The Campo de Dalias is an area with relevant seismicity associated to the active tectonic deformations of the southern boundary of the Betic Cordillera. A non-permanent GPS network was installed to monitor, for the first time, the fault- and fold-related activity. In addition, two high precision levelling profiles were measured twice over a one-year period across the Balanegra Fault, one of the most active faults recognized in the area. The absence of significant movement of the main fault surface suggests seismogenic behaviour. The possible recurrence interval may be between 100 and 300 y. The repetitive GPS and high precision levelling monitoring of the fault surface during a long time period may help us to determine future fault behaviour with regard to the existence (or not) of a creep component, the accumulation of elastic deformation before faulting, and implications of the fold-fault relationship.
The tectonic structure of the Guadalquivir foreland basin becomes complex eastward evolving from a single depocenter to a compartmented basin. The deformation pattern within the eastern Guadalquivir foreland basin has been characterized by combining seismic reflection profiles, boreholes, and structural field data to output a 3‐D model. High‐dipping NNE‐SSW to NE‐SW trending normal and reverse fault arrays deform the Variscan basement of the basin. These faults generally affect Tortonian sediments, which show syntectonic features sealed by the latest Miocene units. Curved and S‐shaped fault traces are abundant and caused by the linkage of nearby fault segments during lateral fault propagation. Preexisting faults were reactivated either as normal or reverse faults depending on their position within the foreland. At Tortonian time, reverse faults deformed the basin forebulge, while normal faults predominated within the backbulge. Along‐strike variation of the Betic foreland basin geometry is supported by an increasing mechanical coupling of the two plates (Alborán Domain and Variscan basement) toward the eastern part of the cordillera. Thus, subduction would have progressed in the western Betics, while it would have failed in the eastern one. There, the initially subducted Iberian paleomargin (Nevado‐Filábride Complex) was incorporated into the upper plate promoting the transmission of collision‐related compressional stresses into the foreland since the middle Miocene. Nowadays, compression is still active and produces low‐magnitude earthquakes likely linked to NNE‐SSW to NE‐SW preexiting faults reactivated with reverse oblique‐slip kinematics. Seismicity is mostly concentrated around fault tips that are frequently curved in overstepping zones.
Unexpected seismicity has been detected in the past few years along the northern Guadiana Menor River (Guadalquivir foreland basin) at the northern boundary of the Betic Cordillera. Earthquake focal mechanisms evidence the activity of N‐S to NNE‐SSW sinistral faults in the basement. Yet continuous GPS (CGPS) data show a westward movement in both the Prebetic Arc and the eastern Guadalquivir basin infill, which disagrees with the strike‐slip faults. To more precisely describe the structure and evolution of the area, new Bouguer anomaly data from the southeastern basin combined with seismicity data, electric resistivity tomography profiles (ERT), and surface studies are provided. Given the soft consistency of the sedimentary infill in the area, surface evidence of faulting is scarce, limited to elongated channel and minor vertical faults affecting Quaternary sediments, where ERT profiles suggested the presence of faults. These results suggest that the Guadalquivir basin infill, the Prebetic Arc and the central Betic Cordillera move towards the west, independent from the Iberian crust, but indicating to some extent an upward propagation of the basement deformation. However, the basement is coupled with the Alboran Domain and undergoes NNW‐SSE Eurasia‐Nubia convergence and orthogonal extension. This scenario is suggestive of the initial stages of indentation tectonics, better developed in the eastern Betic Cordillera and the central Alboran Sea.