 Gravimetric data highlight the geometry of the sedimentary infill of the Granada Basin, which constitutes a half-graben tilted to the N-NE. Granada Basin´s high-angle normal faults might be linked at depth to an active low-angle extensional deformation zone. The active Granada Fault zone shows low magnitude seismicity and current average vertical rate that varies from 0.4 to 1.1 mm/yr.

The Gibraltar Arc includes the Betic and Rif Cordilleras surrounding the Alboran Sea; it is formed at the northwest–southeast Eurasia–Nubia convergent plate boundary in the westernmost Mediterranean. Since 2006, the Campo de Dalias GNSS network has monitored active tectonic deformation of the most seismically active area on the north coast of the Alboran Sea. Our results show that the residual deformation rates with respect to Eurasia range from 1.7 to 3.0 mm/year; roughly homogenous west-southwestward displacements of the northern sites occur, while the southern sites evidence irregular displacements towards the west and northwest. This deformation pattern supports simultaneous east-northeast–west-southwest extension, accommodated by normal and oblique faults, and north-northwest–south-southeast shortening that develops east-northeast–west-southwest folds. Moreover, the GNSS results point to dextral creep of the main northwest–southeast Balanegra Fault. These GNNS results thus reveal, for the first time, present-day interaction of the roll-back tectonics of the Rif–Gibraltar–Betic slab in the western part of the Gibraltar Arc with the indentation tectonics affecting the eastern and southern areas, providing new insights for improving tectonic models of arcuate orogens.

Fault barriers are key structures for studying seismic hazard in regions of intense brittle deformation. The interaction between fault sets affects their seismogenic behavior, if some of them act as barriers. The Granada Basin, in the Betic Cordillera, is a region affected by shallow brittle deformation, as it was the scenario for the recent Granada 2021 seismic sequence. This seismicity presented a swarm behavior at the beginning of the sequence, followed by mainshock‐aftershock features. Geological and gravity data presented here reveal that the basement is affected by two sets of NW‐SE and NE‐SW normal faults and intensely deformed by vertical NW‐SE joints. Improved relocation of the Granada 2021 seismicity reveals a confined chimney‐shape seismicity caused by the activity of a 2 km long NW‐SE normal fault segment. The confinement of the sequence is associated with the NE‐SW fault set acting as a barrier that restricts the rupture area, limiting the maximum magnitude, and favoring the recurrence of events with smaller magnitude. The chimney‐shape of the seismic sequence suggests that the deformation is propagated vertically to the surface, facilitated by preexisting fractures. The shallow extensional deformation during the uplift of the central Betic Cordillera drove the activity of the local structures obliquely to the regional extensional trends, as evidenced by the seismic sequence. This multidisciplinary study improves the knowledge on the origin of the Granada Basin and underlies the important role of preexisting fractures on fault segmentation and seismic propagation, decreasing the seismic potential of this area.

The coexistence of shortening and extensional tectonic regimes is a common feature in orogenic belts. The westernmost end of the Western Mediterranean is an area undergoing shortening related to the 5 mm/yr NNW‒SSE convergence of the Nubia and Eurasia Plates. In this region, the Central Betic Cordillera shows a regional ENE‒WSW extension. Here, we present GNSS‐derived geodetic data along a 170 km‐long transect orthogonal to the main active normal faults of the Central Betic Cordillera. Our data indicate that the total extension rate along the Central Betic Cordillera is 2.0 ± 0.3 mm/yr. Extension is accommodated in the eastern (0.8 ± 0.3 mm/yr in the Guadix‐Baza Basin) and western (1.3 ± 0.3 mm/yr in the Granada Basin) parts of the Central Betic Cordillera, while no extension is recorded in the central part of the study area. Moreover, our data permit us to quantify, for the first time, short‐term fault slip rates of the Granada Fault System, which is one of the main seismogenic sources of the Iberian Peninsula. We deduce a fault slip rate of ∼1.3 ± 0.3 mm/yr for the whole Granada Basin, with 0.9 ± 0.3 mm/yr being accommodated in the Granada Fault System and 0.4 ± 0.3 mm/yr being accommodated in the southwestern sector of the Granada Basin, where no active faults have been previously described at the surface. The heterogeneous extension in the Central Betic Cordillera could be accommodated by shallow high‐angle normal faults that merge with a detachment at depth. Part of the active extension could be derived from gravitational instability because of underlying over‐thickened crust.

The Betic Cordillera was formed by the collision between the Alboran Domain and the South Iberian paleomargin in the frame of the NW–SE convergent Eurasia–Nubia plate boundary. The central region is undergoing a heterogeneous extension that has not been adequately analysed. This comprehensive study addressed it by collecting structural geologic, seismologic, and geodetic data. The region west of the Sierra Nevada is deformed by the extensional system of the Granada Basin, which facilitates E–W to NE–SW extension. Moreover, the southern boundary of Sierra Nevada is affected by a remarkable N–S extension related to E–W normal to normal–dextral faults affecting the shallow crust. However, geologic and geodetic data suggest that the western and southwestern Granada Basin boundary constitutes a compressional front. These data lead to the proposal of an active extensional collapse from the uplifted Sierra Nevada region to the W–SW–S, over an extensional detachment. The collapse is determined by the uplift of the central Betics and the subsidence in the Alboran Basin due to an active subduction with rollback. Our results indicate that the central Betic Cordillera is a good example of ongoing extensional collapse in the general context of plate convergence, where crustal thickening and thinning simultaneously occur.