Four Years of Earthquake Early Warning in Southern Iberia: 2016–2019

The performance of an EEWS for southern Iberia during the period of 2016-2019 is analyzed. The software PRESTo (PRobabilistic and Evolutionary early warning SysTem; University of Naples Federico II, Italy) operating at the Universidad Complutense de Madrid has detected 728 events with good epicentral location and origin time estimations. The main differences between PRESTo’s estimates and those obtained by the Instituto Geografico Nacional are discussed, and improvements are proposed to decrease the time needed to issue the alert and avoid the false alerts (19 events over a total of 728 events). The magnitude is the parameters with more greater differences between the PRESTo and Instituto Geografico Nacional (IGN) solutions. To solve this problem, several relationships have been tested, and a modification to those that currently use PRESTo is proposed. The performance of PRESTo during the 2020-2021 Granada swarm is analyzed. The hypocentral locations for the three largest earthquakes are in good agreement with that of the IGN, but there are some differences in their magnitude estimations. The first warnings are obtained 17, 25 and 41 s after the origin time. This study shows that the actual PRESTo EEWS configured for southern Iberia generates effective warnings despite the low seismicity rate in this region. To decrease the warning time, the geometry and density of the seismic network must be improved together with the use of 3D Earth models and on-site system approaches.