Upper Crustal Structure and Magmatism in Southwest Washington: Vp, Vs, and Vp/Vs Results From the iMUSH Active‐Source Seismic Experiment
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Kiser_et_al-2019-Journal_of_Ge ...
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Final Published Version
Affiliation
Univ Arizona, Dept GeosciIssue Date
2019-07-25Keywords
Mount StHelens
iMUSH
travel time tomography
Siletzia
Southern Washington Cascades Conductor
Indian Heaven Volcanic Heaven
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AMER GEOPHYSICAL UNIONCitation
Kiser, E., Levander, A., Zelt, C., Schmandt, B., & Hansen, S. (2019). Upper crustal structure and magmatism in southwest Washington: Vp,Vs, and Vp/Vs results from the iMUSH active‐source seismic experiment. Journal of Geophysical Research: Solid Earth, 124, 7067–7080. https://doi.org/10.1029/2018JB016203Rights
Copyright © 2019. American Geophysical Union. All Rights Reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
Structural details of the crust play an important role in controlling the distribution of volcanic activity in arc systems. In southwest Washington, several different regional structures associated with accretion and magmatism have been invoked to explain the broad distribution of Cascade volcanism in this region. In order to image these regional structures in the upper crust, Pg and Sg travel times from the imaging Magma Under St. Helens (iMUSH) active-source seismic experiment are inverted for V-p, V-s, and V-p/V-s models in the region surrounding Mount St. Helens. Several features of these models provide new insights into the regional structure of the upper crust. A large section of the Southern Washington Cascades Conductor is imaged as a low V-p/V-s anomaly that is inferred to represent a broad sedimentary/metasedimentary sequence that composes the upper crust in this region. The accreted terrane Siletzia is imaged west of Mount St. Helens as north/south trending high V-p and V-p/V-s bodies. The V-p/V-s model shows relatively high V-p/V-s regions near Mount St. Helens and the Indian Heaven Volcanic Field, which could be related to the presence of magmatic fluids. Separating these two volcanic regions below 6-km depth is a northeast trending series of high V-p and V-s bodies. These bodies have the same orientation as several volcanic/magmatic features at the surface, including Mount St. Helens and Mount Rainier, and it is argued that these high-velocity features are a regional-scale group of intrusive bodies associated with a crustal weak zone that focuses magma ascent.Note
6 month embargo; published online: 25 July 2019ISSN
2169-9313Version
Final published versionSponsors
National Science Foundation [EAR-1144455, EAR-1445937, EAR-1545750]ae974a485f413a2113503eed53cd6c53
10.1029/2018jb016203