Deformation of the Earth’s crust is fundamentally governed by subsurface stress and pore fluid pressure, which together define effective stress as the difference between total stress and pore pressure. Effective stress controls a wide range of processes, such as fluid migration, sediment compaction, subsidence, fault reactivation and the earthquake cycle. It is also a key parameter for the design of subsurface engineering such as drilling operations, fluid and heat production as well as storage of CO2, radioactive waste, hydrogen and energy. For the safe exploration and operation of georeservoirs and for the development of mitigation strategies of induced hazard such as borehole failure, leakage due to fault reactivation, or induced seismicity a reliable quantification of the effective stress is essential.Over the past four decades, subsurface horizontal stress orientations and, more recently, stress magnitudes have been systematically compiled and analysed using dedicated quality-ranking schemes. The data are publicly available through the World Stress Map (WSM) database. In contrast, pore pressure data remain fragmented and inconsistently documented. Where available, pore pressure information is typically dispersed across national, regional, commercial or private databases, as well as scientific publications and technical reports. Publicly accessible pore pressure databases are rare and generally lack standardised formats or the application of a common quality assessment. Furthermore, although pore pressure measurements have been collected since the early development of deep drilling primarily by the petroleum industry, most datasets have not been published due to confidentiality concerns. Consequently, pore pressure information is often limited to isolated case studies or regional analyses that neither provide digital data nor precise spatial referencing.As a result, a global database with quality-ranked pore pressure data complementary to the WSM does not yet exist. This absence represents a major limitation for both fundamental geoscience research and practical application in reservoir management required for a sustainable energy future. To address this gap, this contribution aims to initiate the development of a global database using a quality-ranking scheme for direct pore pressure measurements and indirect pore pressure indicators. The proposed open-access resource referred to as the World Pressure Map is intended to combine data from different methods to make them comparable and to ensure long-term data availability.

The present-day crustal stress state is a key parameter for the assessment of a potential siting region for a deep geological repository (DGR) of radioactive waste. It is also crucial for the DGR design and the evaluation of its long-term safety. Therefore, a three-dimensional description of the stress state, including both orientations and magnitudes, is required not only for the repository host rock but also for the underlying and overlying formations that act as additional geological barriers.For the site selection process in Germany, we present results from an updated large-scale 3D geomechanical-numerical model developed within the SpannEnD project. For the model calibration, we employ a new compilation of data records of the orientation of the maximum horizontal stress SHmax as well as stress magnitude data of SHmax and the minimum horizontal stress Shmin. The model geometry is based on a new geological model of Germany and comprises 50 individually parameterized units. We assume linear elasticity and assume that the stress state is a superposition of gravitational volume forces and surface forces related to plate tectonics. The resulting partial differential equations describing the force equilibrium are solved numerically using the finite element method. The model consists of approximately 107 hexahedral finite elements allowing a vertical resolution of ~50 m within the uppermost 5 km of the model.To avoid overrepresentation of data clusters, we compare our modeled stress orientations with estimates of the mean SHmax orientation on a regular grid using the data records from the new WSM release 2025. The model results show good agreement with the mean SHmax orientation with a mean of the absolute differences of ~10°. Furthermore, our model results indicate an improved prediction of Shmin in comparison to previous models with a mean of the absolute stress differences with regard to the calibration data records of 2.5 MPa. The modeled SHmax magnitudes exhibit larger deviations from the calibration data with a mean of the absolute differences of 7.5 MPa. These discrepancies are probably attributed to uncertainties associated with the common derivation of SHmax magnitudes from the Shmin data. To further improve the reliability of the model results, additional reliable data records of the SHmax magnitude are required as they currently represent the largest source of uncertainty in the model results.

