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- Genre: Masters Thesis
Description
Meter-resolution topography gathered by LiDAR (Light Detection and Ranging) has become an indispensable tool for better understanding of many surface processes including those sculpting landscapes that record information about earthquake hazards for example. For this reason, and because of the spectacular representation of the phenomena that these data provide, it is appropriate to integrate these data into Earth science educational materials. I seek to answer the following research question: "will using the LiDAR topography data instead of, or alongside, traditional visualizations and teaching methods enhance a student's ability to understand geologic concepts such as plate tectonics, the earthquake cycle, strike-slip faults, and geomorphology?" In order to answer this question, a ten-minute introductory video on LiDAR and its uses for the study of earthquakes entitled "LiDAR: Illuminating Earthquake Hazards" was produced. Additionally, LiDAR topography was integrated into the development of an undergraduate-level educational activity, the San Andreas fault (SAF) earthquake cycle activity, designed to teach introductory Earth science students about the earthquake cycle. Both the LiDAR video and the SAF activity were tested in undergraduate classrooms in order to determine their effectiveness. A pretest and posttest were administered to introductory geology lab students. The results of these tests show a notable increase in understanding LiDAR topography and its uses for studying earthquakes from pretest to posttest after watching the video on LiDAR, and a notable increase in understanding the earthquake cycle from pretest to posttest using the San Andreas Fault earthquake cycle exercise. These results suggest that the use of LiDAR topography within these educational tools is beneficial for students when learning about the earthquake cycle and earthquake hazards.
ContributorsRobinson, Sarah Elizabeth (Author) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen J. (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2011
Description
The goal of this study is to gain a better understanding of earthquake distribution and regional tectonic structure across Arizona. To achieve this objective, I utilized seismic data from EarthScope's USArray Transportable Array (TA), which was deployed in Arizona from April 2006 to March 2009. With station spacing of approximately 70 km and ~3 years of continuous three-component broadband seismic data, the TA provided an unprecedented opportunity to develop the first seismicity catalog for Arizona without spatial sampling bias. In this study I developed a new data analysis workflow to detect smaller scale seismicity across a regional study area, which serves as a template for future regional analyses of TA data and similar datasets. The final event catalog produced for this study increased the total number of earthquakes documented in Arizona by more than 50% compared to the historical catalog, despite being generated from less than three years of continuous waveform data. I combined this new TA catalog with existing earthquake catalogs to construct a comprehensive historical earthquake catalog for Arizona. These results enabled the identification of several previously unidentified areas of seismic activity within the state, as well as two regions characterized by seismicity in the deeper (>20 km) crust. The catalog also includes 16 event clusters, 10 of which exhibited clear temporal clustering and swarm-like behavior. These swarms were distributed throughout all three physiographic provinces, suggesting that earthquake swarms occur regardless of tectonic or physiographic setting. I also conducted a case study for an earthquake swarm in June of 2007 near Theodore Roosevelt Lake, approximately 80 miles northeast of Phoenix. Families of events showed very similar character, suggesting a nearly identical source location and focal mechanism. We obtained focal mechanisms for the largest of these events, and found that they are consistent with normal faulting, expected in this area of the Arizona Transition Zone. Further, I observed no notable correlation between reservoir water level and seismicity. The occurrence of multiple historical earthquakes in the areas surrounding the reservoir indicates that this swarm was likely the result of tectonic strain release, and not reservoir induced seismicity.
ContributorsLockridge, Jeffrey Steven (Author) / Fouch, Matthew J (Thesis advisor) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen J. (Committee member) / Arizona State University (Publisher)
Created2011
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
Description
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.
ContributorsAdam, Rachel (Author) / Scott, Chelsea (Thesis advisor) / Arrowsmith, Ramon (Thesis advisor) / Reano, Darryl (Committee member) / Arizona State University (Publisher)
Created2023
Description
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.
ContributorsHafiz, Abdel (Author) / Arrowsmith, Ramon (Thesis advisor) / Whipple, Kelin (Committee member) / Scott, Chelsea (Committee member) / Arizona State University (Publisher)
Created2023
Description
The study of fault zones is a critical component to understanding earthquake mechanics and seismic hazard evaluations. Models or simulations of potential earthquakes, based on fault zone properties, are a first step in mitigating the hazard. Theoretical models of earthquake ruptures along a bi-material interface result in asymmetrical damage and preferred rupture propagation direction. Results include greater damage intensity within stiffer material and preferred slip in the direction of the more compliant side of the fault. Data from a dense seismic array along the Clark strand of the SJFZ at Sage Brush Flat (SGB) near Anza, CA, allows for analysis and characterization of shallow (<1km depth) seismic structure and fault zone properties. Results indicate potential asymmetric rock damage at SGB, similar to findings elsewhere along the SJFZ suggesting an NW preferred rupture propagation.
