14The Geological Surveying and Investigation in 3 Dimensions (GSI3D) software tool and 15 methodology has been developed over the last 15 years. Since 2001 this has been in 16 cooperation with the British Geological Survey (BGS). To-date over a hundred BGS 17 geologists have learned to use the software that is now routinely deployed in building 18 systematic and commercial 3D geological models. The success of the GSI3D methodology 19 and software is based on its intuitive design and the fact that it utilizes exactly the same data 20 and methods, albeit in digital forms, that geologists have been using for two centuries in 21 order to make geological maps and cross-sections. The geologist constructs models based on 22 a career of observation of geological phenomena, thereby incorporating tacit knowledge into 23 the model. This knowledge capture is a key element to the GSI3D approach. In BGS GSI3D 24 is part of a much wider set of systems and work processes that together make up the 25 cyberinfrastructure of a modern geological survey. The GSI3D software is not yet designed 26 to cope with bedrock structures in which individual stratigraphic surfaces are repeated or 27 inverted, but the software is currently being extended by BGS to encompass these more 28 complex geological scenarios. A further challenge for BGS is to enable its 3D geological 29 models to become part of the semantic web using GML application schema like GeoSciML. 30The biggest benefits of widely available systematic geological models will be an enhanced 31 public understanding of the subsurface in 3D, and the teaching of geoscience students. 32 33
Abstract. We conducted a designed experiment to quantify sources of uncertainty in geologists' interpretations of a geological cross section. A group of 28 geologists participated in the experiment. Each interpreted borehole record included up to three Palaeogene bedrock units, including the target unit for the experiment: the London Clay. The set of boreholes was divided into batches from which validation boreholes had been withheld; as a result, we obtained 129 point comparisons between the interpreted elevation of the base of the London Clay and its observed elevation in a borehole not used for that particular interpretation. Analysis of the results showed good general agreement between the observed and interpreted elevations, with no evidence of systematic bias. Between-site variation of the interpretation error was spatially correlated, and the variance appeared to be stationary. The between-geologist component of variance was smaller overall, and depended on the distance to the nearest borehole. There was also evidence that the between-geologist variance depends on the degree of experience of the individual. We used the statistical model of interpretation error to compute confidence intervals for any one interpretation of the base of the London Clay on the cross section, and to provide uncertainty measures for decision support in a hypothetical routeplanning process. The statistical model could also be used to quantify error propagation in a full 3-D geological model produced from interpreted cross sections.
The development of an attributed 3D model of the Quaternary deposits across 75 km that modelling of this type should be used by site developers and remediators to design more targeted and cost-effective site investigations and risk assessments.
Field and numerical investigations at Happisburgh, East coast of England, UK, sought to characterize beach thickness and determine geologic framework controls on coastal change. After a major failure of coastal protection infrastructure, removal of about 1 km of coastal defence along the otherwise protected cliffed coastline of Happisburgh triggered a period of rapid erosion over 20 years of ca. 140 m. Previous sensitivity studies suggest that beach thickness plays a major role in coastal recession. These studies were limited, however, by a lack of beach volume data. In this study, we have integrated the insights gained from our understanding of the Quaternary geology of the area, a novel non-intrusive passive seismic survey method, and a 3D novel representation of the subsurface source and transportable material into a coastal modelling environment to explore the role of beach thickness on the back wearing and downwearing of the cliffs and consolidated platform, respectively. Results show that beach thickness is non-homogeneous along the study site: we estimate that the contribution to near-shore sediment budget via platform downwearing is of a similar order of magnitude as sediment lost from the beach and therefore non-negligible. We have provided a range of evidence to support the idea that the Happisburgh beach is a relatively thin layer perched on a sediment rich platform of sand and gravel. This conceptualization differs from previous publications, which assume that the platform was mostly till and fine material. This has direct implication on regional sediment management along this coastline. The present study contributes to our understanding of a poorly known aspect of coastal sediment budgeting and outlines a quantitative approach that allows for simple integration of geological understanding for coastline evolution assessments worldwide.
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