Seismic Reflection and Gravity Constraints on the Bedrock Configuration in the Greater East Missoula Area

The greater East Missoula, MT area is the site of numerous studies to track possible groundwater contamination from the EPA Superfund Site at the Milltown Dam. The accuracy of these groundwater models depends on many factors, one of which is the accuracy to which the bedrock topography is mapped. Currently, a map based heavily on a gravity survey provides the most detailed map of the bedrock. The accuracy of this map may be improved through the use of seismic reflection techniques, better estimates of the density contrast used in the gravity modeling, and by extending the gravity survey to include more data and a broader area. The seismic reflection technique used to supplement the gravity data is the optimum offset technique. This method simplifies field collection of the data and processing of the data. The final result of this method is a seismic section showing the depth to different reflectors in the subsurface, one of which is the bedrock. In order to improve the estimate of the density contrast used in the gravity modeling, the homogeneity of the valley fill was tested. This was done by comparing the results from two different modeling programs, one of which let the density contrast vary, to see if there was an improvement in the final result. The gravity survey was also extended to incorporate a larger area and more data. The results show that seismic reflection can be used to improve the depth estimate in the valley where the depth is shallow and that the density contrast is most likely homogeneous. The extended gravity survey provided more data to work with and the final result is a map of the bedrock topography for the greater East Missoula Area that incorporates all currently known data and provides a sufficiently accurate estimate of the depth to be used in groundwater models

Recent intraplate earthquakes in Northwest Germany : glacial isostatic adjustment and/or a consequence of hydrocarbon production?

[no abstract

Visual Techniques for Geological Fieldwork Using Mobile Devices

Visual techniques in general and 3D visualisation in particular have seen considerable adoption within the last 30 years in the geosciences and geology. Techniques such as volume visualisation, for analysing subsurface processes, and photo-coloured LiDAR point-based rendering, to digitally explore rock exposures at the earth’s surface, were applied within geology as one of the first adopting branches of science. A large amount of digital, geological surface- and volume data is nowadays available to desktop-based workflows for geological applications such as hydrocarbon reservoir exploration, groundwater modelling, CO2 sequestration and, in the future, geothermal energy planning. On the other hand, the analysis and data collection during fieldwork has yet to embrace this ”digital revolution”: sedimentary logs, geological maps and stratigraphic sketches are still captured in each geologist’s individual fieldbook, and physical rocks samples are still transported to the lab for subsequent analysis. Is this still necessary, or are there extended digital means of data collection and exploration in the field ? Are modern digital interpretation techniques accurate and intuitive enough to relevantly support fieldwork in geology and other geoscience disciplines ? This dissertation aims to address these questions and, by doing so, close the technological gap between geological fieldwork and office workflows in geology. The emergence of mobile devices and their vast array of physical sensors, combined with touch-based user interfaces, high-resolution screens and digital cameras provide a possible digital platform that can be used by field geologists. Their ubiquitous availability increases the chances to adopt digital workflows in the field without additional, expensive equipment. The use of 3D data on mobile devices in the field is furthered by the availability of 3D digital outcrop models and the increasing ease of their acquisition. This dissertation assesses the prospects of adopting 3D visual techniques and mobile devices within field geology. The research of this dissertation uses previously acquired and processed digital outcrop models in the form of textured surfaces from optical remote sensing and photogrammetry. The scientific papers in this thesis present visual techniques and algorithms to map outcrop photographs in the field directly onto the surface models. Automatic mapping allows the projection of photo interpretations of stratigraphy and sedimentary facies on the 3D textured surface while providing the domain expert with simple-touse, intuitive tools for the photo interpretation itself. The developed visual approach, combining insight from all across the computer sciences dealing with visual information, merits into the mobile device Geological Registration and Interpretation Toolset (GRIT) app, which is assessed on an outcrop analogue study of the Saltwick Formation exposed at Whitby, North Yorkshire, UK. Although being applicable to a diversity of study scenarios within petroleum geology and the geosciences, the particular target application of the visual techniques is to easily provide field-based outcrop interpretations for subsequent construction of training images for multiple point statistics reservoir modelling, as envisaged within the VOM2MPS project. Despite the success and applicability of the visual approach, numerous drawbacks and probable future extensions are discussed in the thesis based on the conducted studies. Apart from elaborating on more obvious limitations originating from the use of mobile devices and their limited computing capabilities and sensor accuracies, a major contribution of this thesis is the careful analysis of conceptual drawbacks of established procedures in modelling, representing, constructing and disseminating the available surface geometry. A more mathematically-accurate geometric description of the underlying algebraic surfaces yields improvements and future applications unaddressed within the literature of geology and the computational geosciences to this date. Also, future extensions to the visual techniques proposed in this thesis allow for expanded analysis, 3D exploration and improved geological subsurface modelling in general.publishedVersio

