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Depth-Dependent Seismic Azimuthal Anisotropy Beneath the Aleutian Subduction Zone and the Juan De Fuca-Gorda Plates

Description: 

Benefiting from the deployment of ocean-bottom seismometer arrays in the Aleutian subduction zone (Alaska Amphibious Community Seismic Experiment (AACSE)) and the Juan de Fuca-Gorda plates (Cascadia Initiative (CI)), researchers have constructed high-resolution surface wave dispersion databases (e.g., Zhang, et al., 2021; Liu et al., 2022). Based on the Rayleigh wave phase speed azimuthal anisotropy databases from these two regions, we construct depth-dependent azimuthal anisotropy models for both the crust and uppermost mantle beneath the Aleutian subduction zone and the Juan de Fuca-Gorda plates.

These models of depth-dependent seismic anisotropy reveal distinct tectonic features of the subduction zone forearc and the young oceanic plate. In the forearc region of the Aleutian subduction zone, we observe a correlation between the along-strike variation in fast directions above the slab and the spatial changes in the orientation of local faults. Deeper within the subducted slab, we observe a trench-perpendicular pattern of anisotropy fast directions, suggesting the existence of fossil anisotropy. In contrast, on the Juan de Fuca-Gorda plates, we find that paleo-spreading directions may account for the anisotropy fast directions in most of the study region. Additionally, the dominant fast directions in the asthenosphere appear to be influenced by mantle flow, which is partially reflected in the absolute plate motion directions.

Session: Anisotropy Across Scales - II

Type: Oral

Date: 5/3/2024

Presentation Time: 11:00 AM (local time)

Presenting Author: Chuanming

Student Presenter: No

Invited Presentation: 

Authors