This session aims to bring together researchers from different fields to explore and compare methodologies for investigating fractured rock masses, emphasising the value of integrated multi-scale (from grain-scale microcracks to meso-scale fracture networks, up to tectonic-scale systems) and multidisciplinary approaches.
We welcome contributions across a broad geological and process-based context, linking observations and methods from field-based surveys, outcrop characterisation, laboratory testing, microstructural analysis, numerical and analogue modelling, remote sensing, and geophysical imaging. Applications to natural hazards (e.g., rockfalls, landslides), energy and resource exploration, fluid transport and storage, structural geology and tectonics, are particularly encouraged. By bringing together structural geology, rock mechanics, and engineering geology, the session aims to foster a constructive and stimulating discussion on fractures across scales and disciplines, addressing both scientific and practical challenges.
Orals: Mon, 4 May, 16:15–18:00 | Room -2.20
The geometry and kinematics of small faults within relay ramps are affected by local stress perturbations due to coeval propagation of laterally overstepping normal faults with negligible separations. Independent of their stepping sense and relative fault slip rates, previous studies documented the high structural complexity of carbonate relay ramps cropping out in central Italy, where Mesozoic carbonates of the Lazio-Abruzzi Platform are crosscut by an active extensional fault system. Notably examples include the ~400 m-wide, ~900 m-long relay ramp within the Tre Monti fault dissected by small faults with variable attitudes and kinematics showing values of fault and fracture density peaks in its middle portion. Similarly, the ~3 km-wide, ~7km-long relay ramp bounded by the Venere-Gioia dei Marsi and Pescina-Parasano normal faults exhibits the highest amount of extensional strain within its central portion.
In order to gain new insights on the possible role of surface geometry of the main slipping planes on the spatial distribution of fault-related damage, we focus on the ca. 8 km-long, 110 m-offset, NW-SE striking and SW-dipping Monte Capo di Serre fault. This fault displaces Mesozoic-Tertiary platform carbonates and Pleistocene slope debris, and it is continuously exposed along a ~800 m-long along-strike outcrop. Studying a ~60 m-long and 32 m-wide relay ramp bounded by 100’s m- long fault segments forming a sinistral overstep, and at smaller scale a 9 m-long, 5 m-wide relay ramp bounded by 10’s of m-long dextral overstepping slip surfaces we first conduct field and digital structural analyses and then fault roughness analysis.
Results show that the slickenside attitude and kinematics are controlled by overstep geometry. In fact, dextral oversteps are associated with NNW-SSE to N-S striking high-angle slickensides recording pure-dip slip extension, whereas sinistral oversteps are characterized by ESE-WNW to E-W striking, moderate-angle slickensides recording left-lateral transtension. Independently of the overstep geometry, results of spectral analysis of the outcropping slickensides indicate they are significantly rougher (root mean square roughness, Rq≈25-68 mm) within relay ramps than along the main slip surfaces (Rq≈1 mm). Integration with microstructural observations suggests that the relay ramps localized diffuse post-seismic deformation and aftershock-related fracturing, as recorded by diffuse host rock brecciation and widespread fracturing. Conversely, the main slip surfaces predominantly accommodated seismic slip, as shown by truncated clasts and multiple generation of cataclasite and ultracataclasite layers. We argue that these results support the interpretation that fault-surface roughness within carbonate relay ramps might exert a primary control on local stress perturbations, thereby contribution to their complex structural and kinematics complexities.
How to cite: Agosta, F., Dastoli, S., Taddeo, C., Abdallah, I., Curzi, M., Mercuri, M., and Corradetti, A.: Structural complexity and fault roughness properties of carbonate relay ramps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4008, https://doi.org/10.5194/egusphere-egu26-4008, 2026.
To clarify the migration characteristics of the X Sag trough in the Zhuyi depression of the Pearl River Mouth Basin and understand the distribution patterns of hydrocarbon source rocks, this study employs newly processed high-resolution 3D seismic data and integrates techniques such as fault activity period determination, fault displacement-distance curve analysis, and balanced section methods. It systematically investigates the deformation mechanism of the X Sag Fault in the Zhuyi Depression and its control over hydrocarbon source rock distribution. The study reveals: ① The X Sag is a north-dip, south-lobe scoop-shaped half-graben controlled by the NE-NEE-NWW multi-trend arc-shaped F1 fault, with three sets of secondary faults (NE, NEE, EW) developing within the depression. Based on the segmentation characteristics of the main boundary fault F1 and its combination patterns with secondary faults, the study area is divided into eastern and western sub-basins. ② The X Sag underwent multiple phases of tectonic evolution under the influence of multi-phase, multi-directional stress fields, primarily comprising four stages: Fracture Stage I, Fracture Stage II, Fracture Stage III, and the Tilting Stage. Based on the long-term activity characteristics of the main boundary fault F1 and the activity features of different phases of the secondary faults within the sag, five sets of fault systems were delineated: faults active only during the Early Wenchang Period, faults active during the Early Wenchang-Enping Period, faults active during the Late Wenchang-Enping Period, faults active only during the Enping Period, and long-term active faults. ③ The secondary faults within the X Sag are collectively controlled by a pre-existing arc-shaped NE-NEE-NWW-trending reverse-transform fault system. During basin formation, the western sub-sag underwent extensional deformation along pre-existing NE-NEE-trending faults, forming a series of secondary faults aligned with the main boundary fault strike. These appear in cross-section as structures reverse-cutting the main boundary fault. Conversely, the eastern sub-sag underwent extensional-torsional deformation along pre-existing NWW-trending strike-slip faults, generating a series of near-EW-trending secondary faults. During deformation, a “V”-shaped structural pattern formed in the profile. ④ The segmented growth and differential activity characteristics of different control-depression faults within the basin governed the migration of the depression trough sedimentary center from northwest to southeast and from the basin margin toward the basin interior, thereby influencing the distribution of hydrocarbon source rocks during the Early and Late Wenchang periods.
