Velocity structure of the subducted Yakutat Terrane, Alaska: Insights from guided waves
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-frequ...
| Published in: | Geophysical Research Letters |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | unknown |
| Published: |
American Geophysical Union
2018
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| Subjects: | |
| Online Access: | https://doi.org/10.1002/2017GL076583 https://ora.ox.ac.uk/objects/uuid:a04cbd57-a5ae-46be-9325-517f1582ea81 |
| Summary: | 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. |
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