Theses/Dissertations - Geosciences

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A hydrologic assessment of water chemistry and aquifer properties in the Middle Trinity Aquifer in Bell and McLennan Counties in Texas.
(2018-05-02) Tucker, James Joseph, 1990-; Yelderman, Joe C.
The Middle Trinity Aquifer is part of a freshwater aquifer spanning southern Oklahoma and Central Texas. Increasing demand from population growth has promoted a need to better understand productivity and associated aquifer properties, as well as variation in chemistry in areas with uncharacteristically high ionic concentrations and total dissolved solids. This study presents and analyzes data related to production capacity in Bell and McLennan Counties through two aquifer tests. This thesis uses Texas Water Development Board data to analyze the changing concentrations of ions and total dissolved solids in various formations while adding data from newly sampled wells in the study area. Variations in water quality occur in Bell County with uncharacteristically high levels of total dissolved solids and water-chemistry changes. Results from this study can be used to improve freshwater resource management in Bell and McLennan County.
Abundance and character of organic matter in cretaceous rocks of Central Texas.
(2010-02-02T19:50:39Z) Clark, Stephen M. (Stephen Matthew), 1983-; Dworkin, Stephen I.; Geology.; Baylor University. Dept. of Geology.
One of the basic tenants of organic geochemistry states that significant accumulation of organic matter will not occur in well-oxygenated aqueous environments. Changing abundance of sedimentary organic material, therefore, probably reflects changes in marine and terrestrial conditions on Earth. This study will document the abundance and character of sedimentary organic matter in Cretaceous rocks of Central Texas with the goal of reconstructing the environmental, chemical, and depositional conditions responsible for organic carbon accumulation. Organic carbon content in Central Texas ranges from .2 to over 1.5 weight percent. C/N ratios range from 5 to over 25. The C/N ratios are low in the Grayson and Pearsall formations whereas high C/N ratios are characteristic of the Walnut Clay and Lake Waco formations. Carbon isotope ratios of organic matter range from –28.8 to –22.7‰ (VPDB) with lower values occurring in the middle-Cretaceous. Lastly, most δ¹⁵N values of organic matter hover between 1 to 3‰. Although these data could suggest a terrestrial source, the influence of Cretaceous oceanic anoxic events could be causing a marine signature to appear terrestrial.
Age, genesis, and archaeological geology of the sandy mantle on the Gulf Coastal Plain of Texas.
(2013-05-15) Ahr, Steven Wayne, 1970-; Nordt, Lee C.; Geology.; Baylor University. Dept. of Geology.
Alfisols exhibiting strong textural contrasts between sandy A-E horizons (sandy mantle) and clayey Bt horizons on the Gulf Coastal Plain have invoked debate among pedologists, geologists, and archaeologists about parent material uniformity, the age and origin of the sandy mantle, and the scientific value of buried archaeological sites. This dissertation addresses these issues, as well as climate-related variability in the mass-balance of soil constituents, across a 700-mm mean annual precipitation (MAP) gradient. Five Alfisol pedons located on upland summit settings of the Gulf Coastal Plain of Texas were sampled, described, and analyzed. Depth trends in clay-free particle-size classes and Ti and Zr failed to reveal lithologic discontinuities in each pedon, suggesting that the A-E and Bt horizons are genetically related and the textural contrasts resulted from pedogenic, rather than depositional, processes. Thus, any buried archaeological materials would have moved down the profile under the influence of bioturbation and gravity. Optical dating of the soil profiles illustrates complex age structures. Mixing in the A-E horizons effects apparent OSL ages <10,000 years due to admixture of recently and partially bleached quartz grains. Decreased mixing occurs within Bt horizons, and ages increase systematically with depth. Pedogenic weathering alters 40K, U and Th content and environmental dose rates, with concomitant changes in OSL ages. Apparent maximum age calculations from the probable oldest equivalent dose group in soil parent materials suggest the soils began weathering at least by 90-112 ka, and 40-62 ka, which greatly precedes human entry into North America. Mass-balance trends revealed nearly 100% weathering losses of Ca, Mg, Na, Al, and Fe from the A-E horizons, with redistributions and variable gains in Bt horizons. Elemental flux is positively correlated with net mass flux of fine clay and MAP, likely due to increased weathering-related concentrations of negatively-charged clay particles in higher-MAP soils, which facilitate cation adorption and retention. This has implications for predicting pedogenic response to global climate change and for estimating important soil properties in Alfisol-like paleosols in the geologic record.
