How Fast Can We Reliably Estimate the Magnitude of Subduction Earthquakes?

Fast and reliable characterization of earthquakes can provide vital information to the population, even reducing the effects of strong shaking produced by them. In this study, we explore the minimum time required to estimate the magnitude for subduction earthquakes. Using traditional P wave earthquake early warning parameters and considering a progressively increasing time window, we are able to estimate magnitude for subduction earthquakes ~30 s from the origin time (with an average residual of 0.01 ± 0.28). However, estimations for larger events (Mw ≥ 7.5) present larger errors (average residual of −0.70 ± 0.30). We complement our data with Global Navigational Satellite System observations for these events, enabling magnitude estimations ~70 s from the origin time (average residual of −0.42 ± 0.41). We propose that rapid estimations of magnitude should consider, initially, P waves in a progressively increasing time window, and complemented with GNSS data, for large events