General Area    Detail areas West Center East Balearic

The Betics is the most seismically active region of the Iberian Peninsula. Crustal earthquakes of shallow depth (<40 km) and low to moderate magnitude predominate, with the occurrence of some large destructive historical earthquakes. Intermediate-depth seismicity (40-120 km) also occur in the western part of the Cordillera, extending in an NNE-SSW vertical trend from Málaga to the Moroccan coast. The existence of this seismicity has given rise to different theories about its origin, on which there is still no unanimous agreement. Some of the most accepted theories are the existence of a subduction of the Atlantic oceanic lithosphere under the Gibraltar Arc with an eastward dip that becomes practically vertical at depth or the occurrence of different delamination processes under the Alboran Sea.

Occasionally, there are also some very deep earthquakes located at more than 600 km depth with epicenter in the province of Granada. Their origin is also an open question, but some studies relate them to the presence of an anomalous velocity body observed in this area by seismic tomography, which could be connected or not to the body responsible for the intermediate seismicity, and which would be the product of ancient subduction processes or lithospheric delamination. In addition, it is interesting to note that no earthquakes with depths between 150 and 600 km have been recorded.

The crustal seismicity of the Betic System is largely controlled by the active fault systems that cross the Cordillera, and the predominant focal mechanisms vary according to the type of faults and stress field characteristic of each zone. While in the Eastern zone strike-slip focal mechanisms predominate, in the Central zone normal type mechanisms predominate and in the Western zone, where seismicity is scarcer than in the rest of the Betics, the reverse and strike-slip focal mechanisms predominate.

In the historical catalog, there are several significant destructive earthquakes in this region, mainly in the Eastern and Central Betic Cordillera, with estimated magnitudes between 6 and 6.5 and maximum intensities larger than VIII-IX. Among the largest earthquakes occurred in the Betics northeastern end there are worth mentioning the 1396 Tavernes de Valldigna and the 1748 Estuveny (Valencia) events, and the 1620 and 1644 Alcoy and Muro de Alcoy (Alicante) events. Further south, in the province of Almería, there are noteworthy the 1518 Vera, 1522 Alhama de Almería, and the 1804 Dalías earthquakes. In the Central zone, some of the most important events are the 1170 Andújar (Jaén), the 1431 south of Granada, and the 1531 in the Baza Basin (Granada) earthquakes. In the Western zone, the 1504 Carmona (Sevilla) event, located in the Guadalquivir Basin to the northwest of the Cordillera, and the 1680 Alhaurín el Grande (NW Málaga) event are remarkable. But the largest and most virulent historical earthquakes occurred in this region are the 1829 Torrevieja (Alicante) and the 1884 Arenas del Rey (Granada) earthquakes. Both were felt with a maximum intensity of IX-X and have an estimated magnitude around 6.5.

However, in the instrumental catalog, the largest recorded earthquakes are very deep earthquakes, located south of the city of Granada at depths larger than 600 km, the 1954 Dúrcal (M7.8) and the 2010 Nigüelas (M6.3) earthquakes. At shallow depths, the highest magnitude seismicity occurred in the Betic Cordillera is of magnitude around 5 and maximum intensity of VII. In the Western zone, it is remarkable the 1930 Montilla (Córdoba) event; in the Central zone, two events in 1951 to the southwest of the province of Jaén and the 1956 Purchil (in the Granada basin) earthquake stand out; and in the Eastern zone, are noteworthy the 1948 Cehegín (Murcia), the 1945 Onteniente (Valencia) earthquakes and the most recent one in 2011 in Lorca (Murcia), which caused nine deaths and numerous damages to buildings in Lorca.