Master of Science (MS), Wright State University, 2024, Earth and Environmental Sciences

The Teays River Valley is an ancient river valley system that existed before the Pleistocene Ice Age and spanned present-day Illinois, Indiana, Ohio, West Virginia, and Virginia. During the Pleistocene Ice Age, the Teays River Valley was buried by advancing continental glaciers and meltwater throughout most of its length. Due to the Teays' average width of roughly 2 miles and burial depth of approximately 200 meters (656 feet), the Ohio Geological Survey has been pursuing geophysical methods to map the location and depth of the Teays River Valley in Ohio. The present study is a refraction analysis using the first breaks from a seismic reflection dataset from west-central Ohio across the potential location of the buried Teays Valley. The seismic refraction results display a bedrock topography similar to the original seismic reflection profile, having an estimated bedrock depth along the profile roughly ranging from 24 m (79 ft) to 213 m (699 ft) in the buried valley. The refraction survey indicated average bedrock velocities of 3956 m/s (~13000 ft/s) and depths ranging from about 80 to 700 feet (24 to 213 meters), which is consistent with the reflection results and with a valley fill of unconsolidated sand and clay and limestone bedrock.

Committee: Christopher Barton Ph.D. (Committee Chair); Ernest C. Hauser Ph.D. (Committee Co-Chair); Doyle Watts Ph.D. (Committee Member) Subjects: Geological; Geology; Geophysics

Master of Science (MS), Wright State University, 2015, Earth and Environmental Sciences

In July 2013, an industry-scale seismic reflection survey was conducted at a site in northern Jay County, Indiana, by geophysics students and faculty of Wright State University. As a part of that effort, a separate near-surface seismic dataset was collected to examine the Vp, Vs, and Poisson's Ratio of the glacial drift and upper bedrock. This near-surface study successfully used a common dataset that was separately analyzed for both Vp (seismic refraction) and Vs (MASW) to calculate the Poisson's Ratio of the glacial drift and underlying bedrock. The driller's log for a water well near the east end of this near-surface survey indicates glacial drift (unconsolidated clay and sand) overlies limestone bedrock at a depth of 110 feet. Water wells in the broader area show bedrock depth varying from 110 to 122 feet, but locally as much as 140 feet. The near-surface seismic data were acquired using a Bison EWG (Elastic Wave Generator) assisted weight drop source that shot every station through a stationary spread of 48 channels using a pair of 24-channel Geode seismographs. Each channel recorded a a single vertical 4.5 Hz geophone at a station spacing of 10 feet. Four weight drop records at each source point were summed to enhance the S/N ratio. The same data volume was processed both for Vs using SurfSeis3 MASW (Multichannel Analysis of Surface Wave) software and for Vp using IXRefrax3 refraction software. The MASW results suggest that the depth to bedrock at the survey location ranges from 115-120 feet (~35 m) with Vs of 1,200-2,000 ft/sec (366-610 m/s) for glacial drift and 2,400-2,700 ft/sec (730-823 m/s) for bedrock. The P-wave refraction results suggest the depth to bedrock ranges from 118-122 feet (36-37 m) with average Vp of ~5,000 ft/sec (1,524 m/s) for glacial drift and ~17,000 ft/sec (5180 m/s) for limestone bedrock. The Poisson's Ratio for the glacial drift calculated using the Vp and Vs at common locations in this study is 0.470-0.473, which i (open full item for complete abstract)

Committee: Ernest Hauser Ph.D. (Advisor); Doyle Watts Ph.D. (Committee Member); David Dominic Ph.D. (Committee Member) Subjects: Energy; Geophysical; Geophysics

Master of Science (MS), Wright State University, 2019, Earth and Environmental Sciences