The Enguri Dam in Georgia, supplying about one-third of the country's energy, is built in a karst region. Understanding subsurface flow, controlled by bedding, fractures, and faults, is crucial to prevent failures. We improved knowledge of their spatial distribution by combining literature data, field measurements, and analysis of the DAMAST-KIT-Spartak borehole. Two fracture sets are of utmost importance: one parallel to bedding (dipping ESE) observed throughout the borehole, and another dipping WSW, present only in the upper 113 m, likely caused by valley incision and unloading. Piezometer and tracer test data reveal that these fractures also control hydraulic flow paths. Shallow flow occurs along fractures parallel to valley slopes, which remain open due to near-surface stress. At greater depth, flow is governed by bedding-parallel faults dipping into the flanks due to the anticlinal structure. Piezometers upstream of the grout curtain show stronger connectivity on the left valley flank; this is reduced downstream, indicating the curtain‘s effectiveness in lowering hydraulic pressure. The Branch Fault beneath the right abutment shows a low hydraulic response and is therefore interpreted not to serve as a major flow path.

Understanding perturbations caused by underground fluid injection and extraction is essential for steady long-lasting operations of subsurface energy systems (e.g. geothermal systems). The systems are often too complex to obtain precise analytical solutions and computationally expensive to have fine numerical results. Simplified settings give the benefit of understanding the role of driving geological parameters as well as examining the limits of each approach. In this study, we focus on the influence of permeability on pore pressure and present analytical and numerical solutions of spatial and temporal evolutions of pore pressure in an elastic homogeneous porous media with isotropic and anisotropic permeabilities. We use COMSOL Multiphysics to build a 3D finite element model with injection/production wells and investigate where the numerical solutions of the spatially limited volume coincide and diverge from corresponding analytical solutions of pore pressure in infinite media.

Joint petrophysical, geochemical, and petrographic studies on Barremian carbonate rocks from the Gagra-Java Zone at the transition of the Central Greater Caucasus to the Rioni Basin in Georgia are rare and almost absent in literature. In a joint research project between Georgian and German research institutes, this work showcases the first consistent dataset on rock properties, which are the foundation of the Enguri High Arch Dam, a large and regionally important energy infrastructure. The studied carbonate rocks from a 307 m deep research well are subdivided into two carbonaceous and two dolomitic sections, exhibit intense brecciation, represented by multiple rubble zones. Petrographic analyses in conjunction with petrophysical sample analyses do not show a clear correlation of rock properties to the rock's microfabric. Generally, matrix permeabilities are low to very low (< 10 mD) and do not correlate with matrix porosities. Elevated matrix permeability is only found in samples from the topmost 120 m of the studied well, but is not restricted to samples exhibiting carbonate mineral dissolution (mostly dolomite dissolution), which can be observed along the whole studied well. Based on cathodoluminescence analyses eight distinctly different phases of carbonate cement precipitation in brecciated sections and fractures can be distinguished and related to faulting and compressive tectonic phases resulting in the formation of stylolites. The analyses are supplemented by first UCS measurements (ranging from 19.9-175.0 MPa) to gain a better understanding on the mechanical properties of the studied samples.