Analysis of calcite-filled faults in carbonate strata, balcones trend near Waco, Texas.
(2011-09-14) Secrest, Stephen H.; Cronin, Vincent S.; Geology.; Baylor University. Dept. of Geology.
Five normal faults exposed in the Lehigh Quarry near Waco, Texas, were analyzed. The mechanical stratigraphy of the quarry ranges from relatively strong chalk to marly chalk to chalky marl to relatively weak marl. Higher clay content yields weaker rock. The dip angle of the normal faults varies with rock strength, with steeper dips across the stronger strata. Carbon stable isotopes in 174 samples indicate that the water from which the calcite precipitated is formation water and not meteoric water, while oxygen isotopes indicate that precipitation of secondary calcite in the fault cores occurred between 48° and 110°C. Mechanical twins in macrospar calcite indicate shear stress slightly more than 5-15 MPa, and deformation temperature of <170°C. The microspar fabric includes thin veinlets of secondary calcite and host lithons of cemented chalk wallrock whose orientation relative to the domain boundaries can be used as a shear-sense indicator.
Application of direct current resistivity method to environmental and hydrological problems.
(2016-04-13) Xu, Tian, 1988-; Dunbar, John A., 1955-
The direct current resistivity (DCR) method is a well-established geophysical method that is widely used in environmental, civil engineering, and hydrological investigations. DCR has the advantage of producing spatial and temporal images of the subsurface in two and three dimensions at relatively high resolution compared to those produced by other electrical methods. In the past few decades, DCR method has been applied in a variety of “conventional” near surface land and marine environments. This dissertation addresses approaches to expanding the utility of DCR in conventional environments and to applying it in three different unconventional and challenging environments. Following an introduction to the research in chapter one, results of a binning method applied to continuous resistivity profiling data in water reservoirs are presented in chapter two. Results reveal that the method is computationally efficient and suitable for lacustrine environments. In chapter three, the application of the DCR method on a deep-marine, near-bottom environment is evaluated. This study shows that it is possible to collect valid DCR data in deep-marine settings to detect shallow resistivity anomalies and to map their distribution within 100 m of the seafloor. In chapter four, an application of a time-lapse azimuthal DCR method to monitor bedrock joints and soil cracking on a vertisol-shale terrain is evaluated. It is demonstrated that vertical profiles of anisotropy have the potential to quantify the density and orientation of both soil cracks and bedrock joints. Chapter five presents a brief summary and conclusions of the research.
Application of machine learning and magnetotellurics to aid in subsurface characterization of petroleum and geothermal reservoirs.
(August 2022) Rau, Elisabeth G., 1994-; Atchley, Stacy C.
Energy is the foundation of society and with future energy demand expected to increase significantly over the next few decades, solutions contributing to future energy resources are of high interest scientifically, geopolitically, and economically. Data analytics and machine learning provide useful tools to more efficiently and cost-effectively produce petroleum and geothermal resources vital for our energy future. Supervised and unsupervised machine learning can aid in the prediction of sedimentological and reservoir attributes in wells lacking core control to better and more efficiently characterize subsurface petroleum reservoirs. Using tree-based machine learning models, core-observed depositional attributes from the Late Devonian Duvernay Formation in Alberta, Canada may be predicted in wells lacking core control when class proportion and thickness conditions are met. Unsupervised machine learning technique, non-negative matrix factorization with k-means clustering (NMFk), automatically identifies reservoir significance, undetected through the traditional deterministic modelling, within the Duvernay Formation without calibration to core observations. The application of NMFk with petrophysical data may assist in highlighting intervals of interest in advance of core descriptions reducing observer inconsistency and bias and enhancing the quality and relevance of core description for reservoir correlation and mapping. Machine learning methods provide precise, consistent, and objective petrophysical interpretations and reservoir characterization, and increases the consistency and accuracy of resource assessment for petroleum exploration and production. Unsupervised machine learning and magnetotellurics are useful analytical tools to assess prospective geothermal resources in the Tularosa Basin of south-central New Mexico based on heat flow, temperature, porosity, and permeability. The unsupervised machine learning method, NMFk, identifies locations with the highest likelihood of geothermal success, and the passive geophysical method, magnetotellurics can detect subsurface geothermal prospects. The integration of NMFk and MT can provide a 3D assessment of heat flow, temperature, and permeability for geothermal exploration. This research provides innovative methods to aid in the development of efficient and cost-effective approaches for future energy exploration and production.
