Adjoint Attenuation Tomography of Sichuan–Yunnan Region

Abstract

AbstractWe use seismic waveform adjoint tomography to constrain the shear-wave attenuation models of the crust and upper mantle in Sichuan–Yunnan region of China. On the base of 3D velocity model with high accuracy by the previous work, we use the adjoint approach to efficiently construct the anelastic structures. Spectral element method with graphic processing unit acceleration is implemented in our work. We use an envelope-based misfit function and develop a mini-batch gradient descent algorithm for model update. We have applied the adjoint tomography algorithms to 41 seismic events, including 1911 high-quality three-component displacement seismic records from 2009 and 2017 in Sichuan–Yunnan region. Synthetic tests show that the attenuation model is well resolved. The generated shear-wave attenuation model reveals detailed structural characteristics of the upper mantle in Sichuan–Yunnan region. Some notable features are observed, such as an obvious strong-attenuation zone in northern Yunnan, which provides evidence for the existence of high-attenuation middle and lower crustal channels.