Geophysics and Seismology Commons^™

Receiver Function Imaging Of Mantle Transition Zone Discontinuities Beneath Alaska, Haider Hassan Faraj Dahm

Doctoral Dissertations

"Subduction of tectonic plates is one of the most important tectonic processes, yet many aspects of subduction zone geodynamics remain unsolved and poorly understood, such as the depth extent of the subducted slab and its geometry. The Alaska subduction zone, which is associated with the subduction of the Pacific Plate beneath the North America plate, has a complex tectonic setting and carries a series of subduction episodes, and represents an excellent target to study such plate tectonic processes. Previous seismological studies in Alaska have proposed different depth estimations and geometry for the subducted slab. The Mantle transition zone discontinuities of …

Acquisition Of Active Multichannel Analysis Of Surface Waves (Masw) Data In Karst Terrain, Ghassan Salem Alsulaimani

Doctoral Dissertations

"This study was designed to verify the effects and data reproducibility when the length of receiver array, receiver spacing, source offset and array orientation parameters are changed for data acquired using multichannel analysis of surface waves (MASW), at intended target depth of 30ft (9m), and to compare the results with electrical resistivity tomography (ERT) data obtained for the same study site.

The MASW data acquired for 34 sites, along four profiles for each site using variable source offsets of 10ft (3m) and 30ft (9.1m), and variable receiver spacings of 2.5ft (0.76m) and 5.0ft (0.76m), concurrently. Out of the 272 profiles …

Integrated Geophysical Approach Using Electrical Resistivity Tomography And Multichannel Analysis Of Surface Wave In Assessing Wilson Spring Development, Ibrahim E. Ahmed

Doctoral Dissertations

"This research investigated fractured zones leading to preferential flow paths of Wilson Spring. In this context, electrical resistivity tomography (ERT) data and multi-channel analyses of surface waves (MASW) data were acquired at studied site with the purpose of mapping a variable depth to top of bedrock and geological structures.

Interpretation of the boreholes, MASW, and ERT data indicated that a depth to top of rock does vary significantly at the studied site due to many solution-widened fractures. Multiple near-vertical solution-widened fractures were mapped in the studied site based on the interpretation of the ERT data. The mapped solution-widened fractures appear …

Assessment Of Highway Condition Using Combined Geophysical Surveys, Abdallah Alhadi Dera

Doctoral Dissertations

"Four pavement sections were investigated using ground penetrating radar (GPR) and Ultrasonic Surface Wave (USW). The objective of this research was to compare the effectiveness of two non-destructive geophysical tools, GPR and the PSPA, in assessing the condition of the pavements, composed of different construction materials. The GPR data were acquired using a 1.5 GHz antenna along five traverses spaced at two ft. intervals approximately 1000 ft. long. On the other hand, the PSPA data were acquired at the stations spaced at 1000 ft. along the five GPR traverses. Core samples were collected at each site to constrain the interpretation …

Azimuthal Anisotropy Beneath North Central Africa From Shear Wave Splitting Analysis, Awad Abdussalam Henish Lemnifi

Doctoral Dissertations

"This study represents the first multi-station investigation of azimuthal anisotropy beneath the interior of north central Africa, including Libya and adjacent regions, using shear wave splitting (SWS) analysis. Data used in the study include recently available broadband seismic data obtained from 15 stations managed by the Libyan Center for Remote Sensing and Space Science, and those from five other stations at which data are publicly accessible. A total of 583 pairs of high-quality SWS measurements utilizing the PKS, SKKS, and SKS phases demonstrate primarily N-S fast orientations with an average splitting delay time of approximately 1.2 s. An absence of …

Geophysical Imaging Of Karst Features In Missouri, Jeremiah Chukwunonso Obi

Doctoral Dissertations

"Automated electrical resistivity tomography (ERT) supported with multichannel analysis of surface waves (MASW) and boring data were used to map karst related features in Missouri in order to understand karst processes better in Missouri. Previous works on karst in Missouri were mostly surficial mapping of bedrock outcrops and joints, which are not enough to define the internal structure of karst system, since most critical processes in karst occur underground. To understand these processes better, the density, placement and pattern of karst related features like solution-widened joints and voids, as well as top of bedrock were mapped. In the course of …

