Seismotectonic of the Azores-Alboran region

Abstract

New seismicity and focal-mechanism data from the area of the Azores Islands, in the Mid-Atlantic Ridge, to the Alboran Sea and the southern part of Spain are presented. As a consequence of the different characters in the focal-mechanism solutions and b- values associated, the area has been divided in four different parts, namely, Mid-Atlantic and Terceira Ridge, Azores—Gibraltar fault, Gulf of Cadiz, Alboran Sea and Betica. The last two form the interaction between the Eurasian and African continental plates. The fracture zone is the locus of very large earthquakes with mechanisms showing a predominant right-lateral horizontal motion. Seismic foci in the continental interaction zone are spread over the whole region with mechanisms changing in character from west to east. It is suggested that this may be consequence of the behaviour of the Spanish Peninsula as a partly independent subplate. In the eastern part of the studied zone, the so-called Alboran plate may be considered as a buffer plate.