Evaluating the Sensitivity of Crustal Deformation to Bedrock Hydrology in a Mountain Watershed

Author

Brett J. Oliver, University of Montana, MissoulaFollow

Year of Award

2023

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Geosciences

Department or School/College

Geosciences

Committee Chair

W. Payton Gardner

Commitee Members

Hilary R. Martens Zachary Hoylman

Keywords

Groundwater, Geophysics, Hydrogeology, Hydrology, Geodesy, Numerical Modeling

Publisher

University of Montana

Subject Categories

Geophysics and Seismology | Hydrology

Abstract

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 storage calculated by each groundwater simulation. We perform theoretical sensitivity analyses to groundwater system parameterization by simulating changes in deformation as a result of different subsurface properties for synthetic seasonal recharge. Initial results indicate that crustal displacements are sensitive to perturbations in bedrock hydraulic conductivity, storativity, and thickness. Changes in these parameters affect the minimum and maximum amplitude of peak crustal displacement as well as the timing of when these peaks occur. This method could improve the bulk parameterization of bedrock within mountainous regions with adequate GPS network density and precision at sufficiently large scales. Our modeling framework offers a new tool to parameterize deep bedrock for numerical groundwater simulations using geodetic observations, which is challenging in mountainous watersheds where extremely limited groundwater data is available.

Recommended Citation

Oliver, Brett J., "Evaluating the Sensitivity of Crustal Deformation to Bedrock Hydrology in a Mountain Watershed" (2023). Graduate Student Theses, Dissertations, & Professional Papers. 12233.
https://scholarworks.umt.edu/etd/12233