How to cite: Sun, X., Sun, Y., and Chen, F.: Deformation Mechanism and Its Depression Controlling-Source Controlling Effect of X Sag Fault System in Pearl River Mouth Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2947, https://doi.org/10.5194/egusphere-egu26-2947, 2026.
Strike-slip faults critically control hydrocarbon migration in the Mesozoic clastic reservoirs of the Tahe Oilfield, NW China. However, their identification is challenged by weak seismic responses due to subtle impedance contrasts, steep dips, and small throws. This study conducts a systematic, multi-method comparison to optimize fault detection, evaluating both conventional seismic attributes and a novel deep learning (DL) approach.
We first applied structure-oriented filtering to enhance data continuity. Subsequently, key conventional attributes were computed: coherence and curvature to delineate major structural discontinuities and flexures, ant tracking to highlight fault pathways, and likelihood to map fault lineaments. The core of our DL approach involved a ResU-Net model, pre-trained on extensive datasets and refined via transfer learning using 65 manually interpreted fault traces from the target area. This process generated a high-resolution fault probability volume.
Results from the key T34 horizon demonstrate a clear performance hierarchy. While coherence and curvature effectively image major faults, they lack resolution for secondary networks. Ant tracking and likelihood show sensitivity to small-scale features but suffer from poor continuity and noise. In stark contrast, the AI probability volume integrates the strengths of these methods, simultaneously providing superior boundary clarity for major faults and enhanced detection of subtle, secondary strike-slip faults crucial for hydrocarbon migration. It presents a more continuous, spatially coherent, and geologically plausible 3D fault system.
This work underscores the significant advantage of an AI-driven, integrated workflow over individual conventional attributes. It provides a robust, scalable template for multi-scale fracture characterization in complex reservoirs, effectively bridging the gap between geophysical data analysis and geological interpretation.
How to cite: Jiang, Y. and Han, C.: Characterizing Mesozoic Strike-Slip Faults in China's Tahe Oilfield: A Multi-Method Comparison from Traditional Seismic Attributes to AI, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2170, https://doi.org/10.5194/egusphere-egu26-2170, 2026.
LA-ICP-MS U–Pb geochronology of syn-kinematic calcite in faults and fractures provides a direct means of dating brittle deformation. We present U–Pb calcite geochronological data from deformation features across a range of scales—stylolites, veins, minor faults, and major thrusts—within the Provence fold-and-thrust belt. Whether in thrust-related cover folds (Mirabeau and Bimont) or in the more complex Nerthe Massif, the results illustrate how calcite geochronology can enhance or challenge our understanding of fracture pattern development in reservoirs.
Calcite geochronology validates the sequence of fracture development during layer-parallel shortening, fold growth, and late-stage fold tightening, previously inferred from structural orientations and cross-cutting relationships, regardless of fold type. Dating of calcite jogs formed at the tips of sedimentary or tectonic stylolites further constrains the timing of deformation stages. Geochronology also helps differentiate local from regional deformation by defining a more precise chronological framework where other geological markers are absent.
Across all investigated structures, deformation features show remarkable age consistency and slight overlaps between stages, providing a continuous and detailed record of fracture development. The age overlaps may indicate that deformation lasted less than the analytical uncertainty or that fracturing was more continuous throughout folding and thrusting than previously assumed. The consistency of ages across structural scales suggests either coeval deformation or events too close in time to be distinguished by U–Pb dating. This observation supports the syn-kinematic nature of calcite mineralization in small tectonic veins, even where infills display blocky, non-stretched textures. While precipitation may lag slightly behind fracture opening in individual veins, at the vein-set scale, both processes remain coeval within dating resolution. This broadens the applicability of U–Pb calcite geochronology to diverse mesoscale structures.
The dataset reveals the multi-phase development of similarly oriented fractures, which possibly initiated during burial and were reopened or densified during subsequent tectonic episodes. Geochronology provides a robust way to test whether fractures grouped by orientation, deformation mode, and relative chronology (‘fracture sets’), as well as classical associations of veins, stylolites, and conjugate faults defined by kinematic and mechanical compatibility, truly reflect the same deformation event. Veins with up to 60° strike variation sometimes yield indistinguishable ages (within a few Myr), challenging conventional definitions of fracture sets and implying local stress variations. This questions the presumed stability of the stress field in tectonic reconstructions.
Regionally, clusters of U–Pb calcite ages, if not reflecting sampling bias, hint towards variations in fluid activity, redox conditions, and/or uranium mobility, or distinct pulses of brittle rock damage and fluid flow. The latter interpretation suggests two deformation phases—late Cretaceous (81–67 Ma) and late Paleocene–Eocene (59–34 Ma)—separated by a Paleocene tectonic quiescence, matching the two already recognized Pyrenean shortening phases and indicating a likely, though not systematic, link between regional tectonic activity, brittle rock damage, fluid circulation, and calcite mineralization.
