Matching Items (6)
Description
The San Andreas Fault (SAF) is the primary structure within a system of faults accommodating motion between the North American and Pacific plates. Physical models of faulting and characterizations of seismic hazard are informed by investigations of paleoseismology, slip distribution, and slip rate. The impact of earthquakes on people is due in large part to social vulnerability. This dissertation contributes an analysis about the relationships between earthquake hazard and social vulnerability in Los Angeles, CA and investigations of paleoseismology and fault scarp array complexity on the central SAF. Analysis of fault scarp array geometry and morphology using 0.5 m digital elevation models along 122 km of the central SAF reveals significant variation in the complexity of SAF structure. Scarp trace complexity is measured by scarp separation, changes in strike, fault trace gaps, and scarp length per SAF kilometer. Geometrical complexity in fault scarp arrays indicates that the central SAF can be grouped into seven segments. Segment boundaries are controlled by interactions with subsidiary faults. Investigation of an offset channel at Parkfield, CA yields a late Holocene slip rate of 26.2 +6.4/- 4.3 mm/yr. This rate is lower than geologic measurements on the Carrizo section of the SAF and rates implied by far-field geodesy. However, it is consistent with historical observations of slip at Parkfield. Paleoseismology at Parkfield indicates that large earthquakes are absent from the stratigraphic record for at least a millennia. Together these observations imply that the amount of plate boundary slip accommodated by the main SAF varies along strike. Contrary to most environmental justice analyses showing that vulnerable populations are spatially-tied to environmental hazards, geospatial analyses relating social vulnerability and earthquake hazard in southern California show that these groups are not disproportionately exposed to the areas of greatest hazard. Instead, park and green space is linked to earthquake hazard through fault zone regulation. In Los Angeles, a parks poor city, the distribution of social vulnerability is strongly tied to a lack of park space. Thus, people with access to financial and political resources strive to live in neighborhoods with parks, even in the face of forewarned risk.
ContributorsToké, Nathan A (Author) / Arrowsmith, J R (Thesis advisor) / Boone, Christopher G (Committee member) / Heimsath, Arjun M (Committee member) / Shock, Everett L (Committee member) / Whipple, Kelin X (Committee member) / Arizona State University (Publisher)
Created2011
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
A series of experiments were conducted to support validation of a numerical model for the performance of geomembrane liners subject to waste settlement and seismic loading. These experiments included large scale centrifuge model testing of a geomembrane-lined landfill, small scale laboratory testing to get the relevant properties of the materials used in the large scale centrifuge model, and tensile tests on seamed geomembrane coupons. The landfill model in the large scale centrifuge test was built with a cemented sand base, a thin film NafionTM geomembrane liner, and a mixture of sand and peat for model waste. The centrifuge model was spun up to 60 g, allowed to settle, and then subjected to seismic loading at three different peak ground accelerations (PGA). Strain on the liner and settlement of the waste during model spin-up and subsequent seismic loading and accelerations throughout the model due to seismic loading were acquired from sensors within the model. Laboratory testing conducted to evaluate the properties of the materials used in the model included triaxial compression tests on the cemented sand base, wide-width tensile testing of the thin film geomembrane, interface shear testing between the thin film geomembrane and the waste material, and one dimensional compression and cyclic direct simple shear testing of the sand-peat mixture used to simulate the waste. The tensile tests on seamed high-density polyethylene (HDPE) coupons were conducted to evaluate strain concentration associated with seams oriented perpendicular to an applied tensile load. Digital image correlation (DIC) was employed to evaluate the strain field, and hence seam strain concentrations, in these tensile tests. One-dimensional compression tests were also conducted on composite sand and HDPE samples to evaluate the compressive modulus of HDPE. The large scale centrifuge model and small scale laboratory tests provide the necessary data for numerical model validation. The tensile tests on seamed HDPE specimens show that maximum tensile strain due to strain concentrations at a seam is greater than previously suggested, a finding with profound implications for landfill liner design and construction quality control/quality assurance (QC/QA) practices. The results of the one-dimensional compression tests on composite sand-HDPE specimens were inconclusive.
