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A magnetic study over a 95 m x 150 m area of the Hickory sandstone aquifer in central Texas was carried out as part of multitechnique geophysical investigation that included ground penetrating radar (GPR), electromagnetic (EM), seismic and seimoelectric. In geophysical exploration, the magnetic method can be utilized as an alternative to more expensive methods, such as seismic or it can be used to complement other methods. In this thesis, the magnetic method is applied to estimate the location of a previously mapped fault by Texas A&M geology students, and it is used to estimate the magnetic susceptibility contrast of the targeted fault. The main challenge of this study is imaging shallow faults using the geophysical magnetic method in a fractured aquifer with widely-scattered distribution of iron bearing rocks as in the case of the Hickory sandstone aquifer. A Geometric—G858 Cesium vapor magnetometer was used to collect magnetic data. The data consisted of 19 north-south and 1 east-west lines acquired in October and November of 2012. Elementary data processing such as diurnal correction, regional correction, reduction to pole (RTP) filter, Euler deconvolution, forward modeling and inversion were employed to characterize the faulted zone. This faulted zone separates granite basement rocks from the Hickory sandstone. As a result, this study emphasizes that Euler deconvolution applied to RTP-filtered data increases the interpretability of geological and structural contacts. The results of the magnetic method have been compared to results of GPR, EM and seismoelectric methods. Understanding the magnetic mineralogy of rocks and their properties can improve the geological interpretation of magnetic surveys.

Thesis (M. Eng.)--Carleton University, 2001. / Includes bibliographical references p. (115-117). Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of California, San Diego, 1997. / Vita. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains ix, 148 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 145-148).

Thesis (Ph. D.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 111-117). Also available on the World Wide Web.

The geological and geophysical knowledge about the northernmost part of Sweden has recently increased due to the Barents project, which includes acquisition of modern geophysical and geological information on behalf of the Swedish Geological Survey (SGU). During August 2013, a helicopter-borne versatile time domain electromagnetic (VTEM) survey was performed by Geotech Ltd, in the Soppero area northeast of Kiruna. From the VTEM measurements, a number of TEM anomalous zones have been identified and two of them are located south and southeast of the Lannavaara village. The main conductive features in the Lannavaara area can be explained by the presence of graphitic schist, which is spatially associated with a number of sulphide and iron oxide mineralisation occurrences. In this project, Maxwell thin sheet modelling and EM Flow conductivity-depth-imaging (CDI) software have been applied to selected anomalies in the Lannavaara area, for the purpose of extracting geometrical parameters of conductive features. This information has been used in order to confirm the structural framework of the area and evaluate the utility of VTEM measurements in this geological environment. In general, Maxwell thin sheet models of anomalies with small amplitudes show a better correlation with existing drill holes than models of anomalies with large amplitudes. The use of small amplitudes managed to confirm the structural model in the central part of the investigated area, which is an anticline. However, the use of different models and their distribution across the area is limited. Compared with Maxwell, CDIs from EM Flow provided a better way of confirming the general structural model in the area, although they include artefacts due to strong lateral gradients in conductivity. The Lannavaara area has also been investigated by VLF, Slingram and magnetic measurements and based on these data, multivariate analysis in SiroSOM reveals a strong correlation between VTEM and Slingram data, while VLF data appears to have much less or more complicated correlation with the other data sets. In summary, the results from the various software raise a question about the geological complexity in parts of the Lannavaara area, which may include multiple layers of graphitic schist, possibly expressed as smooth transitions in conductivity when represented by data from electromagnetic methods.