These examples demonstrate how U–Pb calcite geochronology not only constrains the timing and duration of brittle deformation but also helps reassess models of fracture development and fold–fracture relationships.
How to cite: Lacombe, O., Beaudoin, N., Zeboudj, A., Callot, J.-P., Lamarche, J., Hoareau, G., Guihou, A., and Deschamps, P.: Refining the picture of fracture development in folded carbonate reservoirs : Insights from U-Pb geochronology of syn-kinematic calcite mineralizations in the Provence fold-and-thrust belt, France , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4842, https://doi.org/10.5194/egusphere-egu26-4842, 2026.
Tectonic fractures refer to a series of discontinuities formed in crustal rocks under the action of tectonic stress, serving as a key factor governing numerous geological processes and resource exploitation. In the field of oil and gas exploration, especially for the tight sandstone reservoirs in the Kuqa Depression of the Tarim Basin, the tectonic fracture system acts as the primary seepage pathway and reservoir space, directly determining the distribution of reservoir "sweet spots" and single-well productivity. To achieve quantitative characterization of reservoir fractures and accurate prediction of their spatial distribution, we innovatively introduced the principle of minimum energy dissipation and the principle of least action, which reflect the essential laws of nature. By fully integrating the complex tectonic evolution process with classical mechanics theory, we completed the quantitative prediction research on fractures during complex tectonic evolution based on four-dimensional (4D) dynamic stress field simulation. Based on the analysis of tectonic evolution history in the Keshen 8 area of the Kuqa Depression, combined with extensive field, seismic, core and logging data, as well as rock mechanics experiments and acoustic emission experiments, a reasonable paleotectonic geomechanical model was established. From a novel perspective, we introduced the principle of minimum energy dissipation and the principle of least action, and further combined them with classical mechanics theory and the variational principle of continuum media. A time-domain dynamic rock failure criterion and a fracture parameter characterization model were constructed, building a "bridge" between stress and fracture parameters. By selecting an optimal elastoplastic finite element simulation platform and setting appropriate time steps, we completed the time-domain 4D tectonic stress field simulation. On this basis, we implanted Python programs into the finite element simulation platform, realizing the quantitative prediction of the spatial distribution of reservoir fractures in the Keshen 8 area of the Kuqa Depression. The prediction results indicate that folding is the primary controlling factor for fracture development in the Keshen 8 gas reservoir. On the plane view, the linear fracture density in the structural high parts of the east-west anticlines is slightly higher than that in the saddle parts and both limbs, and the linear fracture density in the core of the eastern anticline is higher than that of the western anticline. The fracture dip angle gradually decreases from the structural high points to the two limbs of the anticlines. The prediction results are in high agreement with the actual well-point measurement data and production performance data. High-yield wells are basically located in fracture-developed zones with high linear density and near-vertical dip angles.
How to cite: Liu, S., Wang, G., and Feng, J.: Quantitative Prediction of Tectonic Fractures Coupled with Minimum Energy Dissipation and Least Action Principles: A Case Study of Keshen 8 Area, Kuqa Depression, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3308, https://doi.org/10.5194/egusphere-egu26-3308, 2026.
This study investigates how local stress state governs permeability magnitude in fractured carbonate aquifers. By using outcrop-constrained Discrete Fracture Network (DFN) modelling from Mt. Viggiano of the southern Apennines, Italy, we investigate the control exerted by 500 m-depth tri-axial local stress state on computed horizontal permeability anisotropy. Fractured carbonate systems commonly exhibit strong permeability anisotropies that evolve with depth as fractures respond to changes in both normal and shear stresses. Accurately capturing this behaviour remains challenging due to the combined effects of fracture geometry and connectivity, as well as primary depositional architecture and stress-dependent aperture modification.
Field-derived fracture datasets from four carbonate outcrops representing two contrasting paleo depositional settings are used to construct three-dimensional DFN models at the bed-package scale. Two DFN-based modelling workflows are employed to explore how different representations of fracture connectivity and flow influence predicted permeability. One approach estimates bulk permeability from fracture population statistics within distinct geocellular volumes. Differently, the other one explicitly simulates steady-state fluid flow through hydraulically connected fracture networks within a fully meshed computational domain. This integrated strategy allows evaluation of how modelling assumptions related to connectivity, aperture scaling, and flow representation affect permeability predictions without implying a preferred modelling tool.
The results of this study show that increasing normal stress generally reduces horizontal permeability anisotropy, although local increases in permeability occur where favourably oriented fractures undergo shear induced dilation. Result are also consistent with the permeability response varying systematically with depositional architectures: (i) massive, high-energy carbonates dominated by non-strata bound fractures exhibit vertically persistent but weakly connected networks; (ii) on the contrary, layered, low-energy carbonates containing abundant strata-bound fractures display enhanced lateral connectivity and higher hydraulic effective transmissivity.
The main outcomes of this work demonstrate that permeability anisotropy in fractured carbonates evolves with stress through its interaction with fracture orientation, connectivity, and stratigraphic architecture. Incorporating stress dependent behaviour and explicit connectivity into DFN workflows therefore improves predictions of subsurface fluid flow relevant to groundwater resources, CO₂ storage, and geothermal systems.
How to cite: Abdallah, I. B., Healy, D., Hyman, J., Prosser, G., and Agosta, F.: Permeability Anisotropy in Fractured Mesozoic Platform Carbonates under Variable Triaxial Stress Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5148, https://doi.org/10.5194/egusphere-egu26-5148, 2026.
