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Date Permissions Signed

2-23-2018

Date of Award

Spring 2008

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Crider, Juliet G.

Second Advisor

Caplan-Auerbach, Jacqueline

Third Advisor

Stelling, Peter L.

Abstract

Surface deformation studies at active volcanoes are used to detect changes to magmatic source regions beneath the volcano. At Mount Baker, Washington, continued elevated gas (CO2 and H2S) and heat flux from fumaroles in Sherman Crater indicate the presence of a degassing magma reservoir. Campaign geographic positioning system surveys in 2006 and 2007 provide slope distance measurements of all 19 trilateration lines on Mount Baker. These data are compared with previous slope distance measurements acquired in 1981 and 1983 with electronic distance measurement. The results indicate that surface deformation has occurred on Mount Baker during the last quarter century. Slope distances have predominantly shortened around the edifice at rates of less than 2 mm/yr. The greatest slope length change detected (HDLY-RSVT) is -17 ± 4 ppm on the northern flank of the volcano. A nonlinear least-squares regression fits a uniform surface strain-rate model to the weighted slope change data. The strain model results indicate contractional strain accumulation on Mount Baker with an areal dilation rate of -420 ± 140 nanostrain/yr. The observed strain-rate is distinctly different, by at least an order of magnitude, than the expected regional secular strain-rate from tectonic sources.

Elastic dislocation models are used to invert for the location, and strength of a point source at depth. The inversion uses a discrete grid search to find the global minimum of the residuals from a nonlinear least squares algorithm. The optimal model predicts a volume change of -11 x 106 m3, located 1500 meters east-northeast of the summit at a depth of 5.4 km (MSL). However, the global minimum in not well defined, resulting in a wide range of suitable source parameters. The model can account for much of the deformation detected, indicating that a spherical source model is appropriate, at least to a first order, for modeling physical changes to the magmatic or hydrothermal system at Mount Baker. These results suggest that the magmatic and hydrothermal system at Mount Baker has depressurized, likely from the combined result of cooling, mass loss, and/or densification, since 1981. This study also provides a new baseline for precise geodetic study of ongoing quiescent degassing at Mount Baker.

Type

Text

Keywords

Surface deformation, Mount Baker volcano

DOI

https://doi.org/10.25710/42w2-4c78

Publisher

Western Washington University

OCLC Number

1033605099

Comments

Additional files are available on a CD accompanying the hard copy of the thesis, call number: LD5778.9 H6895.

Subject – LCSH

Subsidences (Earth movements)--Washington (State)--Baker, Mount

Geographic Coverage

Baker, Mount (Wash.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

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