Characterizing Sub-Seafloor Seismic Structure of the Alaska Peninsula Along the Alaska-Aleutian Subduction Zone

TitleCharacterizing Sub-Seafloor Seismic Structure of the Alaska Peninsula Along the Alaska-Aleutian Subduction Zone
Publication TypeJournal Article
Year of Publication2024
AuthorsZheng M, Sheehan AF, Liu C, Wu M, Ritzwoller MH
JournalJournal of Geophysical Research: Solid Earth
Volume129
Paginatione2024JB029862
KeywordsAlaska peninsula, seafloor compliance, sub-seafloor structure
Abstract

Abstract A shallow sub-seafloor seismic model that includes well-determined seismic velocities and clarifies sediment-crust discontinuities is needed to characterize the physical properties of marine sediments and the oceanic crust and to serve as a reference for deeper seismic modeling endeavors. This study estimates the seismic structure of marine sediments and the shallow oceanic crust of the Alaska-Aleutian subduction zone at the Alaska Peninsula, using data from the Alaska Amphibious Community Seismic Experiment (AACSE). We measure seafloor compliance and Ps converted wave delays from AACSE ocean-bottom seismometers (OBS) and seafloor pressure data and interpret these measurements using a joint Bayesian Monte Carlo inversion to produce a sub-seafloor S-wave velocity model beneath each available OBS station. The sediment thickness across the array varies considerably, ranging from about 50 m to 2.80 km, with the thickest sediment located in the continental slope. Lithological composition plays an important role in shaping the seismic properties of seafloor sediment. Deep-sea deposits on the incoming plate, which contain biogenic materials, tend to have reduced S-wave velocities, contrasting with the clay-rich sediments in the shallow continental shelf and continental slope. A difference in S-wave velocities is observed for upper oceanic crust formed at fast-rate (Shumagin) and intermediate-rate (Semidi) spreading centers. The reduced S-wave velocities in the Semidi crust may be caused by increased faulting and possible lithological variations, related to a previous period of intermediate-rate spreading.

DOI10.1029/2024JB029862

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