Browsing by Subject "Fault"
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Item Analysis of the effects of carbonate mounds on associated stratal geometry and fracture development, Sacramento Mountains, New Mexico, USA(2016-12) Tinker, Nathan Scott; Janson, Xavier; Zahm, Christopher Kent; Kerans, Charles; Fisher, William LThe objective of this research is an integrated structural‐stratigraphic analysis of compaction‐related fracturing in carbonate mounds and associated cover strata. The influence of early-cemented carbonate mounds on subsequent sediment deposition (such as creation of hard substrates and topographic relief) is relatively well-understood. The effect of early-cemented carbonate mounds during burial, however, has not been studied in detail. Early marine cementation of mounds enhances mechanical rigidity, which reduces mound compaction during burial as compared to less-resistant sediments surrounding and overlying the mound. This rigidity difference facilitates differential compaction of sediments overlying the mound, which are warped over the inflection point created by the mound topography. This study hypothesizes that there is a measurable increase in fracture intensity associated with differential compaction above early-lithified carbonate mounds. Thus, this work analyzes and quantifies the effects of differential compaction on stratal geometry, mechanical stratigraphy, and fracture development in Mississippian strata overlying carbonate mounds which are well-exposed in the Sacramento Mountains in southeast New Mexico. Methods employed in this study are drawn from structural geology, sedimentology, petrography, and remote sensing in an effort to adequately determine facies, examine fracture characteristics (e.g. size, orientation, and intensity), and to better understand which process(es) most directly control those characteristics (e.g. host rock facies type, diagenesis, bed thickness, mound proximity, mound size). Innovative methods of outcrop characterization such as high-resolution gigapan photography and unmanned aerial vehicle (UAV) photography were combined with photogrammetric techniques to create photo-realistic 3D outcrop models. The resulting models enabled a cost-effective, more detailed, less-distorted, and more comprehensive interpretation compared to previous methods, and improved understanding of the relationship between stratigraphy, rock mechanical evolution, and structural deformation in carbonate mound systems. Field work documented facies, stratal geometries, folds, faults, and fracture sets which validated observations and characterizations made using high-resolution field photographs and 3D outcrop models. Results of this work show that paleotopographic relief which has been early lithified (in this instance, Mississippian carbonate mounds) directly controls fracture development and overlying stratal geometry, in that there is a significant increase in tension fracture (mode 1) intensity above pre-existing rigid structures and over-steepening of bed dips beyond an expected and reasonable angle of repose. Additionally, this work outlines a multi-stage tectonostratigraphic sequence of the development of the stratigraphically complex Teepee Mound assemblage based on field observations of facies, fractures, stratal geometries, and diagenetic effects (e.g. cementation, compaction, and chertification), which includes new evidence of late-Mississippian tectonic compression. This result emphasizes the importance of understanding both syndepositional and post-depositional processes in outcrop characterization. Specifically, syndepositional processes establish the original mechanical stratigraphy and control the formation and propagation of early mechanical discontinuities, which in turn set up the fabric of weaknesses preferentially utilized by later fracture development. Post-depositional mechanical and diagenetic processes alter mechanical stratigraphy and rock brittleness, and thus influence fracture propagation through time.Item Fold-related brittle structures and associated strain in a limestone bed of the Carmel Formation, San Rafael Swell, Utah(2015-12) Laciano, Peter Joseph; Marrett, Randall; Cloos, Mark; Ukar, EstibalitzThe San Rafael Swell (SRS) is a basement-cored Laramide uplift located in central-eastern Utah. The SRS is bounded on the east by a 70 km long monocline, a fault-propagation fold, with excellent exposure of sedimentary strata including the Carmel Formation. This monocline is an ideal natural laboratory for studying brittle deformation associated with folding. Qualitative and quantitative observations for brittle structures in a limestone bed near the base of the Carmel Fm. were made in a wide range of bedding dip, curvature, and fold domains. Kinematic data was collected for 2942 structures (1865 veins, 746 stylolites, 314 faults) in 30 locations in order to calculate principal directions of strain. Additionally, data was collected along 71 scanlines at 19 of those locations in order to estimate structure intensities and strain magnitudes. Dekameter-displacement thrust faults, acting as ramps between inferred layer-parallel faults, accommodate orders of magnitude more strain than all other observed brittle structures. These faults are only found in segments of the monocline where bedding dip is high, but curvature is low, which provides strong evidence that limb rotation more strongly controls strain magnitudes than layer bending in the SRS. The trishear model effectively predicts