Hydropower facilities utilize the potential energy of water to generate electricity, with maximum efficiency achieved when there is a significant topographic gradient between reservoir and turbines. Therefore, high dams are typically built in regions with rugged topography, often associated with (frequently combined) erosion, folding or displacement along fault zones, leading to juxtaposed different material properties. At the Enguri Arch Dam in Georgia, extensive limestone formations from the Cretaceous and Jurassic were thrust southward, resulting in a topography difference exceeding 1000 m between the southward-extending Rioni Basin and the contiguous mountain ranges. The reservoir extends about 25 km to the north. There, nearby mountains reach heights of 3000 m and more. As part of the ongoing crustal shortening process, multiple fault systems have emerged, including prominent SW-NE trending thrust faults, steep strike-slip faults, and to a minor extend normal faults. The Enguri valley carves into the surrounding mountains, reaching an elevation of 280 m above sea level at the dam site. These substantial topographic variations between hilltops and valleys establish a variable initial stress field characterized by lateral heterogeneity in both magnitude and orientation. The initial stress conditions were determined using borehole imaging data and hydraulic fracturing tests, while the mechanical properties of the subsurface materials were evaluated using mechanical tests on core samples. The Enguri high-head Dam has a construction height of 271 m and the Jvari-reservoir reaches at full level more than 510 m above sea level. Geodetic GNSS and seismic stations were installed to evaluate the impact of the annual water level changes of about 100 m on the surrounding area. The subsurface information on stress conditions and material properties was used to create an elastic 3D model of the area. The modelling results were compared with field observations to gain a better understanding of the dynamic processes in the area. In a first step the initial stress field was simulated. Loads were applied to simulate the water level changes. Modelled and observed displacements indicate that rising water level causes the west bank to move north-west, while the east bank moves south-east. Furthermore, both banks of the valley show a downward movement. Conversely, when the water level decreases, the effect is reversed. Variations in water level induce changes in the shear stress and changes in Coulomb Failure Stress (ΔCFS) calculated for different fault orientations. They reveal an increased seismic potential during low water levels, aligning with first seismic observations.

Due to the wide availability of stress measurements in mines it is tempting to infer the regional stress state from stress observations in mines. However, our study demonstrates limitations of this approach and how to overcome them. In this study we used hydraulic fracturing measurement data from shallow boreholes at different mining depth levels in the eastern Ruhr area and compared them with stress information from deep boreholes to infer the regional stress state. We defined selection criteria, which resulted in more robust values for Shmin magnitudes because we eliminated the data that had been influenced by the mine galleries, mining sequence and nearby faults. When deriving SHmax, special consideration was given to the effect of pore pressure. Despite the fact that mines are filled with air, pore pressure cannot be automatically assumed to be zero. The pore pressure in the tested intervals is highly dependent on the excavation damage zone and the permeability of the rock. We show that careful selection of data and consideration of pore pressure (for SHmax values) is essential to distinguish between local and regional stresses in mining areas. We therefore recommend the use of independent pore pressure observations and, where available, deep vertical borehole data. The resulting stress state in our study is indicative of normal fault tectonics, contradicting previous studies that infer a strike-slip tectonic regime. This results in less critical stress states of faults in the study area.

Advance information about local pore pressure distribution is crucial for the drilling of deep geothermal wells. Incorrect adjustment of the drilling mud density leads to drastic differences between wellbore pressure and the ambient pore pressure. Large pressure differences may result in severe drilling problems such as kicks, wellbore instabilities and subsequent partial or full loss of the previous borehole progress. In particular for small geothermal ventures on a communal level, this loss may pose a significant financial risk. We present current work on EFECT, a tool that helps to organize existing pore pressure measurement data and to generate geologically informed pore pressure estimates based on these existing data. EFECT integrates geographic information system (GIS) components that allow the user to explore pore pressure data sets and select offset wells for a planned well location. As a first step, the regional aggregate pore pressure model shows general features of the regional pore pressure with depth. The core feature of EFECT is the projection of the offset wells’ pore pressure to the target well based on matching stratigraphic units. Two projection algorithms are provided that assume either (1) overpressure or (2) vertical effective stress is constant between target and offset wells. EFECT is part of a larger effort to develop a global pore pressure database with a standardized quality ranking. The data from this database, consisting of pore pressure measurements and indicators such as well tests, kicks and mud weight data, provide a standard that users may augment with their own data. This standard data set can be particularly useful for small geothermal ventures. We illustrate EFECT using data from a precursor of the global pore pressure database covering the SE German part of the North Alpine Foreland Basin (Bavarian Molasse Basin).

