A regional shear-wave velocity (V S) model has been developed for the Groningen gas field in the Netherlands as the basis for seismic microzonation of an area of more than 1000 km 2. The V S model, extending to a depth of almost 1 km, is an essential input to the modelling of hazard and risk due to induced earthquakes in the region. The detailed V S profiles are constructed from a novel combination of three data sets covering different, partially overlapping depth ranges. The uppermost 50 m of the V S profiles are obtained from a high-resolution geological model with representative V S values assigned to the sediments. Field measurements of V S were used to derive representative V S values for the different types of sediments. The profiles from 50 to 120 m are obtained from inversion of surface waves recorded (as noise) during deep seismic reflection profiling of the gas reservoir. The deepest part of the profiles is obtained from sonic logging and V P-V S relationships based on measurements in deep boreholes. Criteria were established for the splicing of the three portions to generate continuous models over the entire depth range for use in site response calculations, for which an elastic half-space is assumed to exist below a Electronic supplementary material The online version of this article (

The Geological Survey of the Netherlands aims at building a 3D geological 'GeoTOP' model of the upper 30 m of the subsurface of the Netherlands in order to provide a sound basis for answering subsurface related questions on, amongst others, groundwater extraction and management, land subsidence studies, aggregate resources and infrastructural issues. The model provides a uniformly constructed framework for subsurface information and serves as an easily accessible data source for any subsurface activities in the Dutch delta. Earlier large-scale 3D voxel models of the Netherlands were tailor made to specific applications, i.e. aggregate resources (Van der Meulen et al., 2005) and clay resources (Van der Meulen et al., 2007).The GeoTOP model is a fully three-dimensional, multi-purpose subsurface model of the onshore part of the Netherlands. In contrast to other nation-wide subsurface models, the Digital Geological Model (DGM; www.dinoloket.nl) and the REgional Geohydrological Information System (REGIS-II; Vernes and Van Doorn, 2005;Vernes et al., 2010; www.dinoloket.nl)

ScopePursuant to a new law that will become effective in 2015, DINO, the national Dutch subsurface database operated by the Geological Survey of the Netherlands, is to become an official government register (a 'key register' / basisregistratie). In facing the responsibilities associated with this new status, the Survey is reconsidering and redesigning its operation and in that process a new, or at least sharper picture is emerging of geological surveying in the future.These developments set the final stages of a process of modernisation that geological survey organisations all over the world are currently entangled in (Allen, 2003;Jackson, 2010). Most surveys are replacing paper archives that were built in the AbstractOver the last ten to twenty years, geological surveys all over the world have been entangled in a process of digitisation. Their paper archives, built over many decades, have largely been replaced by electronic databases. The systematic production of geological map sheets is being replaced by 3D subsurface modelling, the results of which are distributed electronically. In the Netherlands, this transition is both being accelerated and concluded by a new law that will govern management and utilisation of subsurface information. Under this law, the Geological Survey of the Netherlands has been commissioned to build a key register for the subsurface: a single national database for subsurface data and information, which Dutch government bodies are obliged to use when making policies or decisions that pertain to, or can be affected by the subsurface. This requires the Survey to rethink and redesign a substantial part of its operation: from data acquisition and interpretation to delivery. It has also helped shape our view on geological surveying in the future.The key register, which is expected to start becoming operational in 2015, will contain vast quantities of subsurface data, as well as their interpretation into 3D models. The obligatory consultation of the register will raise user expectations of the reliability of all information it contains, and requires a strong focus on confidence issues. Building the necessary systems and meeting quality requirements is our biggest challenge in the upcoming years. The next step change will be towards building 4D models, which represent not only geological conditions in space, but also processes in time such as subsidence, anthropogenic effects, and those associated with global change.Keywords: Netherlands, applied geoscience, hydrogeology, geological surveying, mapping, geomodelling, geodatabase Netherlands Journal of Geosciences -Geologie en Mijnbouw | 92 -4 | 217-241 | 2013 217 course of many decades by electronic databases; many surveys started producing electronically distributed 3D subsurface models in addition to or instead of 2D geological maps that were their primary output since their establishment. For a variety of reasons explained below, the Dutch survey is among the early adapters in both respects.In this overview paper we present the Geological S...

