Exploring Effects of GPS Processing on Atmospheric and Hydrologic Pressure-induced Crustal Responses
Graduation Year
2020
Graduation Month
May
Document Type
Thesis
Degree Name
Bachelor of Arts
School or Department
Physics and Astronomy
Major
Physics – Astronomy
Faculty Mentor Department
Geosciences
Faculty Mentor
Hilary Martens
Keywords
GPS, surface mass loading, atmospheric loading, hydrologic loading
Subject Categories
Geophysics and Seismology
Abstract
The Earth’s crust is in continuous motion from changes in fluid pressures associated with the redistribution of mass at the surface. These forces, known as surface mass loading, make up a significant amount of signal within GPS time series. This thesis is broken up into two projects exploring atmospheric and hydrologic pressure-induced crustal responses. The first project focuses on effects of GPS processing on corrections of atmospheric loading. We use data from over 1100 GPS stations within the Western US to investigate crustal displacements from atmospheric surface pressure variations. We find that modeling and removing atmospheric mass loading reduces root mean square (RMS) scatter of residual GPS time series by 16 % on average and up to 50 % for inland stations. We observe a trend of larger RMS reduction with increasing distance from the ocean, due to the inverted barometer effect. We then compare five sets of processed GPS data from three different processing centers (JPL, NGL, UNAVCO) and attempt to isolate possible causes for variations in the GPS displacements. The GPS products with the largest reductions in RMS scatter were generated using the more accurate, high resolution troposphere delays, with the UNAVCO data product providing the best retention of atmospheric mass loading (ATML) in the time series. The retention of ATML in the time series is affected by the temporal resolution of the tropospheric model used in initial processing of raw GPS signal. Mismodeling troposphere delays can lead to an inaccurate distance estimate between satellite and receiver, thereby limiting retention of atmospheric surface pressure-induced crustal displacements in the time series. As such, we recommend using high resolution tropospheric delays when possible. The second project focuses on isolating and quantifying hydrologic loading signal sources within GPS stations near the Columbia River along the Washington-Oregon border. We attempt to correlate seasonal river discharge with horizontal motions present within the GPS time series using particle motions ellipses. We also attempt correlation between sub-seasonal signals of displacement with changes in river discharge measured by USGS river gauges.
Honors College Research Project
No
GLI Capstone Project
no
Recommended Citation
Norberg, Cody T., "Exploring Effects of GPS Processing on Atmospheric and Hydrologic Pressure-induced Crustal Responses" (2020). Undergraduate Theses, Professional Papers, and Capstone Artifacts. 278.
https://scholarworks.umt.edu/utpp/278
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© Copyright 2020 Cody T. Norberg