Knowledge of the recent crustal stress state is crucial for a better understanding of crust stability. However, the amount of available stress data in Germany is low. Therefore, a reliable and comprehensive prediction of the complete stress tensor is not possible with these only. However, 3D geomechanical-numerical models, which represent the geometry of the subsurface and its mechanical properties and are calibrated to stress data, allow a continuum-mechanics based prediction of the complete stress tensor and its lateral and vertical variability. A new geomechanical-numerical model of Germany provides new insights into the recent crustal stress field. In contrast to previous models, an improved geological model with a significantly higher stratigraphic resolution is used, a high vertical resolution of ~40 m allows a better mechanical representation of individual units and mechanical inhomogeneities and new data records are used for calibration. The results provide a comprehensive prediction of the complete stress tensor for Germany and can be used for a wide range of scientific questions and applications. Examples are the prediction of the fracture potential, the slip tendency of faults or as boundary conditions for small-scale models usable for example for engineering applications.

A robust prediction of the present-day stress state is of great importance for the safe usage of the subsurface, e.g., for borehole stability, mitigation of induced seismicity or the search and long-term safety of a high-level nuclear waste deposit. However, the state of knowledge concerning the stress state in Germany is limited as only unevenly distributed stress measurements are available. Two 3D geomechanical-numerical models created during the SpannEnD project (2018-2022) have improved this level of knowledge. Such geomechanical-numerical models - calibrated on available stress magnitudes - enable a continuum-mechanics based prediction of the present-day stress state. In the course of the follow-up project SpannEnD 2.0, a new, significantly improved model provides new insights into the stress state of Germany. The new 3D geomechanical-numerical model combines information of 25 geological models and comprehensive additional data. The final geomechanical-numerical model comprises 52 geological units parametrized with individual mechanical properties (Young’s modulus and Poisson’s ratio) and densities. Linear elasticity is assumed and the finite element method (FEM) is used to solve the equilibrium of forces. Overall, the model contains ~10 million hexahedral elements providing a lateral resolution of 4 x 4 km2 and a vertical resolution of 45 m in the uppermost 5 km. A significantly enhanced stress magnitude database has been used for model calibration on magnitudes of the minimum (Shmin) and maximum horizontal stresses (SHmax). The model results show an overall good fit with these stress magnitudes indicated by a mean of the absolute stress differences of ~5 MPa for Shmin and SHmax. Furthermore, our results agree well with additional data sets not used for calibration, e.g., an absolute mean deviation of the orientation of SHmax with regard to World Stress Map data of ~10°.

The cessation of hard coal mining in the Ruhr Basin in 2018 marked the region's transition to the post-mining phase. Controlled mine water rebound induces changes in the subsurface stress conditions, as pore pressure increases locally. Presently, mine water rebound is observed in the eastern Ruhr Basin (water province “Haus Aden”) along with associated microseismicity. Furthermore, post-mining challenges might comprise the potential risk of fault reactivation, which is addressed in this study by conducting a fault slip assessment.Based on subsurface coal seam mapping data, a 3D structural model for the NE part of the “Haus Aden” water province has been constructed to serve as the basis for identifying the most vulnerable fault trends and types of the structural inventory. Slip tendency analysis, considering normal faulting conditions, revealed NW-SE to NNW-SSE trending normal faults to be most susceptible to reactivation. Probabilistic fault slip assessment, focused on NW-SE to NNW-SSE trending normal faults mapped within the “Heinrich-Robert” colliery, show no fault reactivation potential for a mine water rebound up to a level of 640m below ground. Assuming hydrostatic conditions in the vicinity of the faults, friction coefficients are only partially exceeded for high differential stresses.In addition, a novel workflow is used to model the spatial variability of the frictional fault strength as input for a fault stability analysis, exemplified for a selected NNW-SSE trending normal fault. For considering hydrostatic pore pressure, results show that the fault consists mainly of stable, but also unstable, horizontally elongated patches. These findings question the conventional simplified approach of using a single constant friction coefficient for fault stability analysis.

At the Enguri Arch Dam, research on methods for a comprehensive monitoring system has been ongoing since 2019. The aim is to identify correlations between different processes and mechanisms, to derive recommendations for the safe operation of the facility. Historical and operational data as well as the results of new measurements will serve as the basis for the analysis. In addition to established methods, new concepts such as the successful testing of GB-SAR for dam deformation monitoring have been implemented and Artificial intelligence (AI) methods will be used.

