Attenuation and scattering tomography of the deep plumbing system of Mount St. Helens

Journal of Geophysical Research B: Solid Earth
By: , and 

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Abstract

We present a combined 3-D P wave attenuation, 2-D S coda attenuation, and 3-D S coda scattering tomography model of fluid pathways, feeding systems, and sediments below Mount St. Helens (MSH) volcano between depths of 0 and 18 km. High-scattering and high-attenuation shallow anomalies are indicative of magma and fluid-rich zones within and below the volcanic edifice down to 6 km depth, where a high-scattering body outlines the top of deeper aseismic velocity anomalies. Both the volcanic edifice and these structures induce a combination of strong scattering and attenuation on any seismic wavefield, particularly those recorded on the northern and eastern flanks of the volcanic cone. North of the cone between depths of 0 and 10 km, a low-velocity, high-scattering, and high-attenuation north-south trending trough is attributed to thick piles of Tertiary marine sediments within the St. Helens Seismic Zone. A laterally extended 3-D scattering contrast at depths of 10 to 14 km is related to the boundary between upper and lower crust and caused in our interpretation by the large-scale interaction of the Siletz terrane with the Cascade arc crust. This contrast presents a low-scattering, 4–6 km2 “hole” under the northeastern flank of the volcano. We infer that this section represents the main path of magma ascent from depths greater than 6 km at MSH, with a small north-east shift in the lower plumbing system of the volcano. We conclude that combinations of different nonstandard tomographic methods, leading toward full-waveform tomography, represent the future of seismic volcano imaging.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Attenuation and scattering tomography of the deep plumbing system of Mount St. Helens
Series title Journal of Geophysical Research B: Solid Earth
DOI 10.1002/2014JB011372
Volume 119
Issue 11
Year Published 2014
Language English
Publisher American Geophysical Union
Publisher location Richmond, VA
Contributing office(s) Volcano Science Center, Volcano Hazards Program
Description 16 p.
First page 8223
Last page 8238
Country United States
State Washington
County Skamania
Other Geospatial Mount St. Helens
Online Only (Y/N) N
Additional Online Files (Y/N) N