Sismotectónica en relación con la Zona de Fractura Azores –Gibraltar: Análisis del terremoto de 12 de febrero de 2007, SO del Banco de Gorringe

Abstract

This work deals with the analysis of the seismicity and tectonic evolution of the eastern end of the Azores – Gibraltar Fracture Zone. The location of the main seismogenetic areas in this region is related to the complex geometry of the boundary between the Iberian and African lithospheric plates. To the west of the San Vicente Cape the seismicity can be related to a local compression at the Gorringe Bank. A detailed seismotectonic analysis allows the geological interpretation of the position of the hypocenter for the 12th February 2007 earthquake. It had Mw 6.0 and was placed on a fault having a NNE-SSW strike and a high dip to NW. The fault shows an oblique displacement (sinistral) and locates in the margin of the Horseshoe abyssal basin. Displacement along this fault is here tentatively related to complex deformation in the outer swell of an incipient downgoing plate. This can be the first indication of the beginning of subduction of the northern part of the African plate under the continental margin of Iberia. On the other hand, an analysis of the location of earthquakes having Mw >6.0 generated to the SW of the San Vicente Cape and the estimated isoseismal map has been made. It can be noted the importance of the uppermost crustal materials on the seismic intensity measurement. Sea waves resulting from these earthquakes and measured in the littoral of the Huelva province have an average velocity of propagation of approximately 600 km/h