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Resolving Shallow Moment Releases of Megathrust Earthquakes by Empirical Green’s Function‐Based Inversions: A New Approach for Tsunami Warning

Tsunamis are secondary hazards generated by megathrust earthquakes, which are commonly related to coseismic slips occurring at shallow depths. Various methods were proposed to quickly predict tsunami excitations, while these methods mostly require specific observations or modeling techniques, which limits their application to global subduction zones. In this study, we propose an inversion technique that utilizes the water‐reverberation phases in teleseismic P coda waves to discriminate shallow and deep slips and adopts teleseismic empirical Green’s functions (EGFs) to enable rapid inversions. We developed an EGF extraction and interpolation method to construct Green’s functions. We apply this algorithm to seven megathrust earthquakes, which have been well studied and identified with or without significant shallow slips. In comparison with inversions performed with theoretical Green’s functions, the EGF‐based inversion technique is more effective in discriminating these two types of earthquakes. We propose a threshold to evaluate the percentage of shallow moment releases and found that the EGF‐based inversion result resembles that of joint inversion results. We also analyze the possibility to apply the EGF‐based inversion technique for tsunami warning purposes and infer that it serves as a promising algorithm to enable efficient tsunami early warning.