Applied forensic investigation of elevated arsenic levels in the Central Texas Trinity Aquifer system.
(2015-07-22) Kirby, Joshua Stephen, 1988-; Yelderman, Joe C.; Atchley, Stacy C.
A recent change in EPA regulation lowered the maximum contaminate limit (MCL) of arsenic in drinking water from 50 to 10 μg/l. Lowering the MCL has put numerous water systems in Texas over the limit. An arsenic “hot spot” is located in parts of Falls, Hill, Limestone, and McLennan counties and is an issue for suppliers. All suppliers having arsenic issues in this "hot spot" produce water from the Hosston Member of the Trinity Aquifer. Because the Trinity Aquifer is a deep, confined aquifer, arsenic is presumed to occur naturally. This study incorporates chemical analysis of raw groundwater, entry point water, geophysical well logs, and cuttings from wells in an attempt to determine the (1) distribution, (2) source, (3) environment of occurrence, and (4) potential stresses to the aquifer which would cause elevated arsenic levels.
Assessing the magnitude and frequency of hydrological processes and their effect on threshold channel morphology, North Bosque River, TX.
(2021-04-20) Barber, Samuel T., 1995-; Allen, Peter M., 1947-
The North Bosque River (NBR) is a dynamic fluvial system experiencing geomorphic change resulting from hydrological and sedimentological influences. This thesis describes the forces that influence hydrological and geomorphological shifts along the NBR corridor, emphasizing the relationship between the frequency and magnitude of high flow events. An increase in NBR mean daily discharge from 5.6 to 8.4 m3/s is attributed to a historical 100-yr flood recorded in late 1991. The NBR’s geomorphic response to flow increases are primarily observed as planform and slope profile changes. Vertical profile changes are limited by the presence of rigid beds, which degrade at a rate of 0.73 mm/yr. Planform erosional assessments indicate that NBR cutbanks are shearing at 0.5 to 0.75 m/y. The NBR’s slope increased and sinuosity decreased from 1995 to 2019. These morphological and hydrological changes characterize the NBR’s response to a historical flood event.
The Austin chalk and its petroleum potential : South-Central Texas
(2017-10-09) Thornhill, Stephen Alan; Baylor University. Dept. of Geology.
The Austin Chalk Formation (Upper Cretaceous) consists of uniformly bedded lithologies throughout south-central Texas. The lithologies found within the subsurface are technically wackestones to mudstones. These general textures may be divided into three specific facies: 1) Chalk Marl facies (1,000-7,500 feet), 2) Micritic Limestone (7,500-12,000 feet), and 3) Black calcarous shale facies (12,000 feet). The Chalk has been divided into four specific mappable units: 1) Lower Atco, 2) Upper Atco, 3) Bruceville Chalk Marl, and 4) Futchins Calk. The thickening trends of three units along with the total Austin Chalk interval suggest a uniform period of deposition during the Upper Cretaceous. The sediments deposited during this period were formed along a carbonate ramp-platform depositional environment. Structuring in south-central Texas is primarily faulting and fracturing trends and the homoclinal dip of Chalk to the southeast. The faulting planes are near vertical (65-70 degrees) and strike NE-SW. Fractures are oriented perpendicular to one another and are positioned NE-SW and NW-SE. Production potential of hydrocarbons within the Austin Chalk is controlled mainly by fracture development. Therefore, zones which intersect highly fractured areas are generally good producing wells. Giddings field and various fields within Gonzales County possess the largest amount of hydrocarbon production throughout the study area. Production is greatest in Lee County -- 27 million barrels (bbls) of oil and 75.5 billion cubic feet (BCF) of gas. The cumulative production along the productive chalk trend decreases in a southwesterly direction. This situation implies that fracture development will also show a decrease in this direction. Future development of the Austin Chalk is controlled by economic conditions. However, the best potential zones for future drilling sites may be indicated by "sweet spots" located on cumulative production maps.
Characterizing the reservoir quality of Marcellus Formation Mudrocks through a comparison of chemostratigraphic character and petrophysical response in north-central Pennsylvania.
(2017-11-02) Hanson, Jared J., 1988-; Dworkin, Stephen I.
