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-forecastbased 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 sat 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 overtime, 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.