>Magister Scientiae - MSc / The fracture porosity and permeability of the Beaufort Seam 1 (BS1) and Ecca coal seams of the Waterberg Basin have been comprehensively characterised with the aid of geophysical wire‐line logs. The main aim of the thesis was to estimate the porosity and permeability of the coal seams using down‐hole wire‐line data; comparing results from injection falloff test to establish the validity of the technique as a fast an effective method. The study area is the largely under explored Karoo‐aged, fault bounded Waterberg basin Located in the Limpopo Province of South Africa. The study employed mainly the density and dual lateral resistivity logging data (Las format) from eight wells (WTB45, WTB48, WTB56, WTB58, WTB62, WTB65, WTB70 and WTB72). Density logging data was used for coal identification and fracture porosity estimation while fracture permeability was estimated from dual lateralog resistivity data. Analysis of fracture porosity required coal cementation indices and fracture width as an input parameter. These were estimated with the aid of water pump out test data, coal quality and gas analysis data provided by Anglo Coal in addition to the above mention logs. The collection of sheet coal model was used to represent anisotropic coal reservoirs with non‐uniform fracture system was used to represent these coals. The mathematical formulas used to estimate both fracture porosity and permeability took into account the above coal model. The theoretical formulas are a modification from both Darcy’s equation and Archie’s equations. The coal seams were encountered at depths ranging from 198m to 385m in the wells and were marked by low density and very high resistivity. From the estimated results the coal reservoirs are characterised by high cementation indices ranging from 0.82 to 2.42, very low fracture porosity and low fracture permeability. Estimated results show that coal reservoir fracture porosity ranged from 0.0002% to 0.33% for both BS1 and Ecca seams. Estimated results also show that coal reservoir permeability ranged from 0.0045mD to 6.05mD in the BS1 formation and from 0.01 to 0.107mD in the Ecca. Results when compared with those of injection falloff test shows that the estimated permeability is slightly lower as expected since the model did not account for coal anisopropy. The fracture permeability was found to decrease with increase in vitrinite content, coal rank, coal burial depth and increases with increase in inertinite content. On a basinal scale the model estimated permeability was found to increase slightly from the east to the west of the basin. The porosity decreases with increase cementation index for deeper coal seams and increases with increase cementation index for shallower coal seams.

The self-potential method responds to the electrokinetic phenomenon of streaming potential and has been applied in hydrogeologic and engineering investigations to aid in the evaluation of subsurface hydraulic conditions. Of specific interest is the application of the method to embankment dam seepage monitoring and detection. This demands a quantitative interpretation of seepage conditions from the geophysical data. To enable the study of variably saturated flow problems of complicated geometry, a three-dimensional finite volume algorithm is developed to evaluate the self-potential distribution resulting from subsurface fluid flow. The algorithm explicitly calculates the distribution of streaming current sources and solves for the self-potential given a model of hydraulic head and prescribed distributions of the streaming current cross-coupling conductivity and electrical resistivity. A new laboratory apparatus is developed to measure the streaming potential coupling coefficient and resistivity in unconsolidated soil samples. Measuring both of these parameters on the same sample under the same conditions enables us to properly characterize the streaming current cross-coupling conductivity coefficient. I present the results of a laboratory investigation to study the influence of soil and fluid parameters on the cross-coupling coefficient, and characterize this property for representative well-graded embankment soils. The streaming potential signals associated with preferential seepage through the core of a synthetic embankment dam model are studied using the forward modelling algorithm and measured electrical properties to assess the sensitivity of the self-potential method in detecting internal erosion. Maximum self-potential anomalies are shown to be linked to large localized hydraulic gradients that develop in response to piping, prior to any detectable increase in seepage flow through the dam. A linear inversion algorithm is developed to evaluate the three-dimensional distribution of hydraulic head from self-potential data, given a known distribution of the cross-coupling coefficient and electrical resistivity. The inverse problem is solved by minimizing an objective function, which consists of a data misfit that accounts for measurement error and a model objective function that incorporates a priori information. The algorithm is suitable for saturated flow problems or where the position of the phreatic surface is known. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The purpose of this study was to determine evacuation decisions of residents in Pinellas County, a vulnerable area in Florida, during Hurricane Irma in 2017, and whether those decisions will impact their future decisions to evacuate. This study also examines the resident’s perception of storm surge flooding during a hurricane. To understand evacuation decisions and storm surge perceptions a survey was conducted on residents in vulnerable areas of Pinellas County. The survey examined multiple aspects including the role of media, relationships, and sociodemographic status on decision making. Another aspect examined if their decision to evacuate for Hurricane Irma will impact their decision for the future. Residents were also asked to rate how different aspects of the storm influenced their decision, including flooding from storm surge. It was concluded that their decision to evacuate for Hurricane Irma will significantly impact their decision to evacuate for the next hurricane, with many residents claiming they would leave their local area. Storm surge was not perceived as the greatest threat, instead wind speed and size of storm were determined to be the greater threat. Better understanding of evacuation decisions and perceptions about storm surge can be used to update emergency management preparations and planning for the next hurricane.