SRS monocline geometry, specifically observed limb thickening, broad, curved hinges, and progressively rotating limb. This is likely due to the dominance of thick, homogeneous rock packages, such as the Navajo Sandstone, in the SRS monocline. In contrast, strain localization within the Carmel Fm. is poorly predicted by trishear: there is strong evidence of flexural slip, and folding induced structure orientations and calculated principal strain directions remain consistent relative to bedding. These strain directions are inconsistent with trishear forward models produced by workers such as Zuluaga et al. (2014) that do not stay consistent relative to bedding. These divergences are likely due to the fact that trishear is a kinematic model that assumes rock homogeneity, while the Carmel Fm. is stratigraphically and mechanically heterogeneous. Because this heterogeneity appears to have a strong effect on strain localization, kink band models likely better estimate strain localization in the Carmel limestone bed as well as other layers in folded heterogeneous strata. The monocline’s interpreted transition from layer-parallel shortening to extension at the steepest locations in the monocline, and thus at most advanced stage of folding, enabled estimation of the dip of the basement fault beneath the SRS as ~30°. This shallow dip contrasts with the steep dip (~60°) assumed for the SRS by Zuluaga et al. (2014) and observed in the Kaibab uplift (Huntoon and Sears, 1975; Tindall, 2000), but is consistent with a recent estimation of 20-40° for the SRS by Davis and Bump (2009) using trishear modeling.Item Limitations for detecting small-scale faults using the coherency analysis of seismic data(Texas A&M University, 2006-08-16) Barnett, David BenjaminCoherency analyzes the trace to trace amplitude similarities recorded by seismic waves. Coherency algorithms have been used to identify the structural or stratigraphic features of an area but the limitations for detecting small-scale features are not known. These limitations become extremely important when interpreting coherency within poorly acquired or processed data sets. In order to obtain a better understanding of the coherency limitations, various synthetic seismic data sets were created. The sensitivity of the coherency algorithms to variations in wave frequency, signal-to-noise ratio and fault throw was investigated. Correlation between the coherency values of a faulted reflector and the known offset shows that coherency has the ability to detect the presence of various scale features that may be previously thought to be below seismic resolution or difficult to discriminate with conventional interpretation methods. Coherency values had a smaller standard deviation and were less sensitive to noise when processed with a temporal window length less than one period. A fault could be detected by coherency when the signal-to-noise ratio was >3. A fault could also be detected as long as the throw-to-wavelength ratio was >5% or two-way traveltime-toperiod >10%. Therefore, this study suggests that coherency has the ability to detect a fault as long as the frequency of the data imaging that fault has a period no greater than one order of magnitude to the traveltime through the fault and that the signal can easily be distinguished from noise. Results from application of the coherency analysis were applied to the characterization of a very deep fault and fracture system imaged by a field seismic data set. A series of reverse and strike-slip faults were detected and mapped. Magnitudes of the throws for these faults were not known, but subtle amplitude anomalies in seismic sections confirmed the coherency analysis. The results of this study suggest that coherency has demonstrated an ability to detect features that would normally beoverlooked using traditional interpretation methods and has many future implications for poorly imaged seismic areas, such as sub-salt.Item Software fault localization with theory of evidence(2010-12) Jordan, Adam L.; Hewett, Rattikorn; Shin, Michael; Zhang, YuanlinSoftware development is a worldwide business that affects almost all aspects of our lives. In the cycle of software development, software debugging is the most time consuming phase and in debugging, the process of locating software faults takes the majority of the time. The process of automating fault localization is a valuable asset to any development of large scale software. The larger an application scales, the more complex it becomes, and the more difficult it becomes to manage and locate faults within the software. Automated software fault localization is used to try to locate a fault with little or no human intervention. In the past, this has been accomplished by analyzing test cases, execution sequences, logical predicates, memory states, and various other methods. This thesis presents a new technique of automated software fault localization that is based on theory of evidence for uncertainty reasoning to estimate likelihoods of faulty locations. The proposed technique is evaluated and compared to the three best-performing methods presently available using a set of benchmark programs in an empirical study. The study compares the methods‟ abilities to reduce the amount of code that needs to be viewed to locate a fault. The results show that the proposed technique performed no worse than these top techniques in 100% of all the program versions in the benchmark set with an average of over 85% of effectiveness measure.