Microearthquake swarms: scaling and lacunarity

The continental collision between the African and Eurasian plates in the Iberian peninsula is solved with a NW-SE compression with an extensional basin, the Alboran Sea. To explain this paradox, several models have been proposed, including the subduction process of a lithospheric plate. In this study a relocation of the seismicity of the area using a JHD algorithm for the period 1950–1995 has been performed, which shows a specific hypocentre pattern that is not compatible with plate subduction. In addition, the direction of the stresses acting in the area has been determined through a comprehensive study of all existing focal mechanisms, together with calculations for 19 new earthquakes with sufficient data to determine the focal solution. After considering all these data, the absence of intermediate shocks in the central part of the Alboran basin and the predominantly thrusting mechanisms at the borders of the basin, with pressure axes perpendicular to the front, we consider a delamination process as a possible mechanism acting in the area