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The Wave Gradiometry Method: Theory and Applications for Imaging 3D Velocity, Anisotropy and Attenuation

Description: 

The Wave Gradiometry Method (WGM) has emerged as a powerful multipurpose tool for extracting strain and rotation tensors, identifying phases, and, most importantly, imaging the near-surface or deep structure (Langston, 2007). The WGM measures the spatial gradients of the wavefield within a subarray to extract four major attributes: phase velocity, wave directionality, amplitude perturbation, and radiation pattern.

An azimuth-dependent dispersion curve inversion (ADDCI, Liang et al., 2020) is applied in conjunction with the WGM method to extract 3D shear wave velocity and 3D azimuthal anisotropy. Amplitude perturbation accounts for geometrical spreading relative to propagation distance, intrinsic attenuation, and wave scattering within the medium. By eliminating the effects of scattering and geometrical spreading, the dispersion curve of attenuation is obtained, allowing for the determination of the medium's 3D attenuation properties.

In this study, we review the theoretical foundations, technical developments, and major applications of the WGM, and compare it with other major array-based imaging methods. Although the WGM can be applied to arrays of various scales, our focus is on its applications to large-scale arrays, such as the USARRAY (with an average spacing of 70 km) and CHINARRAY (with an average spacing of 35 km). We will compare our results with those from other techniques to highlight the advantages and disadvantages of the WGM.

References：

Langston, C. A. (2007). Wave gradiometry in two dimensions. Bulletin of the Seismological Society of America, 97(2), 401–416. https://doi.org/10.1785/0120060138

Liang, C., Cao, F., Liu, Z., & Chang, Y. (2023). A review of the wave gradiometry method for seismic imaging. Earthquake Science, 36(3), 254-281. https://doi.org/10.1016/j.eqs.2023.04.002

Liang, C., Liu, Z., Hua, Q., Wang, L., Jiang, N., & Wu, J. (2020). The 3D seismic azimuthal anisotropies and velocities in the eastern Tibetan Plateau extracted by an azimuth‐dependent dispersion curve inversion method. Tectonics, 39, e2019TC005747. https://doi.org/10.1029/2019TC005747

Session: Earth’s Structure from the Crust to the Core - I

Type: Oral

Date: 4/16/2025

Presentation Time: 08:45 AM (local time)

Presenting Author: Chuntao

Student Presenter: No

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