ContributorsGutierrez, Angel (Author) / Kavazanjian, Edward (Thesis advisor) / Zapata, Claudia (Committee member) / Jang, Jaewon (Committee member) / Arizona State University (Publisher)
Created2016
Description
There is a need to understand spatio-temporal variation of slip in active fault zones, both for the advancement of physics-based earthquake simulation and for improved probabilistic seismic hazard assessments. One challenge in the study of seismic hazards is producing a viable earthquake rupture forecast—a model that specifies the expected frequency and magnitude of events for a fault system. Time-independent earthquake forecasts can produce a mismatch among observed earthquake recurrence intervals, slip-per-event estimates, and implied slip rates. In this thesis, I developed an approach to refine several key geologic inputs to rupture forecasts by focusing on the San Andreas Fault in the Carrizo Plain, California. I use topographic forms, sub-surface excavations, and high-precision geochronology to understand the generation and preservation of slip markers at several spatial and temporal scales—from offset in a single earthquake to offset accumulated over thousands of years. This work results in a comparison of slip rate estimates in the Carrizo Plain for the last ~15 kyr that reduces ambiguity and enriches rupture forecast parameters. I analyzed a catalog of slip measurements and surveyed earth scientists with varying amounts of experience to validate high-resolution topography as a supplement to field-based active fault studies. The investigation revealed that (for both field and remote studies) epistemic uncertainties associated with measuring offset landforms can present greater limitations than the aleatoric limitations of the measurement process itself. I pursued the age and origin of small-scale fault-offset fluvial features at Van Matre Ranch, where topographic depressions were previously interpreted as single-event tectonic offsets. I provide new estimates of slip in the most recent earthquake, refine the centennial-scale fault slip rate, and formulate a new understanding of the formation of small-scale fault-offset fluvial channels from small catchments (<7,000 m2). At Phelan Creeks, I confirm the constancy of strain release for the ~15,000 years in the Carrizo Plain by reconstructing a multistage offset landform evolutionary history. I update and explicate a simplified model to interpret the geomorphic response of stream channels to strike-slip faulting. Lastly, I re-excavate and re-interpret paleoseismic catalogs along an intra-continental strike-slip fault (Altyn Tagh, China) to assess consistency of earthquake recurrence.
ContributorsSalisbury, J. Barrett (Author) / Arrowsmith, Ramon (Thesis advisor) / Shirzaei, Manoochehr (Committee member) / DeVecchio, Duane (Committee member) / Whipple, Kelin (Committee member) / Heimsath, Arjun (Committee member) / Arizona State University (Publisher)
Created2016
Description
Ground-motion data from the February 6th, 2023 Kahmaranmaraş, Türkiye earthquake sequence is analyzed. Acceleration and deformation response spectra are analyzed to predict susceptible infrastructure and failure mechanisms of reinforced concrete structures in the region. Images are used to compare the theoretical failure and actual building failures in the region. Recommendations are provided for both the seismic design code and seismic retrofitting.
ContributorsMendez Aceves, Carlos (Author) / Ward, Kristen (Thesis director) / Hjelmstad, Keith (Committee member) / Barrett, The Honors College (Contributor) / Civil, Environmental and Sustainable Eng Program (Contributor)
Created2024-05
Description
This report analyzed the dynamic response of a long, linear elastic concrete bridge subject to spatially varying ground displacements as well as consistent ground displacements. Specifically, the study investigated the bridge’s response to consistent ground displacements at all supports (U-NW), ground displacements with wave passage effects and no soil profile variability (U-WP), and ground displacements with both wave passage effects and soil profile variability (V-WP). Time-history ground displacements were taken from recordings of the Loma Prieta, Duzce, and Chuetsu earthquakes. The two horizontal components of each earthquake time-history displacement record were applied to the bridge supports in the transverse and longitudinal directions. It was found that considering wave passage effects without soil profile variability, as compared with consistent ground displacements, significantly reduced the peak total energy of the system, as well as decreasing the maximum relative longitudinal displacements. The maximum relative transverse displacements were not significantly changed in the same case. It was also found that including both wave passage effects and soil profile variability (V-WP) generally resulted in larger maximum transverse relative displacements, across all earthquake time-histories tested. Similarly, it was found that using consistent ground displacements (U-NW) generally resulted in larger maximum longitudinal relative displacements, as well as larger peak total energy values.
ContributorsSeawright, Jordan Michael (Author) / Hjelmstad, Keith (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2019