Gestió d'una xarxa sísmica en temps real localitzada al Pirineu Oriental (La Cerdanya): relocalització hipocentral del període desembre 2019 - juny 2020 i anàlisis sismotectònic

Abstract

Seismicity in the Eastern Pyrenees has shown moderate and diffuse over time. Although, there is evidence of catastrophic historical earthquakes and some of the events in the last decade that have caused considerable damage. This work shows the feasibility to obtain seismic data of best quality in the temporary seismic network installed on Cerdanya Neogene basin. The network has recorded local events that are added to the permanent seismic networks of the ICGC, IGN and RéNaSS distributed region, for the period between December of 2019 and June 2020. Seismic data processing has been performed using the Seiscomp3 seismological software package. A cortical velocity model has been created to improve the accuracy of the location, adjusted to the geology of the Cerdanya basin and the region around it. The catalogue contains 641 seismic events and 251 quarry blasts. The results of the study show that the locations of earthquakes have higher resolution (with vertical errors as low 1 km) in the Cerdanya when including the temporary network as a result of a denser network in this area. Also, it shows that seismicity of Eastern Pyrenees is concentrated in the north and easternmore areas. The recorded data has allowed to discuss the seismotectonic of the Cerdanya, Selva and Fenollet areas, where 202, 158 and 54 earthquakes have been identified, respectively. The hypocentres are distributed in depth from to surface to a maximum of 16 km. In particular, two areas show lineaments that could be related to individual structures: At Meranges (Cerdanya), the events could be grouped in two to three fault planes (dipping NW and SE) perpendicular to Cerdanya fault. In Santa Coloma, (Selva), the network has recorded a seismic cluster (main event 4,2 magnitude) that seems to follow a SE dipping structure. As showed in this study, seismic data in larger periods of time using temporary network could be key for improving the seismotectonic knowledge in some target seismic regions, benefiting the seismic hazard evaluation.