Full waveform modeling and inversion of seismic attenuation and application to characterizing near-surface fractures at Susquehanna Shale Hills Critical Zone Observatory

地震学家经常使用地震波来研究地球内部。这是因为地震波的性质对地球的物理和化学状态非常敏感，从浅层到深层都是如此。该项目探索了这样一个特性，即地震衰减，它被认为是地球深度温度以及流体存在的直接指标。由于它的多用途，地球结构中这种属性的地图可以提高我们对地球内部工作方式的理解。该项目的主要目标是开发一种利用地震波成像地震衰减的方法。更广泛的影响包括宾夕法尼亚州立大学的一名博士后研究员的指导，以及科学界使用的新方法的开发。对地震波衰减的测量可能提供有关地球内部物理和化学状态的宝贵信息来源。地震全波形反演（FWI）作为一种很有前途的反演Q的测量工具，仍有几个关键问题需要研究：1)现有的分离振幅吸收和相位色散的分数阶非弹性波方程是否有利于FWI的发展；2)将显式Q嵌入分数阶非弹性波动方程，简化了梯度的计算；3)如何缓解FWI中速度与Q之间的串扰。为了解决这些问题，本项目将进行三项主要任务。首先，从新建立的参数化显式Q的分数阶非弹性波动方程出发，利用伴随态方法建立Q- fwi方法。其次，寻找适合多参数（速度和Q）的反演策略。第三，Q-FWI将使用合成近地表地质模型进行验证。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Seismologists often use seismic waves to study the Earth's interior. This is because seismic wave properties are very sensitive to the physical and chemical state of the Earth, from the shallow to the deep Earth. This project explores one such property, seismic attenuation, which is considered to be a direct indicator for temperature of the Earth with depth, as well as the presence of fluids. Because of its multi-purpose use, a map of this property in Earth structure can improve our understanding of how the Earth's interior works. The main goal of this project is to develop a method to image seismic attenuation using seismic waves. Broader impacts include the mentoring of a postdoctoral researcher at Penn State University and the development of new methods for the scientific community to use.Measurements of seismic wave attenuation potentially provide valuable source of information about the physical and chemical state of the Earth's interior. Seismic full waveform inversion (FWI) as a promising measurement tool for inverting Q still has several key issues to be investigated: 1) whether or not the existing fractional anelastic wave equation, that separates amplitude absorption and phase dispersion, can facilitate the development of FWI; 2) explicit Q embedded in fractional anelastic wave equations will simplify the computations of gradient; 3) how cross-talks between velocity and Q in FWI could be alleviated. To address these issues, this project will conduct three main tasks. First, starting from the newly developed fractional anelastic wave equation that parameterize an explicit Q, a Q-FWI method will be developed using adjoint-state approaches. Second, a suitable inversion strategy for multi-parameters (velocity and Q) will be sought. Third, the Q-FWI will be validated using synthetic near-surface geological models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.