Seismic And Asismic Deformation In The Beticas-Rif-Alboran Area

We analyze the repartition between seismic and aseismic deformation in the Betic and Rif cordilleras and the Alboran Sea from a comparison between GPS measurements of geodetic deformation and seismic moment release. The seismic deformation tensor, obtained from summing solutions of the Instituto Andaluz de Geofisica (IAG) moment tensor catalogue, indicates a deformation regime with principal compressive axis at N149 degrees E and principal tensional axis at N59 degrees E. Average deformation rates over the last 21 years are about 4,4.10(-17) s(-1), including the sum moment tensor and the estimated contribution of other earthquakes with M-W >= 0, inferred from magnitude regressions, the estimate of seismic consistency and the b value from the Gutenberg-Richter relation. The comparison with geodetic deformation rates of 1,7.10(-16) s(-1) in similar to N150 degrees E direction and 1,9.10(-16) s(-1) in direction similar to N60 degrees E, indicates a seismic coupling of similar to 24%, while the 76% remainder might be generated in aseismic processes or be accumulating as elastic deformation. The b-value of the Gutenberg Richter relationship is 1.25 in the study area, which suggests that the microseismicity contributes significantly to seismic moment release. This observation limits the dependency of the results on the largest regional earthquakes, which are distributed irregularly in time, and are probably not represented adequately in available seismic catalogues.