Velocity structure of the subducted Yakutat Terrane, Alaska: Insights from guided waves

Journal article

Dispersed P wave arrivals from intermediate-depth earthquakes in the Alaskan subduction zone provide insight into the low-velocity structure of the subducting oceanic crust. P wave arrivals from 41 earthquakes in the eastern section of the arc show significant guided wave dispersion, with high-frequency ( > 1 Hz) energy delayed by up to 2-3 s. We simulate this dispersion using a 2-D finite difference waveform propagation model, systematically varying both P wave velocity and low-velocity layer thickness parameters to find the lowest misfit between the observed and synthetic waveforms. We infer a 6 to 10 km thick low-velocity layer with a P wave velocity contrast of 7-15% with the overriding mantle, velocities which cannot be entirely accounted for by metamorphosed mid-ocean ridge basalt compositions. We postulate that this structure is the remnant of the subducted Yakutat terrane, significantly thinned at depth by metamorphism or delamination of material during subduction.

Authors: Coulson, S; Garth, T; Rietbrock, A

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Geophysical Union
• Journal: Geophysical Research Letters
• Volume: 45
• Issue: 8
• Pages: 3420-3428
• Publication date: 2018-04-16
• Acceptance date: 2018-03-28
• DOI: 10.1002/2017GL076583
• EISSN: 1944-8007
• ISSN: 0094-8276
• Keywords: Article in Press