On the physical interaction between ocean waves and coastal cliffs

Wave impacts have long been posited as the primary forcing mechanism of coastal cliff recession. Recent developments in the study of hydrodynamics at coastal structures such as seawalls and breakwaters have shown that wave pressures are stochastic in nature and have a broad range of first- and second-order controls. This understanding has yet to be translated to coastal cliffs, where it is still largely assumed that wave impact characteristics can be predicted by simple deterministic formulae. Hydraulic components in coastal models are limited by the lack of in-situ measurements of waves at the cliff toe due to the difficulties in deploying instrumentation in such energetic and inaccessible environments. To address this, I have approached the problem threefold. Monthly high-resolution terrestrial laser scanning (TLS) was undertaken over a year at multiple sites at Staithes, North Yorkshire, to evaluate the recession rate and detachment characteristics of the lower cliff section. Concurrently, wave gauges were deployed at the cliff toe of each site to monitor wave conditions. A novel method of measuring wave impacts was undertaken at one of the sites for nine low-to-low tidal cycles. New and established methods for processing this data were used. Analysis of the erosion dataset revealed distinct temporal patterns of erosion, with accelerated erosion rates during winter. Vertical variations in detachment volumes below 0.1 m3 related to the tidal elevation were also observed, suggesting a key marine influence. Detachment frequency and volume were found to be influenced by lithology type and joint density. Wave conditions over the study period were found to be depth-limited, yet some waves at the toe were found to be larger than those offshore due to shoaling. Wave breaking conditions were strongly influenced by platform morphology and tidal stage. Up to 9% of all waves were breaking on impact. Measurements of wave impacts revealed approximately 14% of wave exhibited high-magnitude impulsive pressures generated by breaking and broken waves. These were analysed probabilistically and found to be controlled primarily by the ratio between wave height and water depth. These data were used to develop a conceptual model of forcing at the cliff toe, including an evaluation of the ability of waves to remove material via enhanced pressure inside discontinuities and fragmentation of weathered material. These results have broad implications concerning the process geomorphology of rock coasts and the evaluation of wave forcing in coastal models

The application of historical data and computational methods for investigating causes of long-term morphological change in estuaries : a case study of the Mersey Estuary, UK

Long-term morphological change in estuaries, of the order of 100 years, has developed into an area of significant research interest as a result of increased regulation and management of estuarine environments. The long-term behaviour of estuary morphology results from the net effects of perturbations induced by tidal, seasonal and episodic events, averaged over a longer period. Theoretically a dynamic equilibrium may exist between deposition and erosion when considered over a time period that is sufficiently long to encompass the cyclic variability that exists within an estuarine system. However the assemblage of physical processes required for a stable state to exist, and the causes of deviation from a stable state, are not well understood. The interaction of physical processes of tidal and wave action, and the influence of sea level rise and anthropogenic activity, with estuarine ecology and geology are largely responsible for the evolving state of an estuary. Although the physical processes of tidal movement and wave action are well known and documented, the interaction of these processes with factors controlling estuarine evolution over long time periods is less well understood. This thesis evaluates approaches to analysing historical data and applying computational methods to examine the interaction between factors forcing long-term estuary morphology. Historical data is of considerable value to analysis of long-term morphological change in estuaries, and forms a pre-requisite for developing understanding of the nature and causes of the long-term evolution of estuary morphology. However few data sets exist which cover a period of sufficient duration with sufficient detail to identify the processes forcing morphological change, so recourse to computational methods is required for the purpose of developing understanding of estuary behaviour. Several techniques are employed, including analysis of bathymetric data, calculation of analytical parameters and computational hydrodynamic simulations, to develop a case study of processes causing morphological change in the Mersey estuary over the last century. A major requirement for the approach adopted in this thesis is the identification and reduction of uncertainty. Areas of uncertainty are identified, and the results arising from various computational techniques employing different assumptions are examined within a framework enabling evaluation of the uncertainty arising from analysis and assumptions upon which it is reliant. Volumetric analysis demonstrates that morphological change is dominated by a trend of significant accretion between 1906-1977, with tidal volume reducing by approximately 10% (70Mm3). Previous research has identified the construction of training walls, between 1906-36 to stabilise the position of the low water channel in Liverpool Bay outside the estuary, as a probable cause of perturbation. Changes to tidal flow and related sediment transport patterns outside the estuary resulting from training wall construction are examined with regard to the stability of the estuary system. The results from computational hydrodynamic models representing the years 1906, 1936 and 1977 quantifying potential changes in sediment transport pathways from outside the estuary indicate a significant increase in potential sediment supply to the mouth of the estuary during the period of peak accretion. However, these changes cannot be solely attributed to construction of the training walls, but result from the combined effect of training wall construction and dredging activity in the sea approach channels. Furthermore, it is not simply changes in tidal flow characteristics that cause sedimentation but also the existence of salinity induced gravitational circulation within the estuary and the wider Liverpool Bay system that acts as an important mechanism for importing sediment into the estuary. Evidence for evolution towards a stable estuary state is provided by derivation of a sediment budget demonstrating a negligible net flux of sediment into the estuary between 1977-1997. The establishment of a steady state is attributed to a reduction in the calculated transport of sediment, from west to east, across Liverpool Bay reducing the supply of sediment to the estuary mouth

