Along-Strike Variations of Alaska Subduction Zone Structure and Hydration Determined From Amphibious Seismic Data

Zongshan Li, Douglas A. Wiens, Weisen Shen, Donna J. Shillington

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

We develop a 3-D isotropic shear velocity model for the Alaska subduction zone using data from seafloor and land-based seismographs to investigate along-strike variations in structure. By applying ambient noise and teleseismic Helmholtz tomography, we derive Rayleigh wave group and phase velocity dispersion maps, then invert them for shear velocity structure using a Bayesian Monte Carlo algorithm. For land-based stations, we perform a joint inversion of receiver functions and dispersion curves. The forearc crust is relatively thick (35–42 km) and has reduced lower crustal velocities beneath the Kodiak and Semidi segments, which may promote higher seismic coupling. Bristol Bay Basin crust is relatively thin and has a high-velocity lower layer, suggesting a dense mafic lower crust emplaced by the rifting processes. The incoming plate shows low uppermost mantle velocities, indicating serpentinization. This hydration is more pronounced in the Shumagin segment, with greater velocity reduction extending to 18 ± 3 km depth, compared to the Semidi segment, showing smaller reductions extending to 14 ± 3 km depth. Our estimates of percent serpentinization from VS reduction and VP/VS are larger than those determined using VP reduction in prior studies, likely due to water in cracks affecting VS more than VP. Revised estimates of serpentinization show that more water subducts than previous studies, and that twice as much mantle water is subducted in the Shumagin segment compared to the Semidi segment. Together with estimates from other subduction zones, the results indicate a wide variation in subducted mantle water between different subduction segments.

Original languageEnglish (US)
Article numbere2023JB027800
JournalJournal of Geophysical Research: Solid Earth
Volume129
Issue number3
DOIs
StatePublished - Mar 2024

Keywords

  • Alaska subduction zone
  • along-strike variation
  • forearc crustal thickness
  • incoming plate hydration
  • seismic tomography

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)

Fingerprint

Dive into the research topics of 'Along-Strike Variations of Alaska Subduction Zone Structure and Hydration Determined From Amphibious Seismic Data'. Together they form a unique fingerprint.

Cite this