23-11 Imaging the Alaskan Subduction Zone Using Love Wave Phase Velocity Tomography

Session: Subduction Zones and Their Volcanic Arcs: Initiation and Evolution, Structure, Metamorphism, Magmatism (Posters)

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The Alaska subduction zone is one of the most tectonically active zones in the world with variations in seismicity style along the trench. We present Love wave phase velocity tomography results from the Alaska Amphibious Community Seismic Experiment (AACSE) as well as stations within the area from the Transportable Array, the Alaska Volcano Observatory and other local networks. The land-ocean hybrid array provided good resolution on land as well as offshore, allowing us to focus the results on the subducting slab interactions with the North American Plate. Phase velocities in the Pacific Plate increase rapidly between 24s and 33s periods with a slower increase in velocities between 33s and 57s periods and finally, the velocity plateaus at periods above 57s. At periods below 33s, a low velocity zone is observed in the Pacific Plate within the offshore zone of the Shumagin Gap. The reduced velocities can be attributed to a higher degree of serpentinization in this area, which affects the seismicity and hinders large ruptures of the megathrust. At periods below 57s, the Pacific Plate shows consistently faster Love wave phase velocities than other areas in Alaska that reflect the thinner oceanic crust and high upper mantle velocities. On average, the continental shelf has higher velocities than all other areas, except for the Pacific Plate. This suggests that we are sampling the continental crust and subducting slab beneath the shelf, resulting in a combined elevated velocity on the shelf. Velocities in the volcanic arc are slower than in other regions at periods below 30s as well as above 57s, which reflect the velocity reduction from melt in the volcanic centers and melt generation in the mantle wedge. In much of the Alaska Range, at periods below 47s, the velocities are much slower than in other land locations, reflecting the thick crustal thickness of the mountain range.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

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