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Since October 2012 till now, more than 2200 low magnitude earthquakes have been located in the vicinity of the towns of Torreperogil and Sabiote (Jaén), in the easternmost part of Guadalquivir Basin, Spain, an area considered of low seismic hazard. Specific tectonic studies in the region are barely available due to the scarce deformation of Mesozoic and Cenozoic cover. However, the reinterpretation of former seismic reflection profiles reveals blind faults in the Variscan basement that could host the swarm. In this work we show the characteristics of the seismic series, including the relocation of earthquakes with magnitude above mbLg 1.5 using the well-known HypoDD code. In addition to a disperse seismicity composed by very low magnitude events that could not be relocated, two clear seismicity clusters with different characteristics were observed. Both clusters showed an approximate N-S striking, probably related to two N-S striking structures. Additionally, we also assessed a statistical analysis of the sequence. The detailed survey carried out in the epicentral area verified the existence of some fault zones. Although it is also possible to observe dip-slip movements, the main zone shows a tectonic fabric with lateral sense of shearing. Their strike and kinematics are in agreement with one of the two nodal planes of the computed focal mechanism.

In this study, a seismogenic source zone model for the Algeria-Morocco region is proposed for seismic forecasting and seismic hazard studies. The delineation includes five zones based on available seismic, geological and geophysical data. Earthquake occurrence process is modeled and analyzed using recent earthquake catalogs compiled for Northern Morocco and Northern Algeria in former studies. In these catalogs, dependent events were identified and removed by adapting Gardner and Knopoff declustering procedure to the study region. Magnitudes of completeness were estimated using different methods, then the Poissonian character of the sub-catalogs obtained for different were analyzed. The procedure developed by Kijko and Sellevoll (1989, 1992) and Kijko and Graham (1998, 1999), including the recent improvement of the maximum possible earthquake magnitude estimator proposed by Kijko and Sing (2011), is used to estimate seismic hazard parameters. The b-value of the Gutenberg-Richter recurrence relationship, taken as an area-specific seismic hazard parameter has been computed using an extension of the Aki-Utsu b-value estimator for incomplete earthquake catalogs (Kijko and Smit, 2012). Then, we derive the activity rate λ(m) for events above the magnitude m, the maximum possible magnitude mmax and its probability distribution function (pdf). These parameters were computed and analyzed for five seismogenic source zones delineated in the Algeria-Morocco region. The second part of this study is related to site-specific seismic hazard, which has been performed in terms of maximum possible acceleration and seismic hazard curves in terms of PGA with a given probability of exceedance in T years, given a hypothetical engineering structure (HES) located at the most populated and industrial cities in the Algeria-Morocco region.