Shale oil reservoirs are typically characterized by ultra-low porosity and permeability, in which natural fractures provide key pathways for hydrocarbon migration from the matrix to the wellbore. These fractures significantly influence production performance. In the Mahu Sag of the Junggar Basin (NW China), the Permian Fengcheng Formation comprises saline lake–facies mixed shales with limited primary porosity, where natural fractures and dissolution pores dominate the available storage space. The sustained high single-well production (exceeding 100 t/day in parts of the sag) underscores the importance of understanding fracture occurrence and effectiveness for efficient reservoir development. In this study, we interpret Full-bore Micro-scanner Imager (FMI) borehole image logs using Schlumberger Techlog to identify and quantify both drilling-induced and natural fractures. The results show that drilling-induced fractures, which appear as short vertical features with symmetric “feather” or en-echelon patterns, are used to infer the orientation of the current maximum horizontal stress (SHmax). SHmax varies across structural domains: it trends near E–W to ENE–WSW adjacent to the Wuxia fault belt, shifts locally toward NE–SW at the junction of the Wuxia and Kebai fault belts, and transitions back to ENE–WSW to E–W toward the southwestern and southernmost regions. Natural fractures are abundant, predominantly striking NE–SW and near E–W (40°–100° and 220°–280°, accounting for 51% of fractures), with a secondary set trending NNW–SSE (140°–160° and 320°–350°, accounting for 22%). These orientations largely align with major fault trends. Fracture dip distributions vary significantly between wells and are primarily controlled by bedding attitude, with the apparent dip deflection closely mirroring the formation dip. In proximity to faults, tectonic fractures tend to exhibit lower dips. Aperture statistics reveal that fracture effectiveness is strongly stress-dependent: fractures more closely aligned with SHmax exhibit larger apertures and higher inferred effectiveness, while aperture size decreases with increasing misalignment angle. In a representative well, ENE–WSW fractures exhibit the largest mean apertures (tens of micrometers) compared to other fracture sets. Overall, SHmax) in the Fengcheng Formation shale is predominantly oriented E–W to ENE–WSW, and natural-fracture trends broadly match the strikes of major faults. Fracture dip angles are largely governed by bedding attitude, whereas fracture effectiveness is strongly stress-dependent. These results provide a direct basis for sweet-spot evaluation (targeting intervals with larger apertures under more favorable stress conditions) and for optimizing stimulation orientation and treatment design.
How to cite: Du, X. and Zeng, L.: Present-day stress control on natural fracture effectiveness: quantitative evidence from borehole image logs in the Fengcheng Formation shales, Mahu Sag, Junggar Basin, NW China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21984, https://doi.org/10.5194/egusphere-egu26-21984, 2026.
The Tuscaloosa Marine Shale (TMS) is an unconventional play in southwestern Mississippi and southeastern Louisiana characterized by a well-developed network of natural fractures that strongly influences reservoir behavior and hydraulic fracturing performance. The play is significant to the energy industry due to its substantial hydrocarbon resources—estimated at approximately 1.5 billion barrels of oil and 4.6 TCF of gas—and its proximity to existing infrastructure. Although more than 80 wells have been hydraulically fractured in the formation, producing a total of 13.82 million barrels of oil and 9.04 BCF of gas, development remains challenging due to the shale’s high clay content, complex mineralogy, and the poorly constrained impact of natural fractures on production.
This study employs an integrated workflow to characterize natural fractures in the Tuscaloosa Marine Shale using electrical borehole image logs, shear-wave splitting data, and core descriptions from seven wells distributed across the play. The analysis indicates that the natural fractures are predominantly vertical to subvertical extension fractures, commonly fully mineralized, with heights ranging from 1 to 3 feet. These fractures preferentially trend east–west, are associated with calcite-rich intervals, and are capable of transecting the entire borehole. Smaller fractures often terminate at lithological boundaries but commonly reactivate along parallel planes.
The proposed methodology provides critical insight for optimizing hydraulic fracturing design by identifying stress orientation and optimal lateral placement relative to natural fracture distribution. In one lateral well alone, approximately 500 closed fractures were identified. Furthermore, the maximum horizontal stress orientation is shown to be consistent across the formation and aligned with the regional stress regime of the Gulf Coast Basin.
How to cite: Ruse, C. M. and Mokhtari, M.: Natural Fractures of the Tuscaloosa Marine Shale, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13667, https://doi.org/10.5194/egusphere-egu26-13667, 2026.
The structural architecture of the Eastern Province of Saudi Arabia is defined by a complex interplay between localized halokinesis and regional compressional stresses. This study provides a comprehensive geological investigation into the mechanical and tectonic linkages between the heavily fractured Late Miocene-Pliocene Hofuf Formation and the Eocene Rus Formation situated at the apex of the Dammam Dome. Historically, these two units have been studied as distinct stratigraphic entities; however, this analysis integrates field observations from Jabal Al-Shuʿba with regional geophysical data to demonstrate a shared deformation history. The Dammam Dome, an oval-shaped structure covering approximately 500 km, is cored by the Infracambrian Hormuz Salt. Its diapiric rise, occurring at rates of up to 7.5 m/Ma during the Neogene, induced a systematic fracture network in the Rus Formation characterized by radial and concentric Mode I tension joints. Concurrently, the Arabian Plate's collision with Eurasia, the Zagros Orogeny, transmitted far-field intraplate stresses that reactivated these older structural grains. Field data from the Hofuf Formation at Jabal Al-Shuʿba reveal a high-intensity, multidirectional fracture system within alternating sandstone and mudstone beds. Unlike the uniform patterns observed at the Dammam Dome apex, the Hofuf fractures exhibit bimodal and conjugate orientations (NNE-NE and NW-SE) with apertures reaching 15 cm. This disparity is attributed to mechanical stratigraphy; the bed-bounded nature of fracturing in the clastic Hofuf Formation prevents the stress relief found in the massive Eocene carbonates, leading to increased fracture density. Furthermore, the identification of a soft-sediment detachment within the Rus Formation suggests that the Dammam Dome served as a sensitive stress sensor for the initial stages of the Zagros collision. By establishing a structural bridge between the Eocene and the Neogene, this study explains how salt-induced uplift and plate-scale compression have combined to create the heavily fractured landscape of Al-Ahsa. These findings offer critical insights for reservoir characterization, groundwater flow modeling, and urban geomechanical stability in the region.
