This study, conducted about 30km south of Frankfurt in the Northern Upper Rhine Graben, focuses on deepening the understanding of Radon concentrations in soil air. The selected area, where neotectonic activity was proven in an accompanying project, provides an ideal setting for investigating Radon variability, particularly its potential correlation with fault zones in unconsolidated rocks or sedimentary basins. Understanding the factors influencing Radon levels in the environment is a complex task, as they are affected by a multitude of variables. Our work aims to decipher these influences and, if possible, quantitatively analyse the contributions of each variable. By doing so, we hope to gain a clearer understanding of how different environmental factors interact to determine Radon levels. A central element of our research is the use of Random Forest models, chosen to handle our multidimensional dataset. This dataset includes a variety of parameters such as Radon measurements, nuclide content, soil grain sizes, weather data, and the distance to fault zones. Random Forest models are particularly effective for this type of complex data because they can analyse many different factors at once and uncover hidden patterns. Contrary to initial hypotheses, our findings indicate that in unconsolidated rocks and sedimentary basins, the grain size of soil is the most influential factor in determining soil air Radon levels, closely followed by soil moisture. These results challenge the previously held belief that fault zones are the primary influencing factors on Radon concentrations in these geological settings.

Radon soil air measurements and associated permeability measurements are a mandatory prerequisite for the calculation of radon potentials as an important basis for the statistical derivation of an expected radon situation in a defined area. Accordingly, in the federal state of Hesse, as almost everywhere in Germany, numerous measurements have been carried out in recent years and made available to the Federal Office for Radiation Protection (BfS) for the modelling of a radon potential map of Germany, which has since been an important (sometimes the only) basis for the definition of radon precautionary areas for all federal states in Germany. The associated benefits are undoubtedly great. From a geological perspective, however, the question arises to what extent the large lateral variability of measurable radon concentrations also exists in the vertical and, if so, whether this variability can be placed in a context with the geological development of the area under consideration. The background to this is the fact that the radon soil gas measurements usually address a depth of between 0.8 and 1 m below the ground surface, in rare cases reaching a depth of up to 2 metres. In addition to the scientific added value, such an investigation approach is also associated with an applied benefit, as building foundations are usually founded significantly deeper than 1 m below the ground surface, which means that a significant part of the building envelope in contact not only with the soil layers, but also to the geological subsurface, must be seen decoupled from the radon concentration determined near the surface, depending on the heterogeneity of the geological bedding. For this reason, we took a total of 175 samples along an 323 m deep research drilling in the northern Upper Rhine Graben and determined the radon concentration for these in the laboratory (= stationary). The results show a very high variability of the measurable radon concentrations, ranging from 16 Bq/m³ to 9086 Bq/m³ with a mean value of approx. 1527 Bq/m³. At the same time, the radon concentrations determined show a very good correlation with both the geological response of the drill core and the gamma log measurements carried out. In this presentation, we would like to show the results obtained so far and look at the possibility of regionalising the measured values as well as the next work steps.

A comprehensive multi‐method geophysical strategy is used to investigate two faults in the Northern Upper Rhine Graben. Combining industrial 3D seismic data with our own 2D P‐ and S‐wave seismic, electrical resistivity tomography (ERT) and ground‐penetrating radar (GPR), we created comprehensive subsurface images of the faults. 3D seismic data feature structure from 450 m to 4 km deep, whereas high‐resolution 2D P‐wave data complemented this for depths of 50–600 m. S‐wave seismic imaging revealed disrupted layering and syn‐sedimentary features in the range of 5–250 m depth, whereas ERT measurements further supported the identification of offset horizons and showed syn‐sedimentary activity, particularly down to 10 m depth. GPR results remained ambiguous, though they suggested potential geological features related to fault tectonics. Both faults have varying dip angles and offsets in different stratigraphic units, proving that tectonic movement occurred during sedimentation of the Neogene and Quaternary layers. In general, both faults steepen upwards, forming typically listric shapes. They both offset the base Quaternary by about 35 m. Finally, the very‐near‐surface methods show that the faults extend almost up to the Earth's surface, proving their very recent activity. This project highlights the efficiency of multi‐method geophysical surveys in neotectonic research and seismic risk assessment and emphasizes their role in detailed subsurface analysis. It also contributes to our understanding of potential gas migration along fault zones to the Earth's surface.

