Physical Sciences and Mathematics Commons^™

Evaluating The Sensitivity Of Crustal Deformation To Bedrock Hydrology In A Mountain Watershed, Brett J. Oliver

Graduate Student Theses, Dissertations, & Professional Papers

We evaluate the sensitivity of Earth's elastic deformation to groundwater hydraulic diffusivity using coupled groundwater and elastic deformation models. Seasonal changes in terrestrial water storage cause deformation to the Earth’s crust and deeper interior that is within the observational capacity of GPS instruments. We couple finite difference groundwater simulations with geodetic forward models of crustal displacement to investigate the ability of geodetic deformation to constrain bedrock hydrologic properties. We use MODFLOW-2005 to simulate seasonal changes in groundwater flow and storage, and then use the LoadDef elastic deformation model to forward model surface displacement caused by the change in terrestrial water …

Investigating Elastic Deformation Induced By Surface Loads On Planetary Bodies, Ashlesha Khatiwada, Hilary Martens, Donald F. Argus

Graduate Student Theses, Dissertations, & Professional Papers

Planetary bodies, including the Earth, deform when there is a redistribution of surface load. In this thesis, I conduct three independent projects related to surface loading, two of which investigate methods related to the modeling of surface loading and one which seeks to catalog the displacement responses of other planetary bodies to a surface load.

The first project aims to compare four methods for modeling the elastic loading response of the Earth: a homogeneous, non-gravitating, half-space method; a homogeneous, gravitating, spherical method; a homogeneous, non-gravitating spherical method; and a radially stratified gravitating spherical method. Many studies have focused on computing …

1-D Crustal Seismic Velocity Models For West-Central And Western Montana, Courtenay Duzet

Graduate Student Theses, Dissertations, & Professional Papers

In seismically active areas with infrequent, large-magnitude earthquakes, high-quality seismic data are critical for determining high-resolution, accurate seismic velocity models. Here, we present a new local-scale seismic velocity model for the crust in west-central Montana as well as a new regional-scale seismic velocity model for the crust and upper mantle across broader western Montana. The new models are constrained by phase arrivals from several passive seismic networks, including the University of Montana Seismic Network (UMSN), the Montana Regional Seismic Network (MRSN), the Advanced National Seismic System (ANSS), temporary deployments by the United States Geological Survey (USGS), and the USArray Transportable …

Microseismic Evidence For Bookshelf Faulting In Western Montana, Ellen Mcgough Smith

Graduate Student Theses, Dissertations, & Professional Papers

One of the most seismically active regions in the western United States, far from any major plate boundary, is the Intermountain Seismic Belt (ISB). On 6 July 2017, a M5.8 earthquake occurred 11 km southeast of Lincoln, Montana within the ISB. This was the largest earthquake to occur in the state of Montana since the 1959 M7.3 Hebgen Lake earthquake. Data from the University of Montana Seismic Network (UMSN), the Montana Regional Seismic Network (MRSN), and the United States Geological Survey (USGS) were used to investigate the aftershock sequences following the M5.8 Lincoln event. We have manually picked P- and …

Probing Earth Deformation In Response To Localized Hydrologic Mass Loading, Susitna River Basin, Alaska, Andrew Parker Keene

Graduate Student Theses, Dissertations, & Professional Papers

Surface mass loading contributes a ubiquitous signal to GPS time series that can be modeled and removed for individual sources. We utilize nine GPS stations in the Susitna River watershed, Alaska, to investigate surface displacements from surface mass loading. We find that modeling atmospheric surface pressure and regional hydrologic mass reduces root mean square (RMS) error by 27-39% for all GPS time series. We observe moderate correlation between residual time series pairs and distance, with elevation differences influencing the strength of this correlation. Seasonal horizontal and vertical displacements are observed after removal of all loading models; stations displace downward and …

Kinematic Constraints On Tectonics Of The Northern Basin And Range, Dylan Schmeelk

Graduate Student Theses, Dissertations, & Professional Papers

We derive surface velocities relative to North America, using data from 1989 through 2014 in the interior northwest, to investigate kinematics from the Snake River Plain (SRP) to the Canadian border. The Centennial Tectonic Belt (CTB) exhibits similarities to the main Basin and Range Province (BRP) that suggest the CTB is an extension of the BRP, including range and fault orientation, increasing velocity magnitudes westward, and a distinct high rate of strain across the Madison Range. Calculations of fault spreading rates and orientations from geodetic data show that several faults are more active than previously assumed when compared to seismic …

Spatial Scaling Of Crustal And Lithospheric Deformation In The Western United States, Cody W. Bomberger

Graduate Student Theses, Dissertations, & Professional Papers

Deformation of continental lithosphere can extend great distances laterally from tectonic plate boundaries. This extent has been used to argue for a variety of constitutive laws for continental materials, based on the underlying principles in continuum mechanics that identify a relationship between characteristic spatial scale and material properties. Although the relationship between observed deformation and material models is always non-unique, quantifying one or more characteristic scales of deformation in a region can rule out some models of how the lithosphere deforms. In the western United States active deformation occurs at the plate boundary between North America and either the Pacific …