How to cite: Osman, M.: Integrative Structural Evolution of the Eastern Arabian Platform: Decoupling Salt-induced Halokinesis and Zagros-related Compression in the Fractured Neogene and Paleogene Successions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5893, https://doi.org/10.5194/egusphere-egu26-5893, 2026.
Posters on site: Tue, 5 May, 10:45–12:30 | Hall X2
Crystalline rocks are typically low in porosity, but they often contain fractures, which provide critical pathways for fluid flow and influence groundwater storage, resource estimation, and safety assessments for nuclear waste repositories. Despite their importance, effective fracture porosity in crystalline rocks remains poorly constrained due to limited and regionally biased measurements. In this study, we used global permeability datasets and modified an existing equation to estimate porosity from permeability, incorporating fracture roughness and aperture. This allowed us to calculate nearly 28,000 porosity values across a wide range of depths and geological settings. The resulting porosity distributions are highly right-skewed and show an exponential decrease with depth. Our findings indicate that porosity values in crystalline rocks are generally lower than previously assumed. Median porosity values in the upper 100 meters are several orders of magnitude lower than the commonly assumed 1% porosity, highlighting a significant discrepancy between our estimates and traditional assumptions. We quantified uncertainty using Monte Carlo simulations, which show that natural variability in porosity dominates over parameter uncertainty, underscoring the robustness of our global trends. These findings imply that groundwater storage in crystalline rocks is far smaller than previously estimated, and groundwater velocities may be higher than predicted by models assuming larger porosity, with implications for contaminant transport and nuclear waste safety.
How to cite: van den Berg, J. and Luijendijk, E.: Effective fracture porosity in crystalline rock, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3360, https://doi.org/10.5194/egusphere-egu26-3360, 2026.
Quantitative characterisation of the geometrical properties of discontinuities in fractured rock masses is fundamental for understanding their mechanical behaviour, structural characterisation, and for performing reliable rockfall susceptibility assessments. Discontinuity abundance parameters, such as intensity and density, play a key role in rock mass classification and hazard analysis. Yet, accurately estimating them remains challenging due to limited accessibility, scale effects, and censoring bias in conventional field surveys.
Recent advances in remote sensing techniques, particularly UAV-based digital photogrammetry, enable the acquisition of high-resolution three-dimensional point clouds and ortho-view images, commonly referred to as Digital Outcrop Models (DOMs). These datasets significantly improve access to steep or unstable rock faces and enable detailed, reproducible discontinuity mapping. However, standardised, open-source tools for the quantitative analysis of discontinuity abundance from 2D ortho-view images remain limited.
Here, we present a new toolbox within the open-source MATLAB application QDC-2D (Quantitative Discontinuity Characterization, 2D) (Loiotine et al., 2021), focused on the calculation and spatial visualization of discontinuity abundance parameters. The toolbox computes commonly used linear (P10) and areal (P20, P21) discontinuity intensity and density metrics using two approaches. It uses well-established Mauldon estimators (Mauldon et al., 2001) and introduces a circular scan window approach that improves fracture intensity and density estimation through direct calculation of discontinuity trace segment lengths and number within the circular scan window. The toolbox further allows user-defined regions of interest (ROI) and cluster-based abundance calculation to capture spatial variability in discontinuity density and intensity. This approach enables the detection of high-fracturing zones with high certainty.
The toolbox's capabilities have been thoroughly tested and validated using multiple synthetic discontinuity datasets, demonstrating robust, reliable performance. This extension toolbox for QDC-2D provides a reproducible, accessible framework for quantitative discontinuity analysis, thereby supporting improved structural characterisation of fractured rock masses.
References:
Mauldon, M., Dunne, W. M., & Rohrbaugh, M. B., Jr. (2001). Circular scanlines and circular windows: New tools for characterizing the geometry of fracture traces. Journal of Structural Geology, 23(2–3), 247–258.
Loiotine, L., Wolff, C., Wyser, E., Andriani, G. F., Derron, M.-H., Jaboyedoff, M., & Parise, M. (2021). QDC-2D: A Semi-Automatic Tool for 2D Analysis of Discontinuities for Rock Mass Characterization. Remote Sensing, 13(24), 5086. https://doi.org/10.3390/rs13245086
How to cite: Lukačić, H., Wolff, C., Krkač, M., and Jaboyedoff, M.: New Integrated QDC-2D Toolbox for 2D Discontinuity Abundance Calculation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3968, https://doi.org/10.5194/egusphere-egu26-3968, 2026.