This study combines robust geochemical data with core descriptions and wireline logs to gain new insight into the paleoceanographic conditions during Marcellus deposition and the resulting quality and distribution of reservoir facies. Three cores penetrating the Marcellus Formation in Pennsylvania were described and samples were taken at two-foot intervals. The geochemistry of the 502 samples was characterized and used to identify chemofacies. Lithofacies descriptions and chemofacies characterization indicate the production and preservation of TOC-enriched intervals occurred during periods of euxinia/anoxia coupled with high production. GR log response in the Marcellus Formation is principally controlled by uranium. The relationship of uranium to organic matter allows for the creation of synthetic TOC logs from GR logs and the prediction of TOC in wells lacking core control. Subsurface correlation indicates relative thinning of facies to the northwest and a general increase of organic enrichment thicknesses to the northeast of our study area.
Charcoal chemistry : developing a proxy for paleofire regimes.
(2013-09-16) Von Bargen, Justin M.; Hockaday, William C., 1979-; Geology.; Baylor University. Dept. of Geology.
Wildfires have occurred over geologic time since the evolution of land plants and affect global biogeochemical cycling and ecosystem processes. Charcoal particles in the geological record may contain information on several aspects of paleowildfire regimes. The fire intensity, the energy produced during a fire, is poorly understood for fires that occurred in the past. I propose that the organic chemical composition of charcoal may be used to approximate the fire temperature. To test this, I used 13C nuclear magnetic resonance (NMR) to quantify the carbon bonding environments in charcoal particles derived from specimens burned during a prescribed fire at the Lake Waco Wetland in Waco, Texas. I compared the NMR data for charcoal to fire temperatures measured by thermocouples and was able to predict the temperature within 89°C. The intrinsic relationship between pyrolysis temperature and charcoal structure may allow for a better understanding of past conditions during fires.
Chemostratigraphic analysis and petrophysical modeling of the Upper Jurassic Haynesville Shale in East Texas and West Louisiana.
(2016-11-21) Idleman, Erin E., 1990-; Dworkin, Stephen I.
The Haynesville Shale, a Late Jurassic, organic-rich marine shale found in east Texas and west Louisiana, is one of the most heavily developed shale-gas plays in the United States. This study integrates the geochemical data of core samples from three Haynesville wells, the Prescott Family 35 H 1 (API# 1701524594), Woolworth 25 H (API# 1701734753), and Rosborough 1 H (API# 4220334702), with petrophysical well logs and depositional facies to evaluate the controls on productivity and preservation of organic matter in the Haynesville Shale and to predict the most hydrocarbon-rich zones. The three cores were described and sampled to enable the evaluation of paleoceanographic conditions across the northernmost extent of the Haynesville Basin. Furthermore, petrophysical well-logs were compared to geochemical facies for correlative and predictive purpose. Reducing oceanic conditions and high productivity and burial rates all contribute to the preservation of organic-rich source rocks. However, through an integrated analysis of geochemical data, it is possible to conclude that high productivity, which drives high sedimentation and burial rates, results in the most organic matter preservation, rather than the traditional theory that deep water anoxia is the driving mechanism. Additionally, by using the relationship between geochemical character and petrophysical log response it is possible to identify the most organic-rich zones.
Climate and landscape reconstruction of the Arroyo Chijuillita Member of the Nacimiento Formation, San Juan Basin, New Mexico : providing environmental context to early Paleocene mammal evolution.
(2019-04-18) Davis, Adam James, 1989-; Atchley, Stacy C.
Sedimentologic, stratigraphic, and paleopedologic attributes of an outcrop of the lower Paleocene Arroyo Chijuillita Member (Nacimiento Formation) in the Bisti/De-Na-Zin Wilderness Area (San Juan Basin, New Mexico) are studied to provide paleoenvironmental context for the Puercan North American Land Mammal Ages (NALMA). The outcrop intersects the middle and late Puercan (Pu2-Pu3) age and is ideal to assess potential causes of this turnover. Fluvial channel and laterally continuous sandstones and associated fine-grained floodplain deposits, including paleosols documenting variability in drainage and maturity, comprise the outcrop. Paleoclimatic reconstructions from paleosols indicate no change in climate, and evidence of regional tectonics effecting deposition is not observed. Spatial and temporal variability in paleopedologic and sedimentologic characteristics are interpreted to be the result of autocyclic channel avulsion/migration. These observations suggest that mammalian turnover (Pu2-Pu3) is likely the result of rapid evolution following the K-Pg boundary and/or competition from migration of mammalian species into the basin.