Reconstruction of the Past and Forecast of the Future European and British Ice Sheets and Associated Sea–Level Change

The aim of this project is to improve our understanding of the past European and British ice sheets as a basis for forecasting their future. The behaviour of these ice sheets is investigated by simulating them using a numerical model and comparing model results with geological data including relative sea–level change data. In order to achieve this aim, a coupled ice sheet/lithosphere model is developed. Ice sheets form an integral part of the Earth system. They affect the planet’s albedo, atmospheric and oceanic circulation patterns, topography, and global and local sea–level change. In order to understand how these systems work, it is necessary to understand how ice sheets interact with other parts of the climate system. This project does this by simulating ice behaviour as part of the climate system and evaluating model behaviour in relation to evidence of past ice sheets. Ice sheet simulations can be treated with more confidence if they can be evaluated against independent data. A methodology is therefore developed that compares relative sea–level records with simulations of past sea–level which result from modelling past ice sheets with a dynamic, high–resolution thermo– mechanical ice sheet model coupled to an isostatic adjustment model. The Earth’s response to changing surface loads is simulated using both a regional, flat Earth approximation and a global, spherical self–gravitating Earth model. The coupled model is tested by initially simulating the past Fennoscandian ice sheet because of the simpler topographic framework and the quality of geological evidence of past fluctuations against which to evaluate model behaviour. The model is driven by a climatic forcing function determined so that the simulated ice sheet resembles the past Fennoscandian ice sheet as reconstructed from geomorphological evidence. The Fennoscandian climate driver is then transferred to the British Isles to simulate the past British ice sheet. Finally, a non–linear regression technique is used to construct future ice sheet drivers from future sea– level change scenarios to forecast sea–level change around the British Isles during the next glacial cycle. The data used for the inversion procedure is limited to southern Scandinavia. Outside this area, the simulation compares poorly with reconstructions based on geological observations. However, model fit within this region is good and the simulation is also in good agreement with features not used during the inversion process. This approach illustrates the benefit of using a model coupling realistic ice physics to a realistic Earth model to help constrain simultaneously unknowns of Earth rheology and ice thickness. Ultimately, relative sea–level data together with other strands of data, such as geomorphological evidence, and a coupled ice sheet/isostatic rebound model can be used to help infer past climates

National synchrotron light source. Activity report, October 1, 1995--September 30, 1996

The hard work done by the synchrotron radiation community, in collaboration with all those using large-scale central facilities during 1995, paid off in FY 1996 through the DOE`s Presidential Scientific Facilities Initiative. In comparison with the other DOE synchrotron radiation facilities, the National Synchrotron Light Source benefited least in operating budgets because it was unable to increase running time beyond 100%-nevertheless, the number of station hours was maintained. The major thrust at Brookhaven came from a 15% increase in budget which allowed the recruitment of seven staff in the beamlines support group and permitted a step increment in the funding of the extremely long list of upgrades; both to the sources and to the beamlines. During the December 1995 shutdown, the VUV Ring quadrant around U10-U12 was totally reconstructed. New front ends, enabling apertures up to 90 mrad on U10 and U12, were installed. During the year new PRTs were in formation for the infrared beamlines, encouraged by the investment the lab was able to commit from the initiative funds and by awards from the Scientific Facilities Initiative. A new PRT, specifically for small and wide angle x-ray scattering from polymers, will start work on X27C in FY 1997 and existing PRTs on X26C and X9B working on macromolecular crystallography will be joined by new members. Plans to replace aging radio frequency cavities by an improved design, originally a painfully slow six or eight year project, were brought forward so that the first pair of cavities (half of the project for the X-Ray Ring) will now be installed in FY 1997. Current upgrades to 350 mA initially and to 438 mA later in the X-Ray Ring were set aside due to lack of funds for the necessary thermally robust beryllium windows. The Scientific Facilities Initiative allowed purchase of all 34 windows in FY 1996 so that the power upgrade will be achieved in FY 1997