Katherine Royse

Combining numerical and cognitive 3D modelling approaches in order to determine the structure of the Chalk in the London Basin

In order to determine the structure of the Chalk in the London Basin, a combined cognitive and numerical approach to model construction was developed. A major difficultly in elucidating the structure of the Chalk in the London Basin is that the Chalk is largely unexposed. The project had to rely on subsurface data such as boreholes and site investigation reports. Although a high density of data was available problems with the distribution of data and its quality meant that, an approach based on a numerical interpolation between data points could not be used in this case. Therefore a methodology was developed that enabled the modeller to pick out areas of possible faulting and to achieve a geologically reasonable solution even in areas where the data was sparse or uncertain. By using this combined approach, the resultant 3D model for the London Basin was more consistent with current geological observations and understanding. In essence, the methodology proposed here decreased the disparity between the digital geological model and current geological knowledge. Furthermore, the analysis and interpretation of this model resulted in an improved understanding of how the London Basin evolved during the Cretaceous period.

The use of 3D geological models in the development of the conceptual groundwater model

The conceptual groundwater model is heavily dependent on the geological framework which is used to defi ne the aquifer being studied. In the past, two-dimensional datasets such as geological maps and cross-sections were used in coordination with site-specifi c point data to build a conceptual understanding at the site or catchment scale. This is then simplified and it is this simplifi ed version which is used to build the framework for the numerical groundwater fl ow model. Due to the way the geological framework model and the conceptual groundwater model were generated they could not be viewed together; this inevitably led to a signifi cant loss of information and understanding. With the current rapid developments in 3D modelling software and the increasing availability of digital geological data it is now possible to produce detailed 3D geological models of complex aquifer sequences. In this paper we will use two case studies (Chalk aquifer of the London Basin and the Jurassic limestone aquifer of the Cotswolds) to demonstrate that by developing a detailed 3D geological model signifi cant benefi ts are gained in the understanding and development of the conceptual groundwater model.

Anomalous buried hollows in London: development of a hazard susceptibility map

Engineering works carried out in central London over many decades have revealed a number of buried hollows that exhibit curious characteristics. Some extend deep into the bedrock geology and are in-filled with disturbed superficial deposits and reworked bedrock. Others are contained within the superficial deposits. They can be up to 500 m wide and more than 60 m in depth. As the infill material often has different behavioural characteristics from the surrounding deposits failure to identify them during an initial site investigation can prove costly. This paper considers their common characteristics and describes the method used to develop a buried hollow hazard susceptibility map. This map provides planners with a broader awareness of the potential location of difficult ground conditions associated with them, thereby reducing the potential for unforeseen ground conditions through effective site investigation design. The paper continues with a discussion of some of the likely processes associated with their formation, which are attributed to cryogenic processes, and concludes with potential future research directions.

Chalk: its stratigraphy, structure and engineering geology in east London and the Thames Gateway

Abstract The geology of the Chalk beneath east London and the Thames Gateway is reviewed and key features affecting engineering geology are summarized. In particular, the variable stratigraphy preserved beneath the sub-Palaeogene erosion surface, the evidence for syndepositional tectonics in the Chalk, and the recognition of tectonic fractures and strata-bound fracture systems are emphasized. The contrasting physical properties of chalk and flint are discussed and the depth of weathering in the subcrop and outcrop are compared and contrasted. The information gained from separate ground investigations is combined to suggest that there are regions in east London where better quality chalk and less permeable ground are present between regions of poorer quality chalk with higher permeability, closely related to zones of faulting.

Geological 3D modelling : scientific discovery and enhanced understanding of the subsurface, with examples from the UK

In recent years, with the improvement of computer processing power and the development of sophisticated visualisation software, the traditional static views of geological maps, cross-sections and other analogue representations have been replaced by digital, three-dimensional (3D) models. Building these 3D models involves the assembly of many previously isolated and disparate datasets into a single 3D spatial framework for visualisation and analysis. This enables the construction of the best possible geological 3D model using all available information. This paper gives examples of how geoscientific understanding has benefited from the construction of 3D models by the British Geological Survey using several examples to illustrate how structural, stratigraphical and sedimentological discovery can result from the construction of 3D models.