Methodology Investigations For Shear Wave Splitting Analysis, Fansheng Kong

Doctoral Dissertations

"Over the past several decades, shear wave splitting analyses have been increasingly utilized to delineate mantle structure and probe mantle dynamics. However, the reported splitting parameters (fast polarization orientations and splitting times) are frequently inconsistent among different studies, partially due to the different techniques used to estimate the splitting parameters. Here the study conduct research on methodology investigations for shear wave splitting analysis, which are composed of two sub-topics, i.e., a systematic comparison of the transverse minimization (TM) and the splitting intensity (SI) techniques and applicability of the multiple-event stacking technique (MES). Numerical experiments are conducted using both synthetic and …

Seismic Anisotropy And Mantle Dynamics Beneath The Central And Western United States, Bin Yang

Doctoral Dissertations

"Various tectonic features and the recent availability of high-quality broadband seismic data from the USArray and other seismic stations in the central and western United States (CWUS) provide a distinct opportunity to test different anisotropy-forming mechanisms. For the first part of the study, a total of 4138 pairs of well-defined shear wave splitting (SWS) parameters observed at 445 stations on the northern Great Plains show systematic spatial variations of anisotropic characteristics. Azimuthally invariant fast orientations subparallel to the absolute plate motion (APM) direction are observed at most of the stations on the Superior Craton and the southern Yavapai province, indicating …

Palynological Studies Of Holocene Lake Sediments In The Missouri Ozarks, Robert D. Haselwander

Doctoral Dissertations

"Five small lakes in southeast Missouri (Frisco, Pine Forest, and Bray Area lakes [Phelps County], and Cypress and Blue ponds [Bollinger County]) were cored for paleolimnological studies. Cores were evaluated for their sedimentology, palynology, and geochemistry. In two of these lakes (Bray Area and Pine Forest lakes) the planktonic algae were also studied in the water column, along with ecological parameters. Algae in the sediments were compared to algae in the water to understand the resistance of different species to decay, and a suggested methodology for this work is described. Reconstructions of the past environments around each lake were created …

Identifying Shallow Subsurface Stratigraphy And Voids Using Dispersive Characteristics Of Electromagnetic And Surface Waves, Payman Hajiani

Doctoral Dissertations

"This dissertation presents the results of three manuscripts on spectral analysis of electromagnetic and seismic surface waves to detect subsurface stratigraphy and voids. In the first manuscript, a new technique was developed by utilizing spectral analysis of surface waves to detect subsurface openings. This technique applied the concept of group delay to evaluate the effects of subsurface voids on the phase shift domain. Seismic data sets were acquired at different sites where the shape, size, and depth of the void varied. In all surveys, the time delay technique precisely identified the locations of the subsurface openings. The second manuscript presents …

The Role Of Pre-Existing Basement Fabrics In The Initiation Of Continental Rifting: The Okavango Rift Zone, Botswana, Angelica Alvarez Naranjo

Doctoral Dissertations

"Integrated geophysical, remote sensing, and field investigations of the Okavango Rift Zone (ORZ), Botswana indicate that a feedback between optimum-oriented basement structures and fluid flow influence the nucleation and growth of continental rifts in their incipient stages. The ORZ, the youngest rift of the East African Rift System, occurs within a Proterozoic inter-cratonic suture zone - the NE-trending Precambrian Damara/Ghanzi-Chobe orogenic belts. The Pleistocene to Holocene ORZ forms a ~450 km long and ~100 km wide half-graben bounded by NE-trending normal faults. Basement units within the Damara/Ghanzi-Chobe orogenic belts exhibit a well-developed NE-trending linear fabric (045-065) defined by parallel limbs …

Mineral And Geochemical Attributes Of The Midcontinent Rift Sequence; An Application For Deep Carbon Dioxide Sequestration, Alsedik Mohamed Ali Abousif

Doctoral Dissertations

"The potential for using the Oronto Group of the Midcontinent Rift (MCR) Sequence for CO₂ sequestration has been disparaged because of low porosity-permeability characteristics, which are largely a result of extensive calcite cementation. This study investigated the potential for using the MCR as a target for CO₂ sequestration by examining reactions involving detrital host-rock minerals at high pressure-temperature conditions that could provide dissolved Ca²⁺, Mg²⁺, and Fe²⁺, and then precipitating these cations as carbonate minerals. The effect of carbonic acid on cement dissolution was also evaluated with respect to enhancing porosity and …

Shear Wave Splitting Analysis Beneath Tien Shan: Geodynamic Implications Of Complex Anisotropy, Solomon Gerra Cherie

