Synthetic Inversions for Anisotropic Structures using Wavefield Simulations and Adjoint Methods
Description:
Laboratory measurements confirm the presence of complex (low-symmetry) elasticity in a wide range of materials. The presence of anisotropy in the uppermost mantle is well established. In subduction settings, anisotropy is complex, with different elements—the subducting plate, the mantle wedge, and the crust—potentially having different forms of anisotropy. Seismic imaging problems generally offer non-unique solutions, due to extreme heterogeneity and sparse coverage of stations and source. The addition of parameters due to the consideration of anisotropy makes the problem even more challenging. Here, in preparation for real seismic imaging problems, we perform a series of synthetic tomographic inversions, whereby a synthetic target model is used to generate synthetic data for a given source-station geometry. An initial model, different from the target model, is used to generate initial synthetic seismograms. Through formal minimization between initial and target seismograms, we iteratively perturb and improve the initial model toward the target model. We consider different target model blocks, each having a predefined type of homogenous anisotropy, and we test their recovery with a source-station geometry designed to have good, yet realistic, coverage of the medium. We test the limits of recovery of these synthetic anisotropy models by changing: 1) the size of the anomaly, 2) the degree of symmetry of the anomaly, 3) the strength of anisotropy (angular distance from isotropy), 4) the density of station coverage, and 5) the portion of waveforms to use in the inversion. Our study prepares us for realistic synthetic inversions for complex anisotropic structures, which will guide efforts for performing adjoint tomography in the Alaska subduction zone.
Session: 3D Wavefield Simulations: From Seismic Imaging to Ground Motion Modelling [Poster Session]
Type: Poster
Date: 5/2/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Aakash
Student Presenter: Yes
Invited Presentation:
Authors
Aakash Gupta Presenting Author Corresponding Author agupta7@alaska.edu University of Alaska Fairbanks |
Bryant Chow bhchow@alaska.edu University of Alaska Fairbanks |
Carl Tape ctape@alaska.edu University of Alaska Fairbanks |
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Synthetic Inversions for Anisotropic Structures using Wavefield Simulations and Adjoint Methods
Session
3D Wavefield Simulations: From Seismic Imaging to Ground Motion Modelling