The contemporary crustal stress state is primarily driven by gravitational volume forces and plate tectonics. However, there are various smaller-scale sources such as geological structures and stiffness contrast that perturb stresses and deviate them from the regional pattern. For example, borehole stress analysis in numerous cases has revealed abrupt rotations of horizontal stress orientation of up to 90° when faults are crossed. Herein, we investigate the rotation of principal stress axes at a fault by means of a 2D generic numerical model. We focus on the near field of the fault and the damage zone with a fault parameterized as a rock stiffness contrast. A substantial influence of the far-field stress field in terms of the differential stress and in terms of the stress ratio RS=S1/S_3 is shown. Furthermore, the contrast in material properties is the basis for any stress rotation, and in particular the stiffness is demonstrated to have a significant influence. Eventually, the impact of the angle between the fault strike and the orientation of SHmax is demonstrated. Our results show that the stress rotation is negatively correlated with the ratio of principal far-field stresses. A small angle between the far-field stress orientation and the fault facilitates stress rotation. A high contrast in rock stiffness further increases the stress rotation angle. Faults striking perpendicular to the maximum principal stress orientation experience no rotation at all. However, faults oriented parallel to the maximum principal stress orientation experience either no rotation or a 90° rotation, dependent on the ratio of principal stresses and the rock stiffness contrast. A comparison with observations from various boreholes worldwide shows that in general the findings are in agreement, even though the dip angle proves to have an influence on the stress rotation, in particular for shallow-dipping faults.

Abstract. Even though the crustal stress state is primarily driven by gravitational volume forces and plate tectonics, interpretations of borehole breakout observations show occasionally abrupt rotations of horizontal stress orientation of up to 90° when faults are crossed. This indicates the influence of faults on the local stress state, which parameter control the degree of rotation. Herein, we investigate the phenomenon of principal stress rotation at a fault by means of a 2D generic numerical model. We parametrised the fault as a rock stiffness contrast and investigate systematically the full model parameter space in terms of the ratio of the applied principal stresses, the rock stiffness contrast, as well as the angle between fault strike and orientation of the principal stress axis. General findings are that the stress rotation is negatively correlated with the ratio of principal stresses. A small angle between the far field stress orientation and the fault facilitates stress rotation. A high contrast in rock stiffness further increases the stress rotation angle. Faults striking perpendicular to the maximum principal stress orientation experience no rotation at all. However, faults oriented parallel to the maximum principal stress orientation experience either no rotation or a 90° rotation, dependent on the ratio of principal stresses and the rock stiffness contrast. A comparison with observations from various boreholes worldwide shows that in general, the findings are well in agreement, even though the dip angle proves to have an influence on the stress rotation, in particular for shallow dipping faults.

To gain information on the regional tectonic state of stress in an area it is important to separate it from stresses affected from anthropogenic activities such as the construction of tunnels or mines. The Ruhr region is characterised by centuries of mining. To ensure safe operations, large-scale hydraulic fracturing campaigns were carried out in several mines at the end of the last century. This study provides a compilation of the regional state of stress in the Ruhr area based on the mine measurements which have been reassessed to deduce the regional stress component and to compare that with stress orientations from independent sources (deep borehole stress information and earthquake focal mechanisms). As orientations of both data sets agreed well the selected stress data of the mines have been combined with the borehole and earthquake data and a mean orientation of the maximum horizontal stress, S-Hmax, of N154 degrees was obtained for the Ruhr area. The spatial distribution of the stress orientations in the Ruhr area shows a rather homogeneous stress pattern with only very few locations where stress orientations differ significantly from the average.