Doctoral Dissertations

"In spite of numerous studies, the mechanisms for the crustal shortening, mountain formation and associated tectonism leading to complex or simply seismic anisotropy formation beneath the Tien Shan Orogenic Belt is still debated. The most popular hypotheses suggested for the existence of seismic anisotropy are small-scale mantle convection, regional scale resistive basal shear and APM induced asthenospheric flow. Here, we used shear-wave splitting (SWS) measurements with good azimuthal coverage to provide additional constraints on the various models proposed by previous studies. One of the most effective approaches utilized to constrain convective mantle flow patterns is the splitting of P-to-S converted …

Origin And Stratigraphic Architecture Of The Middle Permian Lower And Upper Quanzijie Low-Order Cycles, Bogda Mountains, Nw China, Jonathan Obrist-Farner

Doctoral Dissertations

"This study is carried out in the Bogda Mountains, NW China, and aims to provide a detailed sedimentary, stratigraphic, environmental, and paleoclimatic reconstruction in the paleo-mid-latitude along the east coast of Pangea. The Middle Permian lower and upper Quanzijie low-order cycles (QZJ LCs) provide a nearly complete sedimentary record in an area were little is known. In the first part of this work, the previously-established QZJ LC is divided into two LCs on the basis of regional stratigraphic correlation and major changes in depositional environments and tectonic and climatic processes. The newly-established lower QZJ LC is mainly composed of meandering …

Seismological Investigation Of The Okavango Rift, Botswana, Youqiang Yu

Doctoral Dissertations

The mechanisms of rifting have been intensively investigated using geological and geophysical techniques beneath mature rift zones. However, current understanding on the earliest stages of rifting is seriously limited. Here we employ recently archived data from 17 broadband seismic stations traversing northern Botswana to conduct the first shear wave splitting and mantle transition zone (MTZ) studies within the Okavango Rift Zone (ORZ). The ORZ is an incipient continental rift situated at the terminal of the southwestern branch of the East African Rift System. The resulting normal MTZ thickness and consistently rift-parallel fast polarizations imply an absence of significant thermal anomalies …

Precambrian Evolution Of The Salalah Crystalline Basement From Structural Analysis And 40Ar/39Ar Geochronology, Hanadi Abulateef Al-Doukhi

Doctoral Dissertations

"The Salalah Crystalline Basement (SCB) is the largest Precambrian exposure in Oman located on the southern margin of the Arabian Plate at the Arabian Sea shore. This work used remote sensing, detailed structural analysis and the analysis of ten samples using ⁴⁰Ar/³⁹Ar age dating to establish the Precambrian evolution of the SCB by focusing on its central and southwestern parts. This work found that the SCB evolved through four deformational events that shaped its final architecture: (1) Folding and thrusting event that resulted in the emplacement of the Sadh complex atop the Juffa complex. This event resulted …

Crustal Thickness And Vp/Vs Beneath The Western United States: Constraints From Stacking Of Receiver Functions, Uranbaigal Purevsuren

Doctoral Dissertations

"This study investigates crustal characteristics beneath the western United States. Crustal parameters, including crustal thickness (H), mean Vp/Vs, and the sharpness of the Moho as quantified by the amplitude of the P-to-S converted phases from the Moho, are measured at a total of 1000 permanent and portable broadband seismic stations using over 150,000 receiver functions recorded between 1988 and 2012. The study area is composed of a diverse set of tectonic provinces formed by a series of tectonic events, and is thus ideal for investigating crustal formation and modification by different tectonic processes. The resulting crustal thickness varies from …

Seismic Anisotropy And Mantle Flow Beneath Africa And Arabia, Ahmed Abdalla Elsheikh

Doctoral Dissertations

"In spite of numerous studies, the mechanisms for the rifting, uplifting, and volcanism on the African plate remain enigmatic. The most popular hypotheses proposed for explaining these tectonic phenomena involve edge-driven small-scale mantle convection and the thermal or dynamic effects of one or more mantle plumes. In this study we use continental scale shear-wave splitting (SWS) measurements to provide additional constraints on the various models of rifting, uplifting, and volcanism of the Cameroon Volcanic Line (CVL) and the Arabian plate. The splitting of P-to-S converted phases at the core-mantle boundary on the receiver side (XKS including PKS, SKKS, and SKS) …

Biomineralization Of Carbonates In Modern Microbial Sediments And Its Implications For Co₂ Sequestration, Varun Gnanaprian Paul