This study focuses on northern Terre Haute, Indiana, where seven 2D seismic reflection time sections were collected by CountryMark and donated to Wright State University. Geologically, the area is on the eastern margin of the Illinois Basin. Two of these seismic lines display significant relief along a continuous, high-amplitude horizon approximately 180 milliseconds in two-way traveltime depth. This horizon was previously interpreted by CountryMark to be a Silurian reef core of the type common in this region of the Illinois Basin; however, other seismic lines within the data set display no relief. Furthermore, borehole logs within the area show no such relief at the equivalent depth of around 1700 feet. Therefore, the apparent structural high is an artifact within the two seismic lines, and can be called velocity pull-up. Various analyses were conducted to examine the causes of this velocity pull-up. The near-surface, within this region, contains many surfaces that may give rise to a velocity pull-up, including (1) the layer of weathered Pennsylvanian bedrock; (2) the Mississippian-Pennsylvanian Unconformity; and (3) an unconformity within Pennsylvanian section. It is possible that each of these surfaces could have enough relief to induce the observed velocity pull-up, and these possibilities were evaluated utilizing a combined analysis of Bouguer gravity, first-arrival traveltime tomography, passive seismic, and well log correlation. These multiple analyses show there is no Silurian reef core but a more complex velocity-inducing feature from a combination of the Mississippian-Pennsylvanian Unconformity and a shallower paleovalley fill.

Committee: Ernest C. Hauser Ph.D. (Committee Chair); Doyle R. Watts Ph.D. (Committee Member); David F. Dominic Ph.D. (Committee Member) Subjects: Geographic Information Science; Geology; Geophysical; Geophysics

Master of Science, University of Akron, 2014, Geology-Geophysics

Ground penetrating radar (GPR), electrical resistivity and seismic refraction surveys were used to image possible buried sinkholes and identify potential areas of subsidence in the shallow paleokarst surface of the Columbus Limestone at Ohio Caverns in Champaign County, Ohio. A buried sinkhole, incipient sinkholes and a possible buried cave passage spatially correlated with orthoimagery and surface evidence of subsidence. Correlations were established by using GIS software overlaying a structure-contour map of the paleokarst, as determined by GPR data, over orthoimagery of the area. Wenner and dipole-dipole electrical resistivity surveys suggest regions of lower resistivity surrounded by higher resistivity are associated with suspected subsidence. Refraction seismic data, collected along the same transect as the resistivity surveys, also correlated with an area of depression in the region of a suspected sinkhole. The seismic velocities from the refraction survey indicated lower depths for the clay soil and Ohio Shale contact and also the boundary between the Ohio Shale and the Columbus Limestone. Remote sensing using electrical resistivity, GPR and seismic refraction techniques successfully imaged the stratigraphy of the area and suggest other areas of incipient sinkhole formation.

Committee: David Steer Dr. (Advisor); John Peck Dr. (Committee Member); Ira Sasowsky Dr. (Committee Member) Subjects: Environmental Geology; Geographic Information Science; Geological; Geology; Geophysical; Geophysics

Master of Science, University of Toledo, 2007, College of Arts and Sciences

Although gravity and magnetic field data have been used to infer variations in the crustal structure of Ohio, seismic evidence regarding the depth to the Mohorovicic discontinuity is sparse. First arrivals from 13 regional earthquakes recorded by the Ohio Seismic Network between 2001 and 2006 were examined to investigate variations in crustal composition and thickness in Ohio and attempt to calculate the depth to the mantle. The average crustal structure consists of two layers: Paleozoic sedimentary rock over granitic crust (phase Pg) overlying the mantle (phase Pn). The average apparent P-wave velocities for the Paleozoic sedimentary rock and granitic crust are 4.8 km/s and 5.5 km/s respectively. Reduced travel time curves of first arrivals show nodirect evidence of a higher (~ 6.8 km/s) velocity lower crust (crustal phase Pb). Paleozoic sedimentary rock thickness, determined from well data, ranges from 700 m in western Ohio to over 4 km in southeastern Ohio. Calculated thicknesses of the Paleozoic sedimentary rock (-5.8 ± 8.8 km in western Ohio, 26.9 ± 25.8 km in southeastern Ohio) and granitic crust (20.1 ± 10.1 km in western Ohio, 57.6 ± 29.6 km in southeastern Ohio) beneath each station, determined from regional earthquake residuals (1.8 ±1.8 seconds early in western Ohio, 5.0 ± 5.4 seconds late in southeastern Ohio), have a mean value higher than thicknesses derived from well data and gravity and magnetic field interpretations. However, these results involve large standard deviations that span crustal models previously proposed. Comparing these thicknesses determined from regional earthquakes with thicknesses determined from teleseismic earthquakes and Earthscope Automated Receiver Survey (EARS) seismic data show small variations beneath most stations. Those stations with large variations between regionally, teleseismically, and EARS determined thicknesses also have a small number of regional earthquake observations.

Committee: Donald Stierman (Advisor) Subjects: Geology; Geophysics