magnitude of an earthquake

Instrumental measure of its force. It is related with the energy transported by seismic waves. It is expressed in decimal figures in accordance with the Richter scale, whose highest value is 9.

Profundity of the focus of the earthquake

Distance from the point where the earthquake originated and the epicentre or point of vertical projection over the surface of the Earth. It is expressed in kilometres.

Earthquake

Set of shockwaves generated from a point within the Earth, called its focus or hypocentre, as result of which there is a sudden release of energy produced by a brusque movement between blocks of the crust and the mantle of the Earth. They are defined by the following: magnitude and depth of the focus.

The Western Mediterranean is located in a collusion zone between the European and African tectonic plates.

The Seismology Service was created in 1981 to study in detail the seismic activity in the territory, to monitor it closely, and to determine and characterise the seismic zones.

Since 1984, hypocentral determinations have been conducted in consideration of the Service's own data and that of other bodies: the Midi-Pyrénées Observatory, the Institute of Catalan Studies, the National Geographic Institute, the Ebro Observatory, the Fabra Observatory and the Detection and Geophysical Laboratory. Information on seismic activity in Catalonia and its neighbouring regions is released annually in the Seismic Bulletin published by the Geological Institute of Catalonia.

The criterion was to select all the seismic movements those that had an epicentre within the Catalan territory and were of a magnitude equal to or higher than 1.7 on the Richter scale.

Provisional data.