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- Member of: ASU Electronic Theses and Dissertations
- Status: Published
Description
This study focuses on mapping faults along the Creeping Section of the San Andreas Fault (CSAF) in California between San Juan Bautista (121.54°W 36.85°N) and Parkfield (120.41°W 35.87°N). I synthesize high-quality base data, including and lidar topography from B4, EarthScope, and USGS 3DEP, recent maps of decadal-scale along-fault shear strain, and aerial and satellite imagery. Using these data, I produced (covering 150 km at 1:10,000 scale) three geospatial map datasets with attributes: geomorphic indicators of faulting, surficial geology, and active fault traces.The CSAF's creeping movement, though likely not associated with large earthquakes, has the potential to cause damage to infrastructure. Accurate fault mapping facilitates fault displacement hazard assessment. This type of work is useful for California state regulations, particularly the Alquist-Priolo Act of 1972, providing insights for engineering site assessments and fault exclusion zones.
I discern, categorize, and rank geomorphic indicators to support fault line placement. This approach contributes to the identification of surface expression of creeping faults where the surface has undergone alteration in response to displacement along the fault. I created a surficial geologic map spanning from San Juan Bautista to the southern extent of EarthScope lidar coverage (120.59°W 36.03°N). I categorized each fault as either a primary or secondary fault trace and further broke them into confidence levels based on interpretations of indicators along with structural geologic reasoning and
topographic patterns. Accessible target areas containing initial low confidence mapping or interesting structures were visited in the field.
Zones along the creeping section exhibit structures such as a pressure ridge found 25 km north of Parkfield, sigmoidal faults and sagponds observed near Paicines Ranch (121.29°W 36.68°N), en-echelon faults, horsetail splays and Riedel shear structures near Lewis Creek (120.87°W 36.29°N). Controls on the structural style along the CSAF are the results of geologic units through which the faults cut and fault zone width and trend.
ContributorsPowell, Joseph Hoss (Author) / Arrowsmith, Ramon (Thesis advisor) / Scott, Chelsea (Thesis advisor) / DeVecchio, Duane (Committee member) / DeLong, Stephen (Committee member) / Arizona State University (Publisher)
Created2023