Seismicity in southwestern Iberia, although scattered distributed throughout the area, both on land and offshore in the Atlantic coast, seems to be concentrated in clusters of earthquakes mainly in Portugal, in a region around Lisboa in the north central sector (around the Lower Tagus Valley and the Alentejo region), as well as in the southwestern part of the Subportuguese zone and the western part of the Algarve basin. Earthquakes also cluster in the south of the Guadalquivir basin, in the boundary with the western Betics (south of the provinces of Sevilla and Córdoba and north of Cádiz). These are mostly shallow earthquakes (h<30 km) of low to moderate magnitude, although there have been also several large destructive historical earthquakes, reaching maximum intensities (EMS-98) above VII and estimated magnitudes around 6. The available focal mechanisms are scarce, with predominance of strike-slip and inverse fault type, consistent with current tectonics.

In Portugal, the largest earthquakes in the historical catalogue are those occurred in 1531 in Vilafranca de Xira and in 1858 in Setúbal, both with a maximum intensity of IX and estimated magnitudes of 6.5, and the 1909 Benanvente earthquake felt with maximum intensity X and estimated magnitude 6. Around Lisbon, in the Lower Tagus Valley and the Alentejo area, several historical earthquakes with intensity VII and estimated magnitudes between 5.4-5.7 are also worth mentioning. These are the events occurred in 1344 and 1914 in Benavente, in 1903 in Setúbal, in 1906 in Lisboa, in 1909 in Évora and Macas, the latter of estimated magnitude 6 and intensity VIII, and those earthquakes in 1910 in Viana do Alentejo and Estremoz. In the instrumental period, the largest recorded earthquake of this area is the one that occurred in 1926 in Évora of magnitude 5.4 and intensity VII.

In Spain, the largest historical earthquake was recorded to the northwest of Sevilla in 1504, with maximum intensity VIII-IX and estimated magnitude of 6.3. In the historical catalog, it is also noteworthy an earthquake in 1750 in Huelva with maximum intensity VII and estimated magnitude of 5.4. In the instrumental period, the largest earthquakes have been recorded in the Guadalquivir basin, highlighting three M5 earthquakes in the south of the province of Córdoba, in 1930 in Montilla, felt with maximum intensity VII-VIII, and those in 1935 and 1985 in Benamejí and Espejo, respectively, both with intensity V, and an earthquake in 1989 in Ayamonte (Huelva), of magnitude 5.1 and intensity VI. More recently, several notable seismic series felt by the population have occurred in the province of Sevilla, in 2007 in Moron de la Frontera and in 2008 in Coripe, with maximum magnitudes of 4.4 and 4.7, respectively, and maximum intensities of V.