Climatic and human influences on Holocene alluvial history and paleoenvironment of the middle Delaware River Valley, USA.
(2012-11-29) Stinchcomb, Gary E.; Driese, Steven G.; Nordt, Lee C.; Geology.; Baylor University. Dept. of Geology.
The potential for future prolonged drought episodes in the Northeastern USA is alarming given that a humid climate currently provides water to +50 million people in the northeast, USA. Hydro-climatic projections are hampered by a lack of regionally-based paleoenvironmental reconstructions. The middle Delaware River Valley provides a unique opportunity to expand the Holocene alluvial history and paleoenvironment for the northeast, USA. Thirty-six soil profile descriptions, 332 grain size analyses, and 82 14C ages from trenches and auger borings show that similar alluvial landforms within the river valley have different formation histories and depict a valley that has experienced middle to late Holocene floodplain and terrace reworking. Despite erosion, secular changes in buried soil and sediment properties are closely associated with climate change and land-use. A Holocene time-series was constructed using 149 δ13Csom values from alluvial terrace profiles. There is good agreement between increasing δ13Csom and Panicoideae phytolith concentrations, suggesting that variations in C4 biomass are a contributor to changes in the soil δ13C. A measurement error deconvolution curve over time reveals two isotope stages (II and I), with nine sub-stages exhibiting variations in average δ13Csom (%C4). Stage II, ~10.7-4.3 ka, shows above average δ13Csom (increase %C4) values with evidence of an early Holocene warm/dry interval (sub-stage IIb, 9.8-8.3 ka) that coincides with rapid warming and cool/dry abrupt climate change. Sub-stage IId, 7.0-4.3 ka, is an above average δ13Csom (increase %C4) interval associated with the mid-Holocene warm/dry Hypsithermal. The Stage II-I shift at 4.3 ka documents a transition toward below average δ13Csom (decrease %C4) values, coinciding with decreasing insolation and moisture budget reorganization. Sub-stages Ib and Id (above average %C4) coincide with the first documented occurrence of maize in northeastern USA and population increase during the Late Woodland. These associations suggest that humans influenced δ13Csom during the late Holocene. The influence of land-use is further corroborated by a regionally extensive anthropogenic sedimentation event documented throughout eastern North America, pre-Colonial sediment (PCS) circa: A.D. 1,100–1,600. These data demonstrate that combined prehistoric land-use and climate change impacted eastern North American floodplains several hundred years prior to the onset of European Settlement.
A comparison of the Cretaceous (Albian) Edwards Limestone bioherms of Central Texas with the Holocene Coral Reefs of Bermuda.
(2011-09-14) Damman, Adam J.; Bonem, Rena Mae.; Geology.; Baylor University. Dept. of Geology.
The Edwards Limestone of Central Texas is comprised of numerous rudist-dominated patch reefs that are collectively referred to as the Central Texas Reef Trend. These bioherms were protected by the Stuart City barrier reefs along the Texas Gulf Coast. The Stuart City reefs have been compared with the modern barrier reefs of Australia and Belize, but there is currently no modern analog for the Central Texas bioherms. Bermuda was chosen for a modern analog study based on the existence of a protective rim reef system, its low biodiversity, and a slower reef growth rate as compared with other modern reefs. Although the patch reefs of Bermuda were determined to be “similar” to the Central Texas Edwards Limestone bioherms in many respects, the high temperatures and unique oceanographic conditions of the Cretaceous likely means that no exact modern analog for the rudist-dominated Edwards bioherms exists.
Compartmentalization in the northern segment of the Brazos River Alluvium aquifer.
(2019-04-05) Jarvis, Jacob C., 1994-; Yelderman, Joe C.
Alluvial aquifers such as the Brazos River Alluvium aquifer in central Texas can contain locally significant amounts of groundwater that may be used for irrigation, domestic supply, or to mitigate stress applied to other groundwater and surface water resources. Alluvial aquifers occur within the alluvial valley of major rivers and are intrinsically connected to the stream. In order to properly manage groundwater uses in the Brazos River Alluvium aquifer, the dynamic relationship between the aquifer and the Brazos River needs to be understood. For the Brazos River Alluvium, the Brazos River is a gaining stream and influences groundwater flow through affecting the elevation of the water table and interacting with lateral and underlying bedrock boundaries. This study utilizes spatial analysis, sediment core, and field observations to characterize how the relationship between the Brazos River and bedrock boundaries of the aquifer may compartmentalize groundwater flow within the Brazos River Alluvium aquifer.
