Tomography is an imaging technique to develop a representation of the internal features of material using a penetrating wave, such as an electromagnetic wave. The calculation method used is an example of an inverse problem, which is a system where the input and the output are known but the internal parameters are not. These parameters can be estimated by understanding the responses of a penetrating wave as it passes through the unknown media. A forward problem is just the opposite; the internal structure and input penetrating wave is known and the output is determined. For both forward and inverse problems, raytracing is needed to define the raypath through the medium and inversion techniques are used to minimize the error for a discretized matrix of material properties. To assess various inversion techniques for use in shallow karst conditions, three synthetic karst geology models, each with increasing complexity, were generated. Each model was analyzed using forward modeling techniques to compare the calculated tomograms from known geometry and material properties. Gaussian Raytracing with LSQR inversion technique performed the best. This technique, Gaussian Raytracing with LSQR, was then applied to an inversion problem; cross-borehole ground penetrating radar data was collected at a karst geology field site and tomograms were produced. The resulting tomography confirmed information detailed in the driller's logs and features between boreholes were identified. This confirmed that cross-borehole ground penetrating radar is an applicable technique for use in geotechnical site characterization activities in karst areas.

Pendant une éruption volcanique sur des sommets englacés, des coulées de débris syn-eruptifs,dénommées lahars, peuvent être générées par la fonte partiale de glaciers. Ce phénomène estbien connu sur le volcan Cotopaxi, Equateur. La présente étude concerne trois vallées et un cônede déjection sur le flanc sud-ouest de ce volcan. Une première analyse a été conduite par relevésde formes géomorphologiques dans ces vallées qui témoignent des processus d’érosion et desédimentation lors du passage de lahars dans le passé, notamment ceux du dernier événementéruptif datant de 1877 AD. Bien que les types des formes géomorphologiques déterminées sontles mêmes, leur distribution spatiale varie d’une vallée à l’autre en fonction d’une interaction deparamètres morphologiques locaux. Les conditions environnementales individuelles déterminentégalement le volume de l’écoulement, paramètre crucial dans la délimitation de zones de risques delahars dans les plaines adjacentes. Pour cela, une deuxième étude a été menée à grande échelle surle cône de déjection à l’exutoire de la vallée la plus au Sud des trois. Une analyse intégrale de la morphologiede surface et des affleurements naturels a été complétée par des données stratigraphiquesde subsurface obtenues via un sondage avec un Géoradar. Reconstituer l’architecture sédimentairede ce cône permet de visualiser la distribution spatiale de formes érosives et de dépôts. L’étude àrévélé que différentes parties du cône sont actives à des moments distincts et les épaisseurs dedépôts de lahars sont variables en fonction du type d’écoulement et de son volume. Ceci permetde relier les dynamiques géomorphologiques des plaines alluviales aux zones d’initiation de laharssur les flancs du volcan. Enfin, cette étude a débouché sur la mise en place d’une nouvelle fonctiondans le logiciel de modélisation de lahars LAHARZ prenant en compte l’incorporation progressive desédiment dans un contexte érosif dans les vallées, ce qui permet une meilleure délimitation de zonesde risque de lahars sur le cône. / During a volcanic eruption at ice capped volcanoes, syn-eruptive volcanic debris flows, lahars, canbe triggered through the partial melting of the glaciers. This phenomenon is well known to have happenedat Cotopaxi volcano, Ecuador, where the present study has been realized. The latter concernsthree drainages on the southwestern flank of the volcano and one alluvial fan. A first analysis hasbeen conducted assessing geomorphologic features in the drainages testifying from erosional anddepositional processes during past lahars, in particular of those generated during the last eruptiveevent dating back to 1877 AD. Although the types of determined geomorphologic features are thesame, their spatial distribution varies among the three valleys as a function of an interplay of localmorphologic parameters. The individual environmental conditions determine also the flow volumeof such lahars, a critical parameter when to delineating hazard zones in the adjacent lowlands. Thesecond analysis has therefore be performed at large scale on the alluvial fan forming at the mouthof the southernmost of the three drainages. An integral study of the surface morphology and naturalexposures was enriched with subsurface stratigraphic information obtained through a ground penetratingradar survey. The sediment architecture of the fan provides valuable insights on the distributionof erosional features and deposits. Different fan parts appear to be active at different times andlahar deposit thicknesses are highly variable as a function of flow type and volume. This allows torelate floodplain dynamics to the initiation zone of lahars on the upper flanks of the volcano. At last,this research led to integrate a new bulking function acknowledging for erosional processes in thevalleys into the lahar-modeling software LAHARZ allowing to better delineate lahar hazard zones onthe fan.

The aim of this thesis has been to investigate the benefits, pitfalls and possibilities of using geophysical methods in archaeological projects. This is exemplified by surveys carried out at archaeological sites in different geographical and chronological contexts. The thesis also aims at investigating the cause for the under-use of the methods in Swedish archaeology by looking at previously conducted surveys. The methods used during these surveys have been Ground-penetrating radar (GPR), magnetometer, slingram and a kappameter. The surveys in the mountain tundra region of Lapland show that magnetic susceptibility surveys is a valuable aid in discovering heaps of fire-cracked stones and when combined with magnetometry, also hearths. GPR and magnetometer surveys within the Migration Period ringfort Sandbyborg provided the spatial layout of the fort and indicated, along with results from recent excavations and metal detections, many similarities with the ringfort Eketorp II. The non-magnetic character of the sedimentary bedrock on Öland and Gotland is suitable for magnetometer surveys and the method is also highly appropriate for the detection of the remains of high-temperature crafts. GPR surveys at St. Mary’s Dominican convent in Sigtuna produced the spatial layout of the central cloister area. The investigations also show that the geology, pedology, land use and the character of commonly occurring prehistoric remains in Sweden, in certain circumstances and in certain areas, have restricted the possibility of successfully carrying out geophysical surveys. Care must therefore be taken to choose the right instrument for the survey and to tailor the sampling density of each geophysical survey, according to the character and size of the expected archaeological remains, in order to maximize their information return. To increase the use of geophysical methods in Sweden the educational opportunities, both for surveyors and professional archaeologists, need to improve. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Manuscript.</p>