While 3D city models are now available for many large and medium-sized cities and are increasingly being used, the urban subsurface (= urban geology) continues to be neglected in such models in most cases. The reasons for this are both inhomogeneous and complex geological/hydrogeological information, which at the same time is not assembled in a context-specific way, as well as a lack of standards, interfaces and exchange formats. To overcome these barriers, geological and hydrogeological 2D and 3D content is currently being elaborated for several urban areas in the federal state of Hesse in close cooperation with the municipal cooperation partners using all available input data (in particular, however, boreholes, geological cross sections and groundwater level measurements), which are being assembled with a view to defined "urban geoparameters". In addition, an attempt will be made to visualize the urban underground infrastructure (man-made objects) in 3D space and thus bring it into a synopsis with the geological and hydrogeological 2D and 3D content. The synopsis, in turn, should be carried out in the respective working environments as far as possible, i.e. using the software solutions operated by the cooperation partners. To ensure this, both suitable interfaces and a suitable exchange format are required in the 3D data management systems for geological/hydrogeological models. The OGC API 3D GeoVolume and Styles interfaces and the 3D Tiles exchange format are considered to be the solution here. With this presentation, we would like to present the current state of work with a focus on the parameterisation and packaging of geological and hydrogeological 2D and 3D data for urban areas.

The health impacts of the radioactive Radon are well-documented by the World Health Organization (WHO) and numerous studies. Geogenic Radon Potential (GRP) refers to the natural production of Radon by the Earth, independent of anthropogenic influences. GRP has been a focal point of research aimed at understanding the factors influencing radon variability and its spatial distribution. However, the limited availability of systematic soil-gas radon concentration measurements, along with other constraints, often leads to coarse-resolution modeling of GRP. With the availability of adequate and quality data, regional studies can be promising in investigating these influencing factors, and modelling of GRP hazards at finer spatial scales. This study uses GRP survey data provided by the Hessian Agency for Nature Conservation, Environment and Geology (HLNUG) to develop machine learning models for predicting the spatial distribution of GRP in the state of Hessen, Germany, and to produce a high-resolution GRP hazard map. The models employed include Random Forest Regressor (RF), Support Vector Regressor (SVR), Gradient Boosting Regressor (GBR), and Multi-Layer Perceptron Regressor (MLPR). The dataset comprises 1,509 GRP sampling points for an area of about 21.000 km², and 37 potential predictors related to geology, soil characteristics, and climatic variables—key factors known to influence radon levels. Sequential Feature Selection (SFS) and a 5-fold spatial cross-validation strategy were employed to mitigate autocorrelation effects and enhance model generalization. Model performance was evaluated using multiple metrics and compared against ground-truth values and local geology. Results revealed that the RF and GBR models outperformed others, achieving R² scores of 0.69 and 0.65 on the validation dataset, respectively, while the SVR and MLPR models underperformed. Predicted GRP values ranged from 8.9 to 178.2 for RF and 1.7 to 268.4 for GBR. Geological and soil properties emerged as the dominant predictors of GRP variability in Hessen, with predicted maps highlighting a strong dependence on local geological features. High-risk areas were effectively identified by the RF model. The study also highlights the need for additional measurements in data-scarce regions and the exploration of hybrid physics-based models that integrate domain-specific knowledge into spatial predictions.

In the western Bergstr & auml;sser Odenwald, there is evidence of NNE-SSW striking brittle fault zones that divide the crystalline basement into a mosaic of faulted blocks. The fault zones have not yet been fully recognised and mapped, but are apparently tectonically active, evidenced by recent earthquake series in the region. The aim of this study is to investigate a suspected tectonic fault zone that can be traced from Bensheim to Traisa and for which there are morphological, tectonic and petrographic indications. In order to better understand the course and character of the faults, fault plane measurements are carried out in outcrops and the subsurface is explored in poorly exposed areas along two transects using geoelectrics and radon soil gas measurements. The findings from direct and indirect investigations can be consistently integrated into a superordinate fault model, which is very probably genetically related to the formation of the Upper Rhine Graben. In the Eocene, the formation of a NNE-SSW oriented extensional fault zone within the crystalline basement begins, which is still active to the present day and is now in a state of sinistral transtension.

Radon (Rn) is a naturally occurring radioactive gas that poses a significant lung cancer risk. Subsurface fault zones can act as pathways for fluid and gas migration, potentially amplifying Rn accumulation. This study investigates the impact of fault zones on Rn concentrations within a 25 km2 area in the Northern Upper Rhine Graben, Germany - a region with available detailed geophysical exploration data and active neotectonic faulting. We conducted 597 Rn soil air measurements along precisely located fault zones, integrating a comprehensive range of environmental parameters. Utilizing the advanced machine learning model eXtreme Gradient Boosting (XGBoost) in conjunction with SHapley Additive exPlanations (SHAP) values, we dissected the influence of soil types, environmental factors, and proximity to fault zones on soil air Rn concentrations at a 1-meter depth. Our results reveal that clay-rich soils and cumulative 30-day precipitation are the primary drivers of elevated Rn levels. Proximity to fault zones also significantly influences Rn concentrations, though its impact is less pronounced than the factors mentioned above. Additionally, environmental factors such as wind speed, air pressure, and temperature exhibited lesser effects on Rn levels. The negligible influence of measuring devices and operating personnel increases confidence in data integrity in extensive environmental studies. This study demonstrates the effectiveness of integrating XGBoost with SHAP values to identify and quantify key factors influencing Rn concentrations. By providing a robust framework for enhancing Rn prediction models through machine learning, our findings contribute to improved risk assessments and mitigation strategies, thereby advancing public health and environmental management.

