New insights on the crustal deformation in the Eastern Betics from densified GNSS data

Abstract

The Eastern Betic cordillera, southeastern Spain, is characterized by slow tectonic deformation rates and moderate seismicity. Great uncertainties persist regarding the precise kinematics of the main fault system within the region, the Eastern Betic Shear Zone (EBSZ). We present a new GNSS (Global Navigation Satellite System) velocity field in the Eastern Betics, including new episodic and continuous stations belonging to the GeoActiva network, as well as all available continuous stations in southern Iberia. We use this data to build kinematic models with elastic blocks, obtaining slip rates and locking ratios in the main faults of the EBSZ. Our model suggests that the central EBSZ is dominated by reverse and sinistral motion, accommodated by two fault branches closing the Guadalentín and Segura valleys. For the first time, we use geodetic data to quantify how slip is distributed between these branches in the central EBSZ: the Alhama de Murcia fault (western branch) accommodates up to 1.3 mm/yr sinistral and 0.6 mm/yr reverse slip, while the Palomares fault (eastern branch) is slower (0.5 mm/yr sinistral and 0.3 mm/yr reverse slip). Although slip rates are higher in the south Palomares and Carboneras faults, data scarcity limits their constraint. The deformation in the northern limit of the Eastern Betics appears to be distributed between the Jumilla and Crevillente faults. On a regional scale, our data suggest that the Nubia-Eurasia plate convergence is distributed radially from the Eastern Betics, consistent with the escape of multiple blocks driven by indentation and rollback tectonics in the Alboran Sea.