The modelling and visualization of digital geoscientific data as a communication aid to land-use planning in the urban environment: an example from the Thames Gateway

Abstract The Thames Gateway Development Zone is the biggest urban development project in the UK for over 50 years. Developers and planners need to understand the implications of such large-scale urbanization on the environment. Requirements for sustainable growth within the Thames Gateway region mean that developers are being required to demonstrate that proposals are based on sound scientific information. This has resulted in a growing demand for geo-environmental information to be provided in more accessible, relevant and understandable forms. Advances in the use of geographic information systems (GIS) and 3D modelling software mean that there is now far greater opportunity to develop geo-environmental information products for urban development. New and innovative ways of visualizing and communicating geoscience information have been developed. Using this new technology it is possible to predict not only the types of rocks beneath a site, but also the engineering properties (such as rock strength, shrink–swell characteristics or compressibility), hydrogeological properties (such as permeability, porosity and thickness of the unsaturated zone) and geohazard potential. Geoscientific information can then be imported into standard GIS packages and queried along with other complementary ground investigation data, resulting in the creation of a powerful tool to assist in strategic planning and sustainable development.

The development of a GIS methodology to assess the potential for water resource contamination due to new development in the 2012 Olympic Park site, London

The Initial Screening Tool (IST) has been developed to enable Planners to assess the potential risk to ground and surface water due to remobilisation of contaminants by new developments. The IST is a custom built GIS application that improves upon previous screening tools developed by the British Geological Survey (BGS) through the inclusion of 3-D geological data and an enhanced scoring methodology. The key new feature of the IST is the ability to track individual pollutant linkages, from a source of contamination, along multiple possible Pathways to potentially susceptible Receptors. A rule based approach allows the methodology to be easily updated, and as a result the IST has a role in scenario planning. The application provides output in the form of an automatically generated report, in which details of the potential pollutant linkages identified are presented. The initial research area selected was the Olympic Park site, London.

Country-rock contamination of marginal mafic granulites bordering the Nain Plutonic Suite: implications for mobilization of Sr during high-grade contact metamorphism

The marginal mafic granulites that locally border the Nain Plutonic Suite (NPS) have a range of initial Ndisotope ratios that overlap with that of the NPS anorthosites and associated Nain dykes. The similarity in Nd-isotope data suggests that gneissic Archaean country rocks have contaminated all the anorthosites, marginal mafic granulites, and dykes. Sr-isotope data for the mafic granulites and dykes support a country rock contamination scenario but preclude wholesale assimilation of rocks such as the host Archaean tonalite gneisses as the sole contaminant. Initial εSr values of +10 to +403 and +0.9 to +242 for the mafic granulites and dykes, respectively, are significantly higher than values for NPS country rocks examined thus far. The elevated initial εSr values are therefore interpreted to result from the introduction of radiogenic Sr into the granulites and dykes via Sr-rich fluids, generated by the breakdown of Rbrich mineral phases such as biotite in the country rocks during NPS. Résumé : Les granulites mafiques marginales, qui bordent localement la Suite plutonique de Nain, fournissent des variations de rapports isotopiques initiaux de Nd qui chevauchent les valeurs des anorthosites de la Suite plutonique de Nain, et des dykes associés dans la Province de Nain. Cette similitude des données isotopiques de Nd suggère que des roches gneissiques encaissantes archéennes ont contaminé toutes les anorthosites et les granulites mafiques marginales, et les dykes également. Les données isotopiques de Sr obtenues pour les granulites mafiques et les dykes plaident en faveur d’un scénario de contamination des roches encaissantes, mais elles excluent que l’unique mécanisme de contamination serait l’assimilation en gros des roches hôtes, par exemple les gneiss tonalitiques d’âge archéen. Les valeurs εSr de +10 à +403 et de +0,9 à +242 que procurent les granulites mafiques et les dykes, respectivement, sont significativement plus élevées que les valeurs obtenues pour les roches encaissantes de la Suite plutonique de Nain qui ont été examinées jusqu’à présent. Les fortes valeurs des εSr initiaux sont donc interprétées comme le résultat de l’ajout de Sr radiogénique dans les granulites et les dykes par les venues de fluides riches en Sr, suite à la destruction des minéraux riches en Rb, comme la biotite des roches encaissantes, durant la mise en place de la Suite plutonique de

The potential for the use of model fusion techniques in building and developing catastrophe models

Abstract Global economic losses related to natural hazards are large and increasing, peaking at US

Superficial Hollows and Rockhead Anomalies in the London Basin, UK: Origins, Distribution and Risk Implications for Subsurface Infrastructure and Water Resources

380 billion in 2011 driven by earthquakes in Japan and New Zealand and flooding in Thailand. Catastrophe models are stochastic event-set based computer models, first created 25 years ago, that are now vital to risk assessment within the insurance and reinsurance industry. They estimate likely losses from extreme events, whether natural or man-made. Most catastrophe models limit the level of user interaction, stereotyped as ‘black boxes’. In this paper we investigate how model fusion techniques could be used to develop ‘plug and play’ catastrophe models and discuss the impact of open access modelling on the insurance industry and other stakeholders (e.g. local government).