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

Abstract

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.

A Reciprocity‐Based Efficient Method for Improved Source Parameter Estimation of Submarine Earthquakes With Hybrid 3‐D Teleseismic Green's Functions

“…For example, expanding to global OTF events would advance our understanding of OTF earthquake mechanics (e.g., Boettcher & Jordan, 2004; Shi et al., 2022). It is also straightforward to use this computationally efficient SEM‐DSM code for modeling teleseismic waves from earthquakes at outer‐rise regions of subduction zones, where the associated hydration processes could have substantial impacts on deep Earth material recycling (Cai et al., 2018; Chen et al., 2022; Emry & Wiens, 2015), and in subducted zones, which could generate serious seismic hazards (Lay et al., 2019; Lay & Rhode, 2019; Wang & Yue, 2022).…”