An Evolutionary Shaking‐Forecast‐Based Earthquake Early Warning Method. Issue 4 (25th April 2023)

• Record Type: Journal Article
• Authors: Zollo, Aldo; Colombelli, Simona; Caruso, Alessandro; Elia, Luca
• Is Part Of: Earth and space science. Volume 10:Issue 4(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-04-25
• Subjects: earthquake early warning system -- earthquake rapid response -- impact‐base warning system; Space sciences -- Periodicals; Geophysics -- Periodicals; 500.5
• DOI: 10.1029/2022EA002657
• Languages: English
• ISSNs: 2333-5084

Abstract

Abstract: Here we propose a methodology for Earthquake Early Warning (EEW) able to issue the alert based on the real‐time estimation of the epicentral area where a peak ground Intensity measure is expected to exceed a user‐set ground shaking level. The method provides in output a P‐wave‐based, time‐evolutive "early" shake map. It combines the peak ground velocity predictions available from the observed P‐wave amplitudes and from the region‐specific ground motion prediction equation, using progressively updated estimates of earthquake location and magnitude. The P‐wave displacement, velocity and acceleration amplitudes are jointly measured on a progressively expanded P‐wave time window while the earthquake location and magnitude are evaluated using the first P‐arrival time and displacement amplitudes at near source stations. A retrospective analysis of the 2016, Mw 6.5 Central Italy earthquake records shows that depending on the network density and spatial source coverage, the method naturally accounts for effects related to the earthquake rupture directivity and spatial variability of strong ground motion related to crustal wave propagation and site amplification. Within 1.5 s from the first alert (5.15 s after the origin time), the simulated performance of the system in predicting the event ground shaking is very high: in the 40 km‐radius area that suffered an Intensity MCS VIII–IX, 41 over 42 strong‐motion instrumented sites would have been successfully alerted, with only one false alarm. Even considering the calculated blind‐zone of 15 km radius, a 15–55 km wide annular area would have received the alert 2–14.5 s before the occurrence of the strong ground shaking. The proposed EEW method evolves with time in a way that it minimizes the missed alarms while increasing successful alarms and to a lesser extent false alarms, so it is necessary for the end‐user to accept these possibilities and account for them in a probabilistic decision scheme depending on the specific safety actuation measure to be undertaken in real‐time. Plain Language Summary: Only few seconds pass between an earthquake rupture starting and seismic waves causing disastrous effect on populations and buildings. Earthquake Early Warning (EEW) systems are advanced seismic monitoring infrastructures aimed to benefit of this delay by triggering alerts and pilot safety actions that may mitigate losses. Here we propose a new method that issues the alert based on the real‐time tracing of the area where the strong motion is predicted to exceed a user‐set threshold. The predictions are derived from the early signal amplitudes radiated from the earthquake source using data‐driven relations. A retrospective study of the 2016, Mw 6.5 Central Italy earthquake shows that the method is high performing in rapidly delineating the potential damage zone, naturally accounting for the spatial variability of strong ground motion related to source, path and site effects. Five seconds after the origin time the system predicts the 40 km‐radius area that suffered an MCS Intensity VIII‐IX with almost all strong‐motion sites that would have been successfully alerted. Our time‐evolutive EEW method mitigates losses for false‐alert‐tolerant users, setting the threshold and alert times based on their specific safety actions thus averaging between the system quickness in alerting and in the shaking predictions accuracy. Key Points: A shaking‐forecast‐based earthquake early warning system issuing the alert based on the real‐time tracing of the potential damage zone (PDZ) It naturally accounts for the complex source effects and spatial variability of strong motion related to path and site effects The method playback shows to be high performing in rapidly delineating the PDZ of the 2016 Mw 6.5 Central Italy earthquake