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.

Accurate fault maps are an important component in the assessment of hazard from fault displacement. Different mapping techniques, biases and ambiguous geomorphic evidence for faulting can drive even expert mappers to produce different fault maps. Another challenge is that future ruptures may not follow past ruptures, so available evidence in the landscape may not lead to accurate rupture prediction. The ultimate goal of my work is to develop a systematized approach for fault mapping so that resulting maps are more evidence-based and ultimately of higher quality I systematized the active fault mapping process and the documentation of evidence for potential fault rupture. I developed and taught a systematic mapping process based on geomorphic landforms evident in remote sensing datasets to undergraduate students, graduate students, and geologic professionals. My approach uses data acquired before historic ruptures to make and test “pre-rupture” fault traces based on the landscape morphology, geomorphology, and geology. The mappers used the Geomorphic Indicator Ranking system (GIR) to represent the geomorphic evidence for faulting such as scarps, triangular facets, offset features, beheaded drainages, and many more. I evaluated the approach in three ways: (1) To assess the geomorphology that best predicts future rupture, I compared the separation distance between the mapped geomorphologic features and the rupture. Scarps and lineaments performed best. (2) I compared the fault confidence chosen by the mapper versus that computed from GIR elements (i.e., mapped geomorphology) near the fault traces. Accurately characterizing fault confidence requires a balance between the mapper input and the calculated confidence rankings. (3) I conducted listening sessions with 21 participants to understand each participant’s approach to fault mapping to highlight best practices and challenges of geomorphic fault mapping. The terminology and mapping process vary by experience level. My approach works both as a teaching tool to introduce tectonic geomorphology and fault mapping to novice mappers, but also works in an industry setting to establish consistent documentation for fault maps. These higher quality fault maps have implications applications of fault mapping including easier dissemination of information, comparison between different fault maps, and hopefully more accurate fault locations for hazard mitigation.

This study presents an analysis of fault scarps, with a focus on implementing the Landlab computational toolkit to model fault scarp evolution and analyzing fault scarps under transport and production-limited conditions with linear and nonlinear diffusive transport laws. The aim of the study is to expand diffusion modeling of fault scarps from 1D to 2D by using Landlab toolkit. The study evaluated two fault scarps in western US (NE California): one representing an old fault scarp (Twin Butte) and the other representing a young fault scarp (Active Hat Creek Fault). High-resolution digital elevation models (DEMs) were used to generate 2D surfaces of the fault scarps, which were then converted to 1D profiles for morphological modeling and analysis. The accuracy of the models was evaluated using Root Mean Squared Error (RMSE), and the best-fit models were selected for further examination. The grid search of the non-linear diffusion model of the Twin Butte and Active Hat Creek fault scarps showed optimum values for transport constant (k) and scarp age (t) that aligned with the apparent ages of the rocks and associated fault scarps. For both fault scarps, the optimum k value was around 7.5 m2 /kyr, while the optimum t value was around 110 kyr for the Twin Butte scarp and around 26 kyr for the Active Hat Creek scarp. The results suggest that the geomorphic processes (influenced by climate and rock types) in both fault scarps are similar, despite the difference in age and location. Integrating tectonic displacement in the model helps to better capture the observed patterns of tectonic deformation. The expansion of the fault scarps diffusion model from 1D to 2D opens up a range of fascinating possibilities, as it enables us to model the lateral movement of particles that the 1D model typically overlooks. By incorporating this additional dimension, we can better understand the complex interplay between vertical and horizontal displacements, providing a more accurate representation of the geological processes at work. This advancement ultimately allows for a more comprehensive analysis of fault scarps and their development over time, enhancing our understanding of Earth's dynamic crustal movements.