Doctoral Dissertations

"Several bacterial species influence carbonate mineral precipitation by modifying pH, alkalinity, Ca²⁺ activity and by providing nucleation sites for mineralization. Two studies have been undertaken to explore microbial influence in the mineralization of carbonates. In the first study, the ability of sulfate-reducing bacteria (SRB) to induce carbonate mineralization was investigated as a means to enhance mineral sequestration of CO₂. Sulfate-reducing bacteria enriched from hypersaline Storr's Lake, The Bahamas; Lake Estancia, New Mexico; and Great Salt Plains Lake, Oklahoma, were tested in reactors under varying CO₂ concentrations. Carbonate mineral precipitation was achieved only in reactors with Lake Estancia SRB community and …

Geochemical And Isotopic Characterization Of Lead In Fugitive Dust From Unsurfaced Roads In Missouri, Emitt C. Witt

Doctoral Dissertations

"Eighteen unsurfaced roadways in Missouri's rural Ozark region were sampled to characterize the differences in trace element and isotopic chemistry to determine if there is a human health concern with inhaling and/or ingestion of fugitive dust generated by a moving vehicle. Road reaches were selected to represent those in similar rural areas with and without the presence of mining activity--13 roads were selected in the Viburnum Trend (VT) resource mining area and five were located to the southwest of the mining areas. Samples were collected using a novel cyclonic fugitive dust sampler (patent pending) that collects a composite sample from …

Palynology Of Acid-Saline Lakes Of Western Australiabiostratigraphy And Paleoenvironmental Reconstruction, Carlos A. Sanchez Botero

Doctoral Dissertations

"Lakes are excellent repositories of fossils and sedimentary features that provide clues to past climatic and geologic events. Sediments from four cores drilled in Lake Aerodrome (LA1-09, LA2-09) and Lake Brown (LB1-09, LB2-09), two of the hundreds of ephemeral lakes in southern Western Australia, were analyzed for their palynological contents to understand the geologic and climatic evolution of the depositional basin. Palynofacies assemblages defined by statistical analyses of dispersed organic matter suggested differences in the depositional conditions and probable correlations between Lake Aerodrome cores. Detailed identifications and quantification of organic-walled microfossils yielded two palynomorph assemblages that reflect a climatic turnover: …

Mantle Flow And Lithosphere-Asthenosphere Coupling Beneath The Southwestern Edge Of The North American Craton: Constraints From Shear-Wave Splitting Measurements, Hesham A. Refayee

Doctoral Dissertations

"High-quality broadband seismic data recorded by the USArray and other stations in the southwestern United States provide a unique opportunity to test different models of anisotropy-forming mechanisms in the vicinity of a cratonic edge. Systematic spatial variations of anisotropic characteristics are revealed by 3027 pairs of splitting parameters measured at 547 broadband seismic stations. The western and southern edges of the North American craton show edge-parallel fast directions with larger-than-normal splitting times, and the continental interior is characterized by smaller splitting times spatially consistent fast directions that are mostly parallel to the absolute plate motion direction of North America. Except …

Plate Kinematics Of The Afro-Arabian Rift System With An Emphasis On The Afar Depression, Helen Carrie Bottenberg

Doctoral Dissertations

This work utilizes the Four-Dimensional Plates (4DPlates) software, and Differential Interferometric Synthetic Aperture Radar (DInSAR) to examine plate-scale, regional-scale and local-scale kinematics of the Afro-Arabian Rift System with emphasis on the Afar Depression in Ethiopia. First, the 4DPlates is used to restore the Red Sea, the Gulf of Aden, the Afar Depression and the Main Ethiopian Rift to development of a new model that adopts two poles of rotation for Arabia. Second, the 4DPlates is used to model regional-scale and local-scale kinematics within the Afar Depression. Most plate reconstruction models of the Afro-Arabian Rift System relies on considering the Afar …

Crustal Structure And Evolution Beneath The Colorado Plateau And The Southern Basin And Range Province, Lamuail Bashir

Doctoral Dissertations

"Stacking of about 15,500 P-to-S receiver functions recorded at 72 USArray and other broadband seismic stations placed on the Colorado Plateau and the SBRP in Arizona revealed systematic spatial variations in crustal Vp/Vs, crustal thickness and amplitude of P-to-S converted phases. Our results reveal that the BRP is characterized by a thin crust (28.2 ± 0.5 km), a mean Vp/Vs of 1.761 ± 0.014 and a mean amplitude (R) of P - to - S converted wave (relative to that of the direct P wave) of 0.181 ± 0.014 that are similar to a typical continental crust, consistent with the …

