Relocated hypocenters of the February 2026 seismicity in SW Betic Cordillera (South Spain)

We have relocated the seismicity occurred in the vicinity of Grazalema and Líbar ranges within the Western Betic Cordillera (South Spain) during February 2026 through a two-step relocation, absolute and relative, by means of a nonlinear probabilistic approach with a regional 3D velocity model and double-difference algorithm with a 1ocal 1D velocity model, respectively. We provide two XLSX files containing the following information: - README: description of the relocation procedure and programs used, files and references.- stations: stations used for the hypocentral relocation- events: initial earthquake catalog (before each relocation)- control files: parameters used for the configuration of the control file of each program - relocated hypocenters: final hypocentral parameters of the relocated earthquake dataset Data: Data corresponds to good-quality waveforms from BB seismic stations and P- and S-wave arrivals from the IGN catalog (doi:10.7419/162.03.2022) recorded by permanent and temporary broadband (BB) and strong-motion stations. Main seismic networks: - Spanish Digital Seismic Network (ES, doi:10.7914/SN/ES). Data from 3 temporary velocity stations installed in the epicentral region are available since 8 February 2026 - Andalusian Institute of Geophysics and Earthquake Disaster Prevention network (IG) (https://iagpds.ugr.es, last accessed February 2026) - Western Mediterranean network (WM, doi:10.14470/JZ581150) - Morocco Seismic Network from the Institut National de Géophysique, Rabat (CNRST) (MO) - Portuguese National Seismic Network (PM, doi:10.7914/SN/PM) Earthquake dataset: We relocated a subset of M>=1.5 earthquakes recorded in the area (36.2ºN-36.9ºN, 5.7ºW-5.1ºW) during the period 2026.02.03 - 2026.02.28, using all of the available seismic data. We selected M>=1.5 events to ensure a representative sample of the seismicity, with well-constrained earthquakes, taking into account the magnitude of completeness for this seismic sequence. Methodology: We performed a first absolute hypocentral location with a probabilistic non-linear approach and a regional 3D velocity model, and a second relative relocation based on double differences with a local 1D velocity model. - Absolute relocation: we applied NonLinLoc (NLL) location algorithm (Lomax et al., 2000; Lomax et al., 2014) to estimate the maximum likelihood hypocenter and posterior probability density function (PDF) of each event by means of a nonlinear global search in a 3D space. We used a regional 3D P-wave velocity model for the Alboran-Betic-Rif region (El Moudnib et al., 2015), for travel-time calculation to account for propagation effects in heterogeneous media. - Relative relocation: we applied HypoDD double-difference algorithm (Waldhauser and Ellsworth, 2000; Waldhauser, 2001) to refine the events relative positions and earthquake clustering. We used a local 1D P-wave velocity model obtained as a simplified mean velocity-depth profile derived from the 3D velocity grid from El Moudnib et al. (2015) for the epicentral area. A shallow low-velocity layer was added to the 1D model to prevent too much airquakes (near-surface earthquakes that are located above the surface after relocation) during the iteration process in hypoDD. References: - El Moudnib, L., Villaseñor, A., Harnafi, M., Gallart, J., Pazos, A., Serrano, I., et al. (2015). Crustal structure of the Betic–Rif system, western Mediterranean, from local earthquake tomography. Tectonophysics 643, 94–105. doi:10.1016/j.tecto.2014. 12.015 - Lomax, A., Virieux, J., Volant, P., and Berge-Thierry, C. (2000). “Probabilistic earthquake location in 3D and layered models,” in Advances in seismic event location. Modern approaches in geophysics Editors C. H. Thurber, and N. Rabinowitz 18 (Dordrecht: Springer). doi:10.1007/978-94-015-9536-0_5 - Lomax, A., Michelini, A., and Curtis, A. (2014). “Earthquake location, direct, global search methods,” in Encyclopedia of complexity and systems science. Editor R. Meyers (New York: Springer), 1–33. doi:10.1007/978-3-642-27737-5_150-2 - Waldhauser, F. (2001). HypoDD-A program to compute double-difference hypocenter locations. U.S. Geol. Surv. 113. doi:10.3133/ofr01113 - Waldhauser, F., and Ellsworth, W. L. (2000). A double-difference earthquake location algorithm: method and application to the Northern Hayward fault, California. Bull. Seismol. Soc. Am. 90 (6), 1353–1368. doi:10.1785/0120000006