Refining Splitting Intensity Measurements of Shear Wave Splitting for Multi-Layer Anisotropy
Description:
The presence of seismic anisotropy within the Earth’s upper mantle is well-known and observed. Methods for measuring azimuthal anisotropy through shear wave splitting (Silver & Chan 1991, Vinnik et al. 1989) are proven to be effective, assuming a single layer of anisotropy with horizontal symmetry. However, these methods become less reliable when applied to regions of the Earth with more than one anisotropic layer. Results from these methods in the southwest Pacific imply non-orthogonal polarization directions, indicative of multi-layer anisotropy. The mentioned methodologies can produce multi-layer anisotropy measurements, but the resolution is highly dependent on azimuthal coverage and seismic data quality. Splitting Intensity (SI) is a robust method to measure azimuthal anisotropy from lower-quality data (Chevrot 2000), but it is mainly applied to single layer anisotropy.
Based on previously published theoretical expressions (Romanowicz & Yuan 2011), SI can be calculated from multiple layers of anisotropy. The focus of this study is to develop a robust measurement process for shear wave splitting in complex anisotropic media, incorporating the multi-layer expression of SI to solve for station-average anisotropic measurements. A double grid search method is applied to obtain splitting parameters from seismic data. Preliminary results of SI from stations inferred to have multi-layer anisotropy correlate with results presented with the theoretical expressions. Further development is required to refine the SI results obtained from this continually improving method. Results from this finer-constrained measurement process will be contributed as constraints for azimuthal anisotropy full waveform tomography of the southwest Pacific upper mantle and transition zone.
Session: Anisotropy Across Scales [Poster Session]
Type: Poster
Date: 5/3/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Nicolas
Student Presenter: Yes
Invited Presentation:
Authors
Nicolas Valencia Presenting Author Corresponding Author nicolasv03@berkeley.edu University of California, Berkeley |
Utpal Kumar utpalkumar@berkeley.edu University of California, Berkeley |
Dorian Soergel d.soergel@berkeley.edu University of California, Berkeley |
Barbara Romanowicz barbarar@berkeley.edu University of California, Berkeley |
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Refining Splitting Intensity Measurements of Shear Wave Splitting for Multi-Layer Anisotropy
Session
Anisotropy Across Scales