Seismic imaging of the Alaska Subduction Zone: implications for slab geometry and volcanism
File(s)
Author(s)
Martin-Short, Robert
Allen, Richard
Bastow, Ian
Porritt, Robert
Miller, Meghan
Type
Journal Article
Abstract
Alaska has been a site of subduction and terrane accretion since the mid‐Jurassic. The area features abundant seismicity, active volcanism, rapid uplift, and broad intraplate deformation, all associated with subduction of the Pacific plate beneath North America. The juxtaposition of a slab edge with subducted, overthickened crust of the Yakutat terrane beneath central Alaska is associated with many enigmatic volcanic features. The causes of the Denali Volcanic Gap, a 400‐km‐long zone of volcanic quiescence west of the slab edge, are debated. Furthermore, the Wrangell Volcanic Field, southeast of the volcanic gap, also has an unexplained relationship with subduction. To address these issues, we present a joint ambient noise, earthquake‐based surface wave, and P‐S receiver function tomography model of Alaska, along with a teleseismic S wave velocity model. We compare the crust and mantle structure between the volcanic and nonvolcanic regions, across the eastern edge of the slab and between models. Low crustal velocities correspond to sedimentary basins, and several terrane boundaries are marked by changes in Moho depth. The continental lithosphere directly beneath the Denali Volcanic Gap is thicker than in the adjacent volcanic region. We suggest that shallow subduction here has cooled the mantle wedge, allowing the formation of thick lithosphere by the prevention of hot asthenosphere from reaching depths where it can interact with fluids released from the slab and promote volcanism. There is no evidence for subducted material east of the edge of the Yakutat terrane, implying the Wrangell Volcanic Field formed directly above a slab edge.
Date Issued
2018-12-10
Date Acceptance
2018-10-11
Citation
Geochemistry, Geophysics, Geosystems, 2018, 19 (11), pp.4541-4560
ISSN
1525-2027
Publisher
American Geophysical Union
Start Page
4541
End Page
4560
Journal / Book Title
Geochemistry, Geophysics, Geosystems
Volume
19
Issue
11
Copyright Statement
©2018. American Geophysical Union. All Rights Reserved. This is the accepted version of the following articl, which has been published in final form at https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GC007962
Sponsor
The Leverhulme Trust
Grant Number
RPG-2013-332
Subjects
Science & Technology
Physical Sciences
Geochemistry & Geophysics
tomography
subduction
Alaska
SURFACE-WAVE DISPERSION
AMBIENT-NOISE
JOINT INVERSION
TECTONIC DEVELOPMENT
VELOCITY STRUCTURE
RECEIVER FUNCTIONS
CRUSTAL THICKNESS
YAKUTAT TERRANE
UPPER-MANTLE
BENEATH
04 Earth Sciences
02 Physical Sciences
Date Publish Online
2018-11-21