In this study, analysis of high resolution topography suggests asymmetric morphology of the SGB basin slopes are partially attributed to structural growth and fault zone damage. Spatial distributions of rock damage, from site mapping and fault perpendicular transects within SGB and Alkali Wash, are seemingly asymmetric with pulverization dominantly between fault strands or in the NE fault block. Remapping of the SJFZ through Alkali Wash indicates the fault is not isolated to a single strand along the main geologic boundary as previously mapped. Displacement measurements within SGB are analogous to those from the most recent large earthquake on the Clark fault. Geologic models from both a 3D shear wave velocity model (a product from the dense seismic array analysis) and lithologic and structural mapping from this study indicate surface observations and shallow seismic data compare well. A synthetic three-dimensional fault zone model illustrates the complexity of the structure at SGB for comparison with dense array seismic wave products. Results of this study generally agree with findings from seismic wave interpretations suggesting damage asymmetry is controlled by a NW preferred rupture propagation.
In this study, analysis of high resolution topography suggests asymmetric morphology of the SGB basin slopes are partially attributed to structural growth and fault zone damage. Spatial distributions of rock damage, from site mapping and fault perpendicular transects within SGB and Alkali Wash, are seemingly asymmetric with pulverization dominantly between fault strands or in the NE fault block. Remapping of the SJFZ through Alkali Wash indicates the fault is not isolated to a single strand along the main geologic boundary as previously mapped. Displacement measurements within SGB are analogous to those from the most recent large earthquake on the Clark fault. Geologic models from both a 3D shear wave velocity model (a product from the dense seismic array analysis) and lithologic and structural mapping from this study indicate surface observations and shallow seismic data compare well. A synthetic three-dimensional fault zone model illustrates the complexity of the structure at SGB for comparison with dense array seismic wave products. Results of this study generally agree with findings from seismic wave interpretations suggesting damage asymmetry is controlled by a NW preferred rupture propagation.
ContributorsWade, Adam Micahel (Author) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen (Committee member) / DeVecchio, Duane (Committee member) / Arizona State University (Publisher)
Created2018
Description
Understanding topography developed above an active blind thrust fault is critical to quantifying the along-strike variability of the timing, magnitude, and rate of fault slip at depth. Hillslope and fluvial processes respond to growing topography such that the existing landscape is an indicator of constructional and destruction processes. Light detection and ranging (lidar) data provide a necessary tool for fine-scale quantitative understanding of the topography to understand the tectonic evolution of blind thrust faulting. In this thesis, lidar topographic data collected in 2014 are applied to a well-studied laterally propagating anticline developed above a blind thrust fault in order to assess the geomorphic response of along-strike variations in tectonic deformation. Wheeler Ridge is an asymmetric east-propagating anticline (10 km axis, 330 m topographic relief) above a north-vergent blind thrust fault at the northern front of the Transverse Ranges, Southern San Joaquin Valley, California. Wheeler Ridge is part of a thrust system initiating in the late Miocene and is known to have significant historic earthquakes occur (e.g., 1952 Mw 7.3 Kern County earthquake). Analysis of the lidar data enables quantitative assessment of four key geomorphic relationships that may be indicative of relative variation in local rock uplift. First, I observe remnant landforms in the youngest, easternmost section of Wheeler Ridge that indicate the erosional history of older deposits to the west. Second, I examine the central portion of Wheeler Ridge where drainages and hillslopes are closely tied to uplift rates. Third, I observe the major wind gap within which a series of knickpoints are aligned at a similar elevation and tie into the local depositional and uplift history. Finally, I survey the western section and specifically, the fold backlimb where high-resolution topography and field mapping indicate long ridgelines that may preserve the uplifted and tilted alluvial fan morphology. I address changing landforms along the fold axis to test whether backlimb interfluves are paleosurfaces or the result of post-tectonic erosional hillslope processes. This work will be paired with future geochronology to update the ages of uplifted alluvial fan deposits and better constrain the timing of along-strike uplift of Wheeler Ridge.
ContributorsKleber, Emily (Author) / Arrowsmith, Ramon (Thesis advisor) / DeVecchio, Duane E (Committee member) / Whipple, Kelin X (Committee member) / Arizona State University (Publisher)
Created2015
Description
Rock traits (grain size, shape, orientation) are fundamental indicators of geologic processes including geomorphology and active tectonics. Fault zone evolution, fault slip rates, and earthquake timing are informed by examinations of discontinuities in the displacements of the Earth surface at fault scarps. Fault scarps indicate the structure of fault zones fans, relay ramps, and double faults, as well as the surface process response to the deformation and can thus indicate the activity of the fault zone and its potential hazard. “Rocky” fault scarps are unusual because they share characteristics of bedrock and alluvial fault scarps. The Volcanic Tablelands in Bishop, CA offer a natural laboratory with an array of rocky fault scarps. Machine learning mask-Region Convolutional Neural Network segments an orthophoto to identify individual particles along a specific rocky fault scarp. The resulting rock traits for thousands of particles along the scarp are used to develop conceptual models for rocky scarp geomorphology and evolution. In addition to rocky scarp classification, these tools may be useful in many sedimentary and volcanological applications for particle mapping and characterization.
ContributorsScott, Tyler (Author) / Arrowsmith, Ramon (Thesis advisor) / Das, Jnaneshwar (Committee member) / DeVecchio, Duane (Committee member) / Arizona State University (Publisher)
Created2020