Ground penetrating radar (GPR) systems are increasingly being used for the detection and location of buried objects within the upper regions of the earth’s surface. The antenna is the most critical component of such a system. This thesis presents a comprehensive study of resistor-loaded planar dipole antennas for GPR applications using both theory and experiments. The theoretical analysis is performed using the finite difference time domain (FDTD) technique. The analysis starts with the most popular planar dipole, the bow-tie. A parametric study is done to find out how the flare angle, length, and lumped resistors of the antenna should be selected to achieve broadband properties and good target detection with less clutter. The screening of the antenna and the position of transmitting and receiving antennas with respect to each other and ground surface are also studied. A number of other planar geometrical shapes are considered and compared with the bow-tie in order to find what geometrical shape gives the best performance. The FDTD simulations are carried out for both lossless and lossy, dispersive grounds. Also simulations are carried out including surface roughness and natural clutter like rocks and twigs to make the modeling more realistic. Finally, a pair of resistor-loaded bow-tie antennas is constructed and both indoor and outdoor measurements are carried out to validate the simulation results. / <p>QC 20100923</p>

The terms &lsquo / ground-probing radar&rsquo / , &lsquo / ground penetrating radar (GPR)&rsquo / , &lsquo / sub-surface radar&rsquo / or &lsquo / surface-penetrating radar (SPR)&rsquo / refer to various techniques for detecting and imaging of subsurface objects. Among those terms GPR is preferred and used more often. In this thesis, the depth and the position of the buried circular cylinder are determined by a GPR system which comprises of an optical fiber sensor (OFS). The system is a combination of OFS, GPR and optical communication link. In order to determine the depth and the position, first of all the electric field distribution at the OFS is obtained by integrating the Green&rsquo / s function over the induced current distribution. Those distributions are observed for different frequency and depth values. The voltages inside the distribution are measured by OFS. By changing the depth of the cylinder and the frequency of the system, various plots showing x axis displacement versus measured voltages are obtained. Those plots are related to interference fringe patterns. The position and the depth of the cylinder are obtained using interference fringe patterns. All of the studies mentioned are performed in MATLAB R2007b program. The noises of the system due to OFS are extracted using OPTIWAVE OPTISYSTEM 7.0 program. By adding those noises to the measured voltage values, the operating frequency of the system is observed.

Rock glaciers play a significant role in the alpine debris transport system. For practical and engineering considerations, identifying the internal structure and its relationship to surface characteristics is significant in terms of how a rock glacier settles during periods of melting, and the mode of deformation. A better understanding of these factors is important for engineers, engineering geologists and geomorphologists who must make prudent evaluations of rock glaciers as potential sites for human development and uses. It is equally important for evaluating potential stores for water on other planets such as Mars. Ground penetrating radar (GPR) shows that the internal structure of a lobate rock glacier located in the San Juan Mountains of southwest Colorado consists of continuous to semi-continuous horizontal layers of ice-supersaturated sediments and coarse blocky rockslide debris which likely formed through catastrophic episodes of rockfall from the cirque headwall. Folds in the uppermost layers correspond to the surface expression of ridges and furrows, indicating that compressive stresses originating in the steep accumulation zone are transmitted downslope through the rock glacier. The rock glacier is a composite feature that formed by a process involving the development and overlap of discrete flow lobes that have overridden older glacial moraine and protalus rampart materials. The latter materials have been incorporated into the present flow structure of the rock glacier. The discovery of rock glacier-like features on Mars suggests the presence of flowing, or once-flowing ice-rock mixtures. These landforms, which include lobate debris aprons, concentric crater fill and lineated valley fill, hold significant promise as reservoirs of stored water ice that could be used as fuel sources for human exploration of Mars and provide a frozen record of the climatic history of the planet. To this end, the rock glacier in this study was used as a surrogate for similar Martian landforms. Liquid water, found to be abundant in this rock glacier, occurs within a network of interconnected channels that permeate throughout the landform. In terms of water storage within Martian analogs, consideration must include the possibility that some water ice may be stored in relatively pure form within lenses and vein networks that are supplied by seasonal frost accumulation and/or water influx from below.

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This dissertation details the design and development of a mobile autonomous platform from which to conduct a 3D ground-penetrating radar survey. The system uses a three-rover multiagent team to perform a site-selection activity during a lunar analog mission. The work took place beginning in 2008 and culminated in a final field test on Mauna Kea in Hawaii. This demonstration of autonomous acquisition of 3D ground-penetrating radar in a space robtic application is promising not only for in-situ resource utilization, but also for the concept of multiagent teaming.

This dissertation details the design and development of a mobile autonomous platform from which to conduct a 3D ground-penetrating radar survey. The system uses a three-rover multiagent team to perform a site-selection activity during a lunar analog mission. The work took place beginning in 2008 and culminated in a final field test on Mauna Kea in Hawaii. This demonstration of autonomous acquisition of 3D ground-penetrating radar in a space robtic application is promising not only for in-situ resource utilization, but also for the concept of multiagent teaming.