Controls on reservoir continuity and distribution within the Mississippian Pekisko Formation at Twining field, south-central Alberta, Canada.
(2007-02-06T23:10:25Z) Josson, Erika M.; Atchley, Stacy C.; Geology.; Baylor University. Dept. of Geology.
Twining field, located in south-central Alberta, Canada, and discovered in 1951, produces from the Mississippian Rundle Group. Estimates of original in-place oil are 913 million barrels, with 46 million barrels identified by the Alberta Energy Utilities Board as recoverable (5% recovery factor). Cumulative production to date from the Rundle Group at Twining is 31 million barrels (67% of recoverable reserves). The Pekisko Formation of the Rundle Group is a carbonate reservoir that is unconformably overlain by the Lower Cretaceous Mannville Group. Reservoir quality (porosity and permeability) is best developed in the shoal facies association contained within 9 shallowing-upward parasequence sets that are relatively continuous across the study area where they are not karst-modified or truncated beneath the basal Cretaceous unconformity.
Controls on the accumulation of organic matter in the Eagle Ford Group, Central Texas, USA.
(2014-01-28) Boling, Kenneth S.; Dworkin, Stephen I.; Geology.; Baylor University. Dept. of Geology.
The Upper Cretaceous Eagle Ford Formation is an organic rich marine mudrock which outcrops across central Texas. This study documents the chemostratigraphic character of the Pepper and Eagle Ford Formations in central Texas using major and trace elements, organic matter abundance, and the isotopic and stoichiometric character of organic matter. The chemical data allow the identification of six distinct chemofacies that are potentially useful for correlation purposes. Based on these data, changing paleoceanographic conditions were documented ranging from normal marine conditions associated with the Pepper Formation, anoxic conditions associated with the Lower Eagle Ford Formation, suboxic conditions associated with most of the upper Eagle Fords, and then a return to normal marine conditions at the top of the Eagle Ford Formation. The high TOC content of the lower Eagle Ford was most likely caused by high productivity which in turn drove conditions to anoxia.
Correlation of earthquakes with seismogenic faults along the Northern Arizona Seismic Belt, southwestern margin of the Colorado Plateau.
(2011-09-14) Lancaster, Daniel S.; Cronin, Vincent S.; Geology.; Baylor University. Dept. of Geology.
The Northern Arizona Seismic Belt (NASB) is one of the most seismically active areas in Arizona, and extends from near Kanab in southernmost Utah to the Mogollon Plateau south of Flagstaff, Arizona. The NASB defines the seismic boundary between the Colorado Plateau and the Basin and Range Provinces. This research attempts to spatially correlate four M≥4.0 earthquakes that had epicenters in the Kanab-Fredonia area of the NASB with the faults that might have generated them. Earthquakes were correlated spatially with mapped faults and distinct geomorphic lineaments within the West Kaibab fault system, which to the point has minimal documented evidence of late Neogene movement. Recognition of recent seismicity along the West Kaibab fault system is consistent with the hypothesis that Basin and Range extensional faulting is expanding into the Colorado Plateau.
Correlation of selected earthquakes with seismogenic faults, central Oklahoma.
(2016-02-29) Rasaka, Brandon M.; Cronin, Vincent S.
Hypocenter locations for over 3000 earthquakes of M≥2.0 in central Oklahoma between the years 2014 and 2015 were used to attempt to locate seismogenic faults near the city of Guthrie. Focal mechanisms from 29 earthquakes of M≥3.5 were analyzed using the Seismo-Lineament Analysis Method (SLAM). Focal mechanism solutions for these 29 events were projected as swaths on the ground surface represented by a digital elevation model (DEM). Within each swath the surface trace of a causative fault might be found if the nodal plane is coincident with the fault, the fault is emergent at the ground surface and is approximately planar. Analysis of the DEM within each swath revealed few geomorphic lineations that might be caused by fault movement associated with the earthquakes. It is inferred from these results and field work that the faults producing these earthquakes do not intersect the ground surface.

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