The July 14, 2025 Mw 5.3 earthquake in the NE Alboran Sea (Spain): insights into the causative source from seismic relocation and moment tensor analysis

On 14 July 2025, an Mw 5.3 earthquake occurred in the northeastern Alboran Sea, Spain. Its epicenter was close to the Eastern Betics Shear Zone, a region that has historically experienced major destructive earthquakes, including events with macroseismic intensity VIII–IX (EMS-98) in Vera (1,518), Alhama de Almería (1,522), and Dalías (1,804). However, in the area closest to the epicenter, offshore from the Almería coast, no previous earthquakes of this magnitude or greater have been recorded, and the nearest mapped active faults, the Carboneras Fault and the Palomares Fault, are both approximately 50 km away. To investigate the source responsible for this earthquake, we compute its seismic moment tensor and relocate the subsequent seismic sequence using a three-dimensional Earth model in a non-linear probabilistic approach and a double-difference relocation. Additionally, to better understand this offshore area, we apply the same methodology to study three similar recent seismic sequences along the Carboneras Fault in 2008, 2010, and 2012, west of the 2025 event. The mainshock moment tensor solution shows a strike-slip faulting mechanism consistent with the regional tectonics, and the relocated sequences form dense, elongated clusters, mainly following a NW–SE trend, perpendicular to the Carboneras Fault. The depth distribution shows that hypocenters in the 2025 seismic series are deeper, ranging from 5 to 20 km and slightly increasing to the northwest, compared with the previous sequences, whose hypocenters are mostly shallower (