We present an interpolation model that describes Holocene groundwater level rise and the creation of accommodation space in 3D in the Rhine-Meuse delta -the Netherlands. The model area (ca. 12 400 km 2 ) covers two palaeovalleys of Late Pleistocene age (each 30 km wide) and the overlying Holocene deposits of the Rhine-Meuse delta, the Holland coastal plain, and the Zuiderzee former lagoon. Water table rise is modelled from 10 800 to 1000 cal. BP, making use of age-depth relations based on 384 basal peat index points, and producing output in the form of stacked palaeo groundwater surfaces, groundwater age-depth curves, and voxel sets. These products allow to resolve (i) regional change and variations of inland water table slopes, (ii) spatial differences in the timing and pacing of transgression, and (iii) analysis of interplay of coastal, fluvial and subsidence controls on the provision of accommodation space. The interpolation model is a multi-parameter trend function, to which a 3D-kriging procedure of the residuals is added. This split design deploys a generic approach for modelling provision of accommodation space in deltas and coastal lowlands, aiming to work both in areas of intermediate data availability and in the most data-rich environments. Major provision of accommodation space occurred from 8500 cal BP onwards, but a different evolution occurred in each of the two palaeovalleys. In the northern valley, creation of accommodation space began to stall at 7500 cal BP, while in the southern valley provision of new accommodation space in considerable quantities continued longer. The latter is due to the floodplain gradient that was maintained by the Rhine, which distinguishes the fluvial deltaic environment from the rest of the back-barrier coastal plain. The interpolation results allow advanced mapping and investigation of apparent spatial differences in Holocene aggradation in larger coastal sedimentary systems. Furthermore, they provide a means to generate first-order age information with centennial precision for 3D geological subsurface models of Holocene deltas and valley fills. As such, the interpolation is of use in studies into past and present land subsidence and into low land sedimentation.

Link to this article: http://journals.cambridge.org/abstract_S0016774614000468How to cite this article: D. Maljers, J. Staeu, M.J. van der Meulen and R.M. Dambrink (2015). Advances in constructing regional geological voxel models, illustrated by their application in aggregate resource assessments. AbstractAggregate resource assessments, derived from three subsequent generations of voxel models, were compared in a qualitative way to illustrate and discuss modelling progress. We compared the models in terms of both methodology and usability. All three models were produced by the Geological Survey of the Netherlands. Aggregate is granular mineral material used in building and construction, and in this case consists of sand and gravel.On each occasion ever-increasing computer power allowed us to model at a higher resolution and use more geological information to constrain interpolations. The two oldest models, built in 2005 and 2007, were created specifically for aggregate resource assessments, the first as proof of concept, the second for an online resource information system. The third model was derived from the ongoing multipurpose systematic 3D modelling programme GeoTOP. We used a study area of 40 × 40 km located in the central Netherlands, which encompasses a section of the Rhine-Meuse delta and adjacent glacial terrains to the north. Aggregate resource assessments rely on the extent to which the occurrence and grain size of sand and gravel are resolved, and on proper representation of clay and peat layers (overburden and intercalations) that affect exploitability. Average model properties (e.g. total aggregate content) are about the same in all three models, except for a difference resulting from converting older lithological classifications to the current one. This difference illustrates that data selection and preparation are paramount, especially when dealing with quality issues. Generally speaking the results of the aggregate resource assessments are consistent and satisfactory for all three models, provided that they are judged at the appropriate scale. However, the assessments based on GeoTOP best approach the desired scale of use for the aggregates industry;in that sense progress was significant and each model was a better fit for the purpose.