Abstract. Fault reactivation potential is a crucial aspect for many underground utilizations, such as the construction and long-term safety of a nuclear waste repository, as seismic events can endanger these operations. An estimation of the fault reactivation potential requires information about the stress field, but stress data are only available pointwise and are not evenly distributed throughout Germany. Geomechanical–numerical modeling can be used to derive a spatially continuous description of all six independent components of the stress tensor as shown by the model of Germany by Ahlers et al. (2022). Information about the geometry of faults extending several kilometers in depth is provided for most areas in Germany by the geological models of the federal states and geological models created in the framework of projects such as GeoMol (Assessing subsurface potentials of the Alpine Foreland Basins for sustainable planning and use of natural resources) or GeORG (Geopotenziale des tieferen Untergrundes im Oberrheingraben). We use the 3D fault geometries provided by such models and map the stress data from the Germany model by Ahlers et al. (2022) onto these faults. Then, assuming hydrostatic pore pressure, we calculate the so-called slip tendency (TS), the ratio between resolved shear stress and the effective normal stress on the fault plane as a measure of fault reactivation potential. A fault is considered critical when its TS value exceeds its coefficient of friction. In general, TS ranges between 0 and 0.7 for the analyzed faults. The highest overall TS values are observed along the NNE–SSW-striking Upper Rhine Graben, where TS routinely reaches and exceeds values of 0.7. In the North German Basin, the Ore Mountains and Saxony only very few TS values exceed 0.7. The area with the lowest overall TS is the Molasse Basin, where the TS of the mostly WSW–ENE-striking faults only rarely exceeds values of 0.4. In general, N–S- to NNE–SSW- and NW–SE-striking faults show the highest TS values, whereas WSW–ENE-striking faults show the overall lowest values. With increasing depth, TS decreases. Pore pressure and overpressure have the potential to significantly influence the resulting TS.

For many underground operations such as geothermal energy exploitation, mining, oil and gas production or the storage of high-level radioactive waste, active tectonic or induced seismicity is of concern. Seismicity usually occurs on pre-existing faults that are reactivated under adequate stress conditions. Thus, an assessment of the reactivation potential of faults can aid in the identification of areas particularly prone to the occurrence of seismic events or such areas where adequate geotechnical measures have to be taken to avoid anthropogenic fault reactivation. A tool for the assessment of the fault reactivation potential is the so called slip tendency, which is the ratio between the maximum resolved shear stress on the fault plane and the normal stress. Such an analysis requires information about the stress field acting on the fault plane and information about the fault geometry, fault orientation and frictional properties. Information about these parameters can be very limited, since 3D fault geometries are often only extrapolated from geological surface data. Furthermore, stress data is usually sparse, only available pointwise and unevenly spatially distributed. Geomechanical-numerical modelling can be used to derive a spatially comprehensive description of all six independent components of the stress tensor from the available stress data. For Germany, an estimate of the stress tensor is provided by the geomechanical-numerical model by Ahlers et al. (2022). Furthermore, fault geometries as part of geological models of the German federal states are available for large parts of Germany. We use both the stress data derived from the geomechanical-numerical model and the fault geometry data from the federal state models to calculate slip tendencies for more than 10.000 faults and fault segments. The resulting slip tendency is generally the highest in the northern Upper Rhine Graben area where it routinely reaches values of 0.7 and more. In the Alpine and Alpine Foreland region the slip tendency is generally the lowest with values only very rarely exceeding 0.3. In North Germany slip tendency values range mainly between 0.3 and 0.6 but with both higher and lower values being fairly common. In general, faults striking in NNE-SSW direction and NW-SE direction display the overall highest slip tendencies whereas faults striking in ENE-WSW direction show very low slip tendencies. With increasing depth slip tendencies generally decrease strongly. However, there are still major areas in Germany where either no fault geometries or only insufficient fault geometries are available. Furthermore, pore pressure has a major influence on the slip tendency. For our calculations, we assume hydrostatic pore pressure. While overpressured pore fluid is documented for example for the Molasse Basin in South Germany, no spatially comprehensive pore pressure data set is currently available for the whole of Germany.