Date of Award
Doctor of Philosophy
Aaron A. Velasco
Chapter 1: Investigating Earthquake Cycle Vertical Deformation Recorded by GPS And Regional Tide Gauge Stations in California
Geodetic and tide gauge measurements of vertical deformation record localized zones of uplift and subsidence that may document critical components of both long and short-period earthquake cycle deformation. In this study, we compare vertical tide gauge data from the Permanent Service for Mean Sea Level (PSMSL) and vertical GPS data from the EarthScope Plate Boundary Observatory (PBO) for 10 approximately co-located station pairs along coastal California from Point Reyes, CA to Ensenada, Mexico. To compare these two data sets, we first truncate both data sets so that they span a common time frame for all stations (2007 - 2019). PSMSL data are treated for both average global sea level rise (~1.8 mm/yr) and global isostatic adjustment. We then calculate a 2-month running mean for tide gauge and a 1-month running mean for GPS data sets to smooth out daily oceanographic or anthropologic disturbances but maintain the overall trend of each data set. As major ocean-climate signals, such as El Nino, are considered regional features of the Pacific Ocean and likely common to all California tide gauge stations, we subtract a reference sea level record (San Francisco station) from all other stations to eliminate this signal. The GPS and tide gauge data show varying degrees of correlation spanning both 3-month and 4-year time-scales. We then model vertical displacements and infer that the slope of vertical displacements is largely controlled by interseismic motions; however, displacements from major earthquakes are evident and are required to explain some of the unique signatures in the tide gauge and GPS data. Specifically, we find that stations from both data sets in Southern California show an anomalous trend since the 2010 Baja California earthquake. Long-term tide gauge time series are well simulated by the models, but short-term time series are not as well predicted; additional parameter adjustments are needed to improve these. Alternatively, both tide gauge and GPS data show a better short-term than long-term correlation; oceanographic and possibly groundwater effects could be responsible for these differences.
Chapter 2: Dynamic Stress Modeling for Investigating Tremor Source Regions in The San Andreas Fault
The frictional and stress conditions at aseismic depths in tectonic boundaries are difficult to estimate, yet these are important parameters in computing stress transfer from plate motion to the seismogenetic zones of the plate boundaries, and thus, in creating seismic hazard models. Seismic waves can trigger tremor in different tectonic environments. Triggered tectonic tremor can be useful in the estimation of friction and stress parameters at large crustal depths. Triggered tremor along the San Andreas Fault system in California is well located and documented, a large number of ambient and triggered tremors have been reported near the creeping to locking transition zone along the Parkfield-Cholame section as well as in the San Jacinto and Calaveras Faults. In this work, we show the use of dynamic triggering stress modeling as a tool for estimating the frictional conditions at the source regions where tremor occur along the San Andreas Fault.
Chapter 3: Evaluation of the Pathways to Geoscience Summer Camp Over a 3-year Period
Recruiting, retaining, and preparing the next generation of diverse geoscientists requires exposing students to the wide range of career opportunities and emerging geoscience topics and environmental issues through hands-on activities and research experiences. Various effective and evidence-based strategies must be employed to engage a diverse student population for the nation to remain a leader in the geosciences. This study describes one such strategy reaching high school students, the Pathways Geosciences High Summer Camp, funded by Shell Oil Company and hosted by the University of Texas at El Paso (UTEP). The camp ran for two weeks for the past three summers (2017, 2018, and 2019), and was based on the Pathways to the Geosciences camp, funded by the National Science Foundation and Shell, that ran from 2002-2012. Themed around interdisciplinary Earth science topics, minority high school students from local schools are immersed in workshops, field trips, and hands-on activities highlighting the city's landmarks and some of the most sought-after careers in geoscience. We measure program effectiveness using pre- and post- surveys and analyze the results using parametric and non-parametric statistical analyses. Overall, results from past summer camps demonstrate that the Pathways Geoscience Summer Camp is an effective outreach tool to recruit minority students into STEM based programs.
Received from ProQuest
Hardy, Sandra, "Geophysical Investigations Of The San Andreas Fault System And Evaluations In Geoscience Education" (2020). Open Access Theses & Dissertations. 2980.