Deployment of a local seismic network around the northern Guadiana Menor River (Betic Cordillera, Spain)

The Guadiana Menor River, included in the Guadalquivir foreland basin, at the northern border of the Betic Cordillera, has suffered in the last decade some low to moderate magnitude seismic series. For instance, the so called 2012-2013 Sabiote-Torreperogil seismic sequence, 1 to 5 km deep, being the biggest recorded event a m_bLg 3.9 earthquake, and the so called 2016-2018 Jódar-Peal de Becerro seismic series, less than 2 km and 9 to 13 km deep, 20 km southeast of the previous one, being a m_bLg 4.1 event the greatest recorded magnitude. In both cases, seismic series show focal mechanism solutions mostly with strike-slip and some dip-slip and NW-SE compression with no clear tectonic features at surface, due to the sedimentary infill. The Spanish Instituto Geográfico Nacional (IGN) national seismic network recorded in the last years, mainly in the region of the 2016-2018 seismic sequence, some low magnitude earthquakes, showing that the fault that hosted these events continues to be active.

This was the main reason to develop a little local seismic network in the region, designed with the aim to study this persistent seismicity in terms of locations and focal mechanism solutions when there could be available data. It is equipped with six triaxial broadband sensors specifically deployed for this purpose, and also sharing data coming from a near IGN seismic station in the region. The seven seismic stations present as uniform azimuthal distribution as possible around the seismicity, being the nearest station less than 5 km from the seismicity area, and the farthest about 30 km away. Anyway, the seismic network spatial distribution has been conditioned for the fact that they are not permanent housing stations, requiring electric power. Most of the seismic stations are recording data from September 2021.

Real-time records are shared with the Spanish IGN seismic network in order to improve regional locations. Until now, several low magnitude earthquakes, below the perceptibility level of the national seismic network, have been located. In addition, focal mechanisms have been computed for some low magnitude events (~ m_bLg 2.0), congruent with strike-slip solutions.