<p>Within the framework of the project Neotectonics in the Northern Upper Rhine Graben (NeoNORG), the relationship between fault zones in a sedimentary basin and associated radon anomalies is investigated. The area of interest is located west of Darmstadt near the village Wolfskehlen. Radon levels in the Quaternary strata of the Upper Rhine Graben are generally low or moderate. However, tectonic fault zones could represent pathways of increased gas permeability and advective gas transport which would result locally in elevated soil radon concentrations. </p><p>A multi-method geophysical approach was chosen to visualise the subsurface structure. Each method has different advantages in terms of penetration depth and resolution (i.e., electrical resistivity tomography, ground penetrating radar and seismics of different wave types). The combination of these different geophysical investigation methods allows to trace the fault zones from the crystalline basement of the sedimentary basin at a depth of 2 km to several metres below the earth's surface.</p><p>To investigate the relationship between radon concentration and fault zones, soil gas measurements were carried out at the surface along several profiles. In total 800 soil gas measurements were conducted, in which 600 active short-term measurements were conducted by soil gas sampling and 200 passive long-term measurements (three-week exposure period) were conducted using exposimeters. In addition, parameters such as soil material, weather conditions and soil permeabilities were recorded.</p><p>The evaluation of the measurements indicates no direct influence of the fault zones on the measured radon levels. Instead, there are very distinct correlations with the soil substrate and weather conditions. The preliminary results suggest that the migration of radon or the accumulation of primordial radionuclides along fault zones is superimposed by stronger signals such as weather and soil material in the study area of the Northern Upper Rhine Graben.</p>

Low enthalpy ground-source heat pump systems can provide a low-cost, low-carbon, sustainable method for heating and cooling buildings; these systems can be classified as either "open loop" or "closed loop" systems. This chapter presents three case studies concerning the application of 3-D subsurface information to assess and develop shallow and deeper geothermal resources. The first case study describes the modeling used to support development of a shallow low enthalpy ground source heat pump system at Zaragosa, Spain. The second case study describes the TransGeoTherm project which promoted and supported the development of shallow geothermal resources in the Saxon-Polish trans-boundary region and made the results of geothermal modeling and mapping available to the public. The third case study describes the modeling used to assess the deeper geothermal resources in the Upper Rhine Graben in the German State of Hesse.

This chapter contains three case studies that demonstrate a variety of approaches to the incorporation of 3-D subsurface information within urban planning activities. The first case study describes an ongoing pilot study for city of Darmstadt that employs an integrated 3-D modeling approach to combine information on underground infrastructure and building foundations with subsurface geological conditions. The second case study describes the long-term collaboration between the British Geological Survey and Glasgow City Council to provide subsurface knowledge for Glasgow development and planning processes. The third case study provides an insight into the potential use of 3-D models for the urban planning required by the rapidly growing mega-cities of south-east Asia. The 3-D model was developed in three main stages: data acquisition and preparation, 3-d model construction, and dissemination of model products. Urban 3-D subsurface geological models are increasingly used to facilitate more effective use of ground investigation data and help advance understanding of subsurface conditions.

Die Stadt Darmstadt liegt am Rande des Oberrheingrabens und das Kongresszentrum „darmstadtium“ wurde direkt auf der Randstorung errichtet. Der dabei freigelegte Anschnitt der Verwerfung wurde zuganglich gemacht und zur Einrichtung einer Messstation genutzt. Hier beschreiben wir den Neuaufbau der Station ab dem Jahre 2016 mit dem jetzt verfugbaren Instrumentarium zur Uberwachung der Kriechvorgange an der Storung.