Applied Palynology: Multidisciplinary Case Studies From Egypt, Gulf Of Mexico And Usa, Mohamed K. Zobaa

Doctoral Dissertations

"Various applications of palynology have been used to study case studies from four different parts of the world, namely northern Egypt, offshore Gulf of Mexico, eastern Tennessee (USA), and New Orleans, Louisiana (USA). In these case studies, palynomorphs (spores, pollen, dinoflagellate cysts, and algae) have been utilized to define zones of hydrocarbon potential, reconstruct paleoenvironmental and paleoclimatic conditions, constrain the ages of the studied rock sequences, and express its potential as a replacement proxy for some expensive organic geochemical analyses. The ability to detect past hurricane activities and their associated damage to the geologic record is here presented as a …

Receiver Function Studies Of Crustal Structure, Composition, And Evolution Beneath The Afar Depression, Ethiopia, Sattam A. Almadani

Doctoral Dissertations

"The dissertation utilizes a set of sophisticated computer programs developed at the Geophysics group at Missouri S&T to characterize crustal properties beneath the Afar Depression in Ethiopia where extensional tectonics dominates. In this study, measurements of crustal thickness (H), crustal mean Vp/Vs [which is related to Poisson's ratio (Σ)], and the sharpness of the Moho (R) were determined using teleseismic data from 18 broadband seismic sensors that we deployed along a profile of 250 km long with a station spacing of ~ 10 km. The stations had been recording continuously for an entire year from December 2009 until December 2010. …

A Geological And Geophysical Study Of The Tendaho Graben In The Afar Depression, Ethiopia: Insights Into Transitional Continental Rifting, David Lee Bridges

Doctoral Dissertations

"A detailed magnetic and gravity study across the Tendaho Graben (the Red Sea propagator within the Afar Depression, Ethiopia) revealed features that can best be interpreted as a continental rift undergoing oceanization. This NW-trending extensional structure is ~50 km wide and it is confined within well-developed NW-trending boarder faults that deform the 2 km thick and ~ 2 Ma basaltic flows of the Afar Stratoids. The age of the basaltic flows becomes progressively younger inward from the boarder faults until it reaches ~30,000 years close to the rift axis. The central part of the Tendaho Graben is characterized by a …

Two New Spline-Based Methods And Real Data Applications: High-Resolution Receiver Function Calculations From Teleseismic Broadband Waveforms And High-Accuracy Practical Potential-Field Integral Transformations, Bingzhu Wang

Doctoral Dissertations

"While receiver function (RF) calculation is fundamentally important and widely used, it is not well solved due to unstable deconvolution. A spline-based RF calculation method was proposed and it is demonstrated that both individual RFs and the stacked RF calculated with the spline method have sharper peaks than those with the water-level spectral division method and the iterative deconvolution method. At the common peaks on the stacked RFs, there are close similarities for all three RF calculation methods. The better calculated RFs with the spline method lead to improved H - K analysis and improved determination of the optimal Moho …

Apparent Weekly And Daily Earthquake Periodicities In The Western United States, And Evolution Of Wadi Kubbania In Egypt, Ali Hadi Atef

Doctoral Dissertations

"The dissertation consists of two separate sections. The first section is on apparent daily and weekly periodicities in earthquake occurrence in the western United State [sic]. Analysis of Apparent Seismicity Rate (ASR) in the western United States confirmed the existence of prominent spectral peaks with a period of 1 and 7 days. The number of recorded earthquakes on Sundays for the duration of 1963-2008 is about 5% higher than that on weekdays, and, more significantly, there is a 9% increase of ASR in the early morning compared with that in the middle of the days. Significant similarities between the spatial …

Ground Penetrating Radar Investigations In Upper Kama Potash Mines, Oleg N. Kovin

Doctoral Dissertations

"An understanding of the structure and state of the rock mass surrounding underground openings in the potash mines is critically important for safe mining, planning the methods of extraction of an orebody, and preventing the influx of ground water. Continuous common offset ground penetrating radar (GPR) data were acquired in the potash mine operated by the Joint Stock Company (JSC) "Silvinit" (Russia) as part of an investigation of both pre-existing fractures exposed by mine workings and other anomalous geological structures. During the course of GPR investigation, the electrical properties of salt-bearing units were determined, site-specific data acquisition techniques and object-oriented …