Performance of an Impact-Based Earthquake Early Warning System in the Alboran Sea

Abstract This article presents the implementation and testing of a new P-wave shaking-forecast-based earthquake early warning system (EEWS) at the Ibero-Maghrebian region (IMR). The method integrates peak ground velocity (PGV) predictions derived from observed P-wave amplitudes with region-specific ground-motion prediction equations (GMPEs) to facilitate real-time mapping of the potential damage zone. We determined empirical relationships between PGV and P-wave peak amplitudes (in acceleration, velocity, and displacement) and magnitude, along with the development of a GMPE for Mw≥4 earthquakes in the IMR. These relationships are validated in the EEWS application using data from the 2016 Alboran Sea seismic series (Mw 5.0–6.4), which showed minimal discrepancies in origin time, epicenter location, and magnitude estimates compared to previous studies. A retrospective performance analysis for the Mw 6.4 mainshock indicated lead times of 14–62 s at a PGV threshold of 0.20 cm/s, with lead times increasing with distance. At a higher threshold of 0.60 cm/s, the lead time was 20 s for distances up to 170 km. The accuracy of impact predictions improved over time, with successful alerts rising from 72% to 90% as the final predictions were made. Despite some limitations due to focusing on moderate-magnitude earthquakes (Mw≤6.4), the EEWS method has proven effective for offshore events in areas with sparse instrumentation.