A joint project by the Department of Geology of the Estonian Land Board and the Department of Geoinformation of the Institute of Applied Geosciences at Technische Universitat Darmstadt resulted in several 3D-models of northeastern Estonia for (i) better understanding of the sedimentary bedrock, and (ii) evaluating the geopotentials therein. We implemented GOCAD and SKUA software for the first time in Estonia, and as a result, the spatial distribution of the major pre-Quaternary horizons (Devonian, Ordovician, Cambrian, Neoproterozoic and Crystalline Basement) was clarified. Two larger scale models of oil shale prospects enable the calculation of the thickness and volume of the mineral reserves.Due to the quality control of the input data during the modelling process different stakeholders like governmental authorities, research institutions and mining industry can achieve great benefits by pooling their resources, such as the identification of 135 wells with incorrect coordinates or drilling location.

To aide in land use decision-making for the protection of groundwater quality, many countries have consider to apply the aquifer vulnerability maps. A detailed intrinsic groundwater vulnerability assessment was developed by applying the standard “DRASTIC” and “GLA” methods, integrated to a Geographical Information System (GIS), to analyze a variety of hydrogeological settings, besides the land use and land cover data assessment in a small river basin localized in the Rhine-Main plains, central part of Germany. Thus, the superposition of mapped layers showed some relevant conflicts among the areas with the higher index values for groundwater vulnerability and the pre-defined areas by the governmental regional spatial planning. In an overall analysis, the major part of these high groundwater vulnerability areas were not matching the groundwater protection zones. Beyond that, a significant part of the groundwater protection zones was not intersected with the groundwater recharge zones, but matching, essentially, the areas mapped as forest and green lands. However, most of potential pollution sources related to the land use in this catchment (mining, industries, agriculture, settlements etc.) were placed along the river’s banks, but in a relative distance from the groundwater protection zones and the most vulnerable areas.

Radon measurements are currently under way along newly discovered faults in the northern Upper Rhine Graben near Groß-Gerau. Measurements of radon activity in soil air should show if the disruptions are recently active. In the process, it is difficult to compare the measurements of soil types, with different permeability, without logging the actual air flow. It is intended therefore to develop a standardised method which combines the measurement of radon with the detection of CO2 in soil air. Outcomes will be used for correlation with radon concentrations in the indoor air of buildings in the region of Darmstadt (Kuhn 2013), which is situated in the tectonically active northern Upper Rhine Graben, in order to evaluate geogenic radon in the area.

Salt sequences form an integral part of many sedimentary basins worldwide. Many of these basins have experienced igneous activity either syn- or post-deposition of the salt sequences. Despite this, little work has so far been undertaken to understand magma-salt interactions within the subsurface, and how aspects such as salt halokinesis may be influenced by igneous activity. Within this paper, we detail the first direct description of relationships and textures that are developed during intrusive igneous-salt interaction. We show that salt composition appears to play a dominant role in controlling where igneous intrusions invade laterally through salt sequences in a sedimentary basin. In particular, we illustrate that hydrous salts, such as carnallite, act as preferential horizons for lateral magma intrusion. This lithological control appears primarily related to the heating and subsequent dehydration reaction of carnallite, which causes the carnallite to behave as viscous fluidal horizons, resulting in the non-brittle emplacement of magma, and spectacular peperitic salt-magma mingling textures. We suggest that heating and transformation of carnallite and other hydrous salts into viscous fluidal horizons during igneous intrusion within a regional salt sequence may act as a possible trigger for contemporaneous halokinesis, by creating fluid-like viscous detachment layers. Over longer time scales, however, a solidified rigid boxwork of dikes and sills may create zones of increased mechanical strength that will locally inhibit further salt flow.

In cooperation with the Hessian Agency for the Environment and Geology (HLUG) a GIS and gOcad based 3D model of the Quaternary has been developed for the northern Upper Rhine Graben, which hosts the metropolitan region of Frankfurt/Rhine-Main. With 9798 quality checked wells and information from hydrocarbon exploration insights regarding the depth level of the Base Quaternary were derived, which required a modification of the up to now assumed geometry of the Quaternary sediment body. The base Quaternary is affected tectonically, leading to a differentiation of the study area into at least five homogeneity regions. Differentiation into several homogeneity regions is also supported by respective sequential consistency. Considering the tectonic inventory, the base Quaternary, especially in the southern part of the study area, is located significantly deeper than has been assumed up to now. In addition, in the western part of the study area, the base Quaternary shows stepwise offsets, which have been caused by tectonic faults. Up to now an assumed outcrop of the Quaternary in that area could not be verified. New knowledge about the geometry of the Quaternary has significant influence on current issues, particularly on groundwater and related modelling. All data and results of the ongoing project are available for the HLUG on several platforms (GeODin, ArcGIS, gOcad) as both vector and raster data and support daily decision making processes in order to address the increasing pressure related to the utilisation of natural resources - soils, groundwater, raw materials, geothermal energy, building area - and the resulting land use conflicts.