Fracture networks characterization is fundamental for assessing the stability of engineered slopes; although fractures are primary drivers of rock mass behavior, capturing their complexity across scales remains a significant challenge. This study presents a multidisciplinary workflow that integrates field-based geological interpretation with advanced remote sensing and numerical modeling to characterize fractured rock slopes. While recent progress in Remotely Piloted Aircraft Systems (RPAS) and Structure from Motion (SfM) has optimized 3D data acquisition, a gap persists in standardizing the transition from Digital Outcrop Models (DOMs) to representative geomechanical models, such as the rock block volume (Vb).
To bridge this gap, we propose an integrated workflow that compares and integrates results from field surveys, DOM and Discrete Fracture Networks (DFNs). By moving beyond traditional analyses (e.g., Markland Test and ISRM suggested approaches), which often oversimplify spatial complexity, our approach leverages high-resolution 3D data to improve the identification and prioritization of critical structural features. This framework was applied to the Molassana quarry (Genoa, Italy) as part of the SkyMetro project, demonstrating how us a multi-methodological workflow provides a more robust, data-driven assessment for large-scale engineered fracture slopes.
How to cite: Foletti, M., Menegoni, N., Poggi, E., Benedetti, G., Comedini, M., Elmo, D., and Maino, M.: A multi-methodological workflow for fractured rock slope stability and block volume estimation , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20377, https://doi.org/10.5194/egusphere-egu26-20377, 2026.
Understanding the processes that govern fracture development in upper crustal rocks is crucial for characterizing the mechanical response of the Earth’s crust. While conventional failure criteria capture many aspects of fracturing observed in laboratory experiments, they fall short in explaining how system-spanning fractures emerge from the interaction and coalescence of microcracks distributed throughout a deforming rock mass. Additionally, empirical rupture models rarely distinguish the relative roles of tensile and shear mechanisms in macroscopic failure. In this study, we explore the influence of the geometrical arrangement of pre-existing microcracks on fracture formation by analyzing the elastic stress perturbations they generate, employing two-dimensional Finite Element Method (FEM) simulations. This approach allows us to quantify how cracks with different orientations modify the surrounding stress field, producing localized zones of elevated tensile and/or shear stress that may act as favorable pathways for fracture propagation. By systematically varying microcrack orientation and distribution, we can map how stress concentration patterns interact, providing a framework for understanding fracture coalescence in heterogeneous rock materials. Our results reveal that the orientation and spatial arrangement of pre-existing microcracks dictate the directions and magnitudes of stress perturbations, creating preferential trajectories for system-spanning fractures. In particular, regions of high tensile and shear stress develop between interacting cracks, offering a physical explanation for the formation of interconnected fracture networks, including en echelon fracture systems, under varying geometrical configurations. These findings indicate that macroscopic shear fractures may originate not only from the coalescence of tensile cracks formed during early deformation stages but also from the interaction of pre-existing cracks with different orientations, especially where tensile stress is concentrated at crack tips. The study demonstrates that the geometry of pre-existing microcracks is a primary factor controlling the spatial organization of resulting fracture networks. Fractures accommodating shear deformation, typically oriented at approximately ±30° to the axis of maximum compression, can arise from the coalescence of mode I cracks due to localized tensile stress concentration, rather than requiring shear-dominated initial conditions. This insight bridges a gap between classical fracture mechanics and observations of natural and experimental rock fracture systems, highlighting the interplay between tensile and shear mechanisms in shaping macroscopic failure patterns. Overall, our work emphasizes the importance of microstructural geometry in governing fracture evolution, offering a quantitative, framework which integrates LEFM analytical results with FEM-based models to predict the emergence of complex fracture networks from initial microcrack distributions. By linking local stress perturbations to large-scale fracture patterns, this study provides a more comprehensive understanding of the conditions leading to system-spanning fractures in the upper crust.
How to cite: Manna, L., Maino, M., Casini, L., and Dabrowski, M.: The role of pre-existing microcrack geometry in fracture initiation and propagation during elastic deformation: integrating LEFM analysis with FEM modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11582, https://doi.org/10.5194/egusphere-egu26-11582, 2026.
The Tuscan marbles, primarily exposed in the Alpi Apuane Metamorphic Complex and the Montagnola Senese ridge, record a protracted deformation history spanning the rheological spectrum from ductile flow to brittle fracturing. While the syn-metamorphic ductile evolution of these units has been extensively studied, the subsequent brittle deformation—specifically post-metamorphic faulting and fracturing—remains poorly constrained. These fracture networks are not only uplift-related features; they record a polyphase brittle history with direct implications for fluid migration, quarry slope stability, and Neogene–Quaternary stress field reconstruction.
In this work, we characterize brittle structures within marble from the Montagnola Senese, located along the Mid-Tuscan Ridge in the Northern Apennines. This marble has been quarried since Roman times, making rock mass characterization relevant for both scientific and practical purposes. We adopt a multidisciplinary approach, integrating classical field surveys with 3D digital outcrop models obtained by photogrammetry. Data were collected at the outcrop scale and subsequently extrapolated to define the fracture pattern across the entire Montagnola Senese ridge.
