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A Possible Slab Window Along the Alaska Subduction Zone Imaged by Full Wave Ambient Noise Tomography

Along-strike heterogeneities of subduction zones have been observed globally with variable behaviors in seismicity, locking fraction, slab dip, and volcanism. The Alaska subduction zone is an ideal natural laboratory to study the processes controlling the along-strike variability of subduction systems. Previous studies have demonstrated differences in slab dip, megathrust seismicity, seismic anisotropy, plate interface locking fraction, and variations of slab hydration partly related to changes in oceanic plate fabrics. However, the relationship between these observations and the 3-D structural segmentation remains poorly constrained. Here we use full-wave ambient noise tomography to generate a 3-D shear-wave velocity model of the Alaska subduction zone in the Alaska Amphibious Community Seismic Experiment footprint along the Alaska peninsula. Our velocity model reveals strong variations in the geometry and velocity of the subducting Pacific slab. Low-velocity anomalies are present in regions of active volcanism and sediment subduction while fast-velocity anomalies are observed in the subducting slab. At mantle depths, low-velocity anomalies correlate with the projected changes in plate fabrics and the gap of intermediate-depth earthquakes, indicative of a potential slab window. Our findings suggest that, at the intersection of two plate fabrics, the slab might be relatively weak, which may facilitate tearing of the slab, allowing the sub-slab asthenosphere to flow through.

Session: Structure and Behavior of the Alaska-Aleutian Subduction Zone - IV

Type: Oral

Room: Tikahtnu Ballroom A

Date: 5/3/2024

Presentation Time: 05:00 PM (local time)

Presenting Author: Vincent Sassard

Student Presenter: Yes

Additional Authors