Relocation of Seismicity in the Guadalentín Tectonic Valley, Eastern Betics Shear Zone (Southeast Iberia)

Abstract

The eastern Betics shear zone comprises one of the most seismically active areas in Iberia, due to the presence of large active faults loaded by the oblique convergence between Eurasia and Africa plates. We focus our study on the sector of the eastern Betic Cordillera affected by the Alhama de Murcia fault (AMF) and other nearby faults that are the source of large paleoseismic events and some damaging historical earthquakes. This study aims to give more accurate locations to the hypocenters in the region around these faults, using a model that accounts for lateral variations of P-wave velocity. This task was accomplished, developing a new 3D velocity crustal model of the region, by combining recent regional and local geological and geophysical data, such as geological mapping, gravimetry, seismic-wave tomography, and seismic exploration surveys. Afterward, as a preliminary test of performance, we compared the hypocenters obtained with this model against the ones computed with other 1D velocity models, using NonLinLoc with a seismic dataset of the highest possible quality (i.e., filtered by a minimum magnitude) in this area within the period January 2015–December 2018. Then, for comparing the reliability of the new 3D local model against a larger 3D regional model, we carried out a final relocation with all the earthquakes of the Spanish Seismic Catalog in the study area for the period April 2011–October 2019. New locations obtained with the local model, which show better clustering near active structures and lower epicentral uncertainty in comparison with the regional model, allow us to observe possible genetic relation between seismicity and specific faults after the inversion, in particular, the AMF.