Three-Dimensional Teleseismic Elastic Reverse-Time Migration With Deconvolution Imaging Condition and Its Application to Southwest Japan

We have developed a novel deconvolution-based reverse time migration method to image lithospheric structures using teleseismic data recorded by dense seismic arrays. Unlike traditional approaches that rely on the retrieval of Green's functions (or receiver functions), the new method directly utilizes the recorded three-component (3-C) seismic waveforms to reconstruct subsurface wavefields, which has the advantage of avoiding the estimation and removal of source time function. Importantly, it enables the asymptotic estimation of P-to-S transmission conversion coefficients at the elastic discontinuities and enhances resolving power for the fine-scale heterogeneities. Taking these improvements, we have obtained a full three-dimensional (3-D) high-resolution image of the subduction zone beneath southwest Japan. This image provides a comprehensive configuration of the severely deformed subducting plate beneath the Kii Channel and Kinki Peninsula. Wave equations based seismic imaging method theoretically possesses the most effective capacity for characterizing crustal and upper mantle strong laterally heterogeneous structures. However, its advantages have not been well manifested in the imaging of lithospheric structures, primarily due to the uncertainties introduced by the laborious data preprocessing to remove the complex source-side effects associated with each earthquake event. To address these uncertainties, we propose a novel method to automatically eliminate source side effects by introducing a deconvolution imaging condition. This enables the direct use of three-component seismic records only requiring some fundamental preprocessing, such as retrending, remeaning, tapering, and band-pass filtering, to image the Earth's interior structures. Accordingly, the first attempt of full three-dimensional elastic imaging beneath southwest Japan is intriguing, and unveils more detailed structures of the subduction zones compared to previous studies. Deconvolution imaging condition is proposed for elastic reverse-time migration of teleseismic waveforms with minimal data preconditioning Complex influence of source time function and long-distance propagation of the incident wavefield is effectively handled Three-dimensional elastic reverse time migration image beneath southwest Japan reveals more detailed structures of the Philipine Sea plate