Reicherter, K., Jabaloy, A., Becker-Heidmann, P., Galindo-Zaldívar, J. (2003): The seismotectonic framework of southern Spain – Palaeoseismicity, archaeoseismicity, tsunamis and neotectonics. Geophysical Research Abstracts 5: 5442–5443

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Abstract:

The seismicity of southern Spain, situated at the westernmost edge of the Afro-European Convergence Zone, is characterized by frequent moderate to strong earthquakes which occurred during the Holocene. A large quantity of descriptions of earthquakes and secondary effects, that have been felt in southern Spain during the last 2.000 years, is available in various catalogues. The seismicity is distributed along several active faults in the Betic Cordilleras. We characterize the Holocene faulting history along major fault systems with an integrated palaeoseismic, neotectonic and historical study. One of the most destructive earthquakes in Spain occurred at December, 25, 1884, near Arenas del Rey, along the E-W striking Ventas de Zafarraya Fault (VZF) located in the Granada depression. Palaeoseismic data bracket the timing of pre-1884 ruptures along that fault during the last 10.000 y, indicating earthquake recurrence intervals between 2.000 and 3.000 y for major earthquakes of M > 6.5. The Holocene slip rate was estimated between 0.14 and 0.45 mm/a. The most important deformation and secondary features in this area, like rockfalls, landslides and liquefaction, are related to the activity of the VZF. The Carboneras Fault Zone (CFZ) represents an active set of sinistral strike-slip faults in southeastern Spain, striking NE-SW. The CFZ separates two crustal segments: the Cabo de Gata Block (Neogene volcanics and sediments) and the metamorphic basement of the Alpujarride Complex with Neogene basinal sediments. Shallow-depth high-resolution imaging of Tyrrhenian beach terraces and recent off-shore deposits exhibited both vertical and horizontal offsets and folding in the Gulf of Almería. The last major earthquake along the CFZ occurred on September, 22, 1522, near Almería associated with large damage of several cities and a tsunami. The results suggest a distributed tectonic activity along the CFZ during the Late Quaternary, with an off-shore epicentre for the last event. For other strong earthquakes along the Andalusian Coast, e.g. the October, 9, 1680 Malaga event and the 40-60 AD and 350-395 AD events which destroyed the Roman village Baelo Claudia in the Straits of Gibraltar, also off-shore activity of faults is suggested. Our approximation of the seismic history of a individual fault or fault system in terms of recurrence or maximum expectable earthquake contributes to the seismic hazard assessment of the area, which to present lacks the incorporation of palaeoseimic and archaeoseismic data.