The detected fractures and faults cut the marble schistosity, therefore post-dating the last metamorphism event (middle Miocene). Our results reveal at least two brittle deformation phases: (I) a first, left-lateral strike-slip system, followed by (II) extensional structures, which crosscut or reuse the previous ones. Fracture attributes, such as fracture intensity and density, within the non-faulted rock mass were compared to those associated with fault damage zones. These data provide constraints on both quarrying operations and fluid circulation models, whilst contributing to the definition of the tectonic setting of this sector of the Mid-Tuscan Ridge from the middle Miocene to the present day.
How to cite: Risaliti, G., Rizzo, R. E., Tavani, S., Coli, M., Nesi, J., and Vannucchi, P.: Analysis of post-metamorphism brittle deformation in marbles: insights from Montagnola Senese, Northern Apennine, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5002, https://doi.org/10.5194/egusphere-egu26-5002, 2026.
Successful pilot projects, e.g., CarbFix (Iceland) and Wallula (USA), where CO2 has been injected into subsurface basaltic rocks, have demonstrated the potential and advantages of mafic and ultramafic rocks (unconventional reservoirs) for long-term, safe CO2 storage by mineral trapping. Despite the advantages, the CO2 storage potential in unconventional reservoirs is relatively underexplored. Consequently, the key factors (and/or their interplay) that impact secondary mineralisation and the storage capacity of basaltic lava flows in the subsurface are less well understood. In this study, we integrate field-based geological investigation with whole-rock geochemical-, mineralogical-, and SEM- analysis, to characterise Miocene age Kaldakvísl basaltic lava flows, and associated deformation structures exposed along the western and eastern coastline of the Husavík–Tjörnes Peninsula, northern Iceland. Our results reveal at least two phases of fault activities and vein development in the western coast, associated with deformation along a major normal-dextral strike-slip fault, the Husavik-Flatey Fault Zone (HFFZ), whereas the eastern coast is far less deformed. Overall, the lava flows were largely characterized by tabular, sheet-like geometry, variable thicknesses ranging from c. 1 – 7 m, and sometimes interbedded with thin volcaniclastics and paleosols. Individual lava flows exhibited large variability in intra-flow vesicle morphology, intensity, connectivity, and mineral fill that allows us to subdivide each flow sequence into three distinct units: vesicular base-, massive core-, and vesicular top- of flow. Field observations and petrological analysis of lava flow sequences from the western coast show that the flow tops have been subjected to intense and higher degrees of hydrothermal alteration and secondary mineralization (e.g., zeolites and minor carbonates) compared to the flow base and core. Conversely, lava flow sequences from the eastern coast are generally less altered, preserving the primary composition and open vesicles of the lava flows. This suggests a strong correlation between the degree of deformation and tectonic fracturing, and the degree of hydrothermal alteration and secondary mineralization, underpinning the control the former has on the latter. Furthermore, the results of XRD analysis and optical microscopy identified zeolite minerals that formed both at lower temperatures (55-110 °C), such as chabazite and heulandite, and higher temperatures (70 °C up to 300 °C), such as stilbite and analcime. We propose that these zeolite minerals form from distinct hydrothermal events, reflecting a multi-stage rather than a continuous mineralization and alteration process. Our observations suggest that the multi-stage alteration process was most likely driven by the multiple phases of fault activities and vein formation associated with the HFFZ and subsidiary faults, which provided pathways for hydrothermal fluids. This study improves our understanding of the factors that influence hydrothermal alteration and secondary mineralization in basaltic rocks and has implications for evaluating the potential role of fractures in CO2 storage in unconventional reservoirs.
How to cite: Osagiede, E. E., Brechan, C. A., Bjørnsen, T. W., Nixon, C., and Rotevatn, A.: Fracture-controlled multi-stage secondary mineralization and alteration in Kaldakvísl basaltic lava group, Husavik–Tjörnes Peninsula, northern Iceland: implications for subsurface CO2 storage via carbon mineralization, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20981, https://doi.org/10.5194/egusphere-egu26-20981, 2026.
The stiff Ypresian clays of the Kortrijk Formation occur extensively throughout the subsurface of the Princess Elizabeth Zone (PEZ), North Sea. The formation is pervasively deformed with large-scale polygonal fault networks, so-called Clay Tectonic Features (CTF; e.g. Verschuren, 2019, Marine Geology). Moreover, recently acquired samples from the Kortrijk Formation in the PEZ suggest a heavily fissured internal structure of these clays at the centimeter scale. The presence of faults and fissures in this formation have strong implications for its geotechnical properties, such as strength and stiffness, which may pose challenges for the foundations of the planned offshore wind energy farms.
With this in mind, we study the physical, mineralogical and chemical properties of the Kortrijk Formation in high-resolution using a multi-methodological approach including X-ray CT scanning, organic and inorganic geochemical analyses (LOI, organic material, calcimetry, pH, stable carbon isotopes, pXRF, XRD and ICP-OES) and sedimentological investigations (grain size, thin sections). The first samples were collected from a 20m deep borehole with alternating rotary coring and hydraulic push sampling in Rumbeke (from a section that is considered stratigraphically equivalent to the PEZ) and multiple drilling campaigns at other locations are planned.
