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

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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.