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Abstract

The current tsunami early warning systems usually issue alarms once large undersea earthquakes are detected, inevitably resulting in false warnings since there are no deterministic scaling relations between earthquake size and tsunami potential. In this study, we attemp to characterize tsunami potential more precisely to avoid uncessary alarms by analyzing both the co-seismic displacement waveforms (CDWs) and ionospheric disturbances (CIDs) as detected by high-rate Global Navigation Satellite System (GNSS) observations. We examined CDWs and CIDs of three megathrusts including the 2014 Mw 8.2 Iquique, the 2015 Mw 8.3 Illapel, and the recent 2021 Mw 8.2 Alaska events. We found that CDWs generated by the 2021 Mw 8.2 Alaska event indicating ruptures far away from the trench and CIDs near the epicenter event were significantly weaker than those of the two Chilean events, despite having similar earthquake magnitudes. Furthermore, the propagation direction of CIDs from the Mw 8.2 Alaska earthquake also confirmed slips toward the deeper seismogenic zone, consistent with CDWs infer and both implied less seafloor uplift and hazardous flooding. Our work sheds light on incorporating both GNSS-based CDWs and CIDs for more trustworthy tsunami warning systems.