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Modeling Layered Anisotropy in the Alaska-Aleutians Subduction Zone

Description: 

A major limitation of shear wave splitting is its path-integrated nature. The most commonly used core-refracted teleseismic phases traverse thousands of kilometers from the core-mantle boundary to the receiver, complicating interpretation of the signal. Contributions from multiple layers of anisotropy can be determined using forward modeling. Yet these forward models often do not consider more than two layers of anisotropy, the effects of dipping layers, or the statistical robustness of the results.

We present multilayer shear wave splitting modeling along the Alaska-Aleutians Subduction Zone (AASZ). With an updated splitting catalog, we are able to identify six regions with sufficient density of splits to forward model. We model these splits with two- and three-layer cases, including with tectonically derived middle dipping layers. Based on our modeling and previous anisotropic studies using shear wave splitting and tomography, we ultimately choose a three layer model with a dipping middle layer with the axis of anisotropy oriented parallel to paleospreading. At five of the six regions, we identify a suite of models that is statistically better than a single-layer case. These models oftentimes differ from the “best-fitting” model, implying that only considering the model with the lowest misfit will provide an inaccurate representation of layered anisotropy. We also argue that the inclusion of tectonically-derived fabrics in these models is an important step, especially in regions such as subduction zones where these fabrics are well constrained.

Session: Anisotropy Across Scales - II

Type: Oral

Date: 5/3/2024

Presentation Time: 10:45 AM (local time)

Presenting Author: Andrew

Student Presenter: No

Invited Presentation: Yes

Authors