Initial X-Ray CT scans of these samples reveal a heterogenous internal architecture containing four main feature types: bioturbation, concretions, fissures, and faults. Bioturbation occurs throughout the cores, often appearing as millimeter-thick, centimeters-long, high-density features, likely reflecting the presence of precipitated minerals such as pyrite, following microbially-mediated sulfate reduction. In contrast, concretions (siderite-fluorapatite) are rare in the core sections, consistent with their observed scattered presence in land-based observations. Fissures are recognized as low CT-density features which do not occur throughout all the core sections but are concentrated in localized zones, leaving intervening volumes of clay intact. The observed cm-scale normal faulting structures point to a local extensional regime. The geometry, pattern, and textures of the observed fissures and fractures are tested against established criteria (e.g. radial and axisymmetry, bending near the core rim, etc.) to conclusively differentiate natural features from coring-induced artifacts (Adriaens et al., 2024, Geoenergy). To quantitatively analyze all features, the X-ray CT data are processed using a comprehensive workflow involving filtering, segmentation, and grouping of features based on multi-ROI analysis using 3D connectivity. Following isolation, we perform a detailed analysis of the morphological characteristics (e.g., volume, surface area) and the three-dimensional orientation of the segmented features. The high-resolution 3D model of the features in the clay derived from CT scanning will be used to inform numerical models which will test the stiffness and long-term mechanical stability of the Kortrijk formation clays under different geotechnical loading scenarios.
By combining detailed sedimentological, mineralogical and geochemical characterization with the high-resolution CT-based structural analysis, we aim to establish the origin of the fissures and faults in the Kortrijk formation, thereby providing the geological context for their impact on geotechnical stability.
How to cite: Piret, L., Van Daele, M., Stuyts, B., De Batist, M., Dewaele, S., Kheffache, A., and Payan, M.: Cracks in our foundations: The nature and origin of fissures in the Kortrijk Formation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5516, https://doi.org/10.5194/egusphere-egu26-5516, 2026.
Exfoliation fractures are a defining feature of Yosemite’s granitic landscapes, yet the relative roles of lithology, glacial history, inherited structural fabrics, and near-surface thermal processes in controlling their geometry remain incompletely constrained. To evaluate these controls, we collected detailed field measurements across a suite of granitic domes spanning glaciated (Pothole Dome, Puppy Dome, Lembert Dome, Turtleback Dome, Olmsted Point) and non-glaciated (Half Dome, Sentinel Dome, North Dome) settings. Field investigations included systematic measurements of exfoliation sheet thickness and length, fracture orientation data, photographic documentation, and GPS surveys to assess spatial distributions of exfoliation fractures on individual domes. These data are integrated with lidar-derived topographic measurements to provide surface context and support geometry-based analyses.
Preliminary results indicate that exfoliation sheet thickness varies between domes, with glaciated domes tending to display thicker sheets and broader thickness distributions than non-glaciated domes, although substantial overlap exists between groups. Non-glaciated domes commonly exhibit thinner sheets and more variable geometries, potentially due to longer near-surface exposure and progressive weathering accumulation. Across all sites, exfoliation sheet length shows weak to moderate scaling with thickness; however, prevalent scatter in the data suggests that sheet geometry may not be influenced by thickness alone, but also by pre-existing joint sets and cross-cutting structural features that may limit lateral fracture propagation. Spatial context from GPS transects demonstrates that measurements were collected across broad surface positions on individual domes, with transects capturing tens to nearly 300 m of relief, reducing sampling bias and supporting dome-scale interpretation. Prior monitoring studies and field observations of rockfalls and active surface cracking in Yosemite suggest diurnal and seasonal thermal fluctuations contribute to ongoing subcritical crack growth, implicating thermal stresses as an active modern process superimposed onto background stresses (e.g., inherited structural features, removal of overburden, and tectonic and topographic stress). By comparing exfoliation characteristics across contrasting geomorphic settings, this study better constrains how factors such as lithology, glaciation history, inherited structures, and thermal forcing interact to shape near-surface fracture development in granitic terrains, with implications for rockfall hazard assessment and climate-sensitive rock damage processes.
How to cite: Reynolds, A. N., Stock, G. M., and Collins, B. D.: Investigating controls on exfoliation fracture geometry across glaciated and non-glaciated granitic domes, Yosemite National Park, USA, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6896, https://doi.org/10.5194/egusphere-egu26-6896, 2026.
The Einstein Telescope (ET), a proposed third-generation underground gravitational-waves observatory requires an acoustically quiet subsurface environment to minimize the effect of seismic ambient noise. A detailed site characterization is currently underway in the Euregion Meuse-Rhine (Germany, Belgium, Netherlands), one of the potential locations for the ET. The site is wedged between the northern margin of the Variscan deformation front and the subsiding Lower Rhine Graben. Subsurface fluid flow, including natural groundwater circulation and drainage constitute sources of induced seismic and gravity-gradient variations. Pre-existing faults and fractures act as preferential flow paths and, critically control potential water inflow into the infrastructure and influence related water management strategies. Consequently, characterizing the relationship between the tectonic stress field and hydraulic characteristics of the host-rock formations is essential for a resilient ET design. In this study, we investigate the evolution of the tectonic stress field (i.e., from paleo- to recent in-situ stresses) and its control on fracture permeability, using an integrated dataset of boreholes drilled in the study area from 2021 to 2025 and down to 250 to 420 m. Paleo-stress conditions are reconstructed from fracture orientations and kinematic indicators observed on drill core material and borehole-televiewer data. The present-day stress-state is evaluated using hydraulic fracturing and hydraulic testing of pre-existing fractures tests. Fracture architectures are characterized using televiewer imagery and core samples, while their hydraulic relevance is assessed through in-situ methods such as impeller flow-meter measurements, temperature logs, and hydraulic packer tests. Slip versus dilation tendency analysis is applied to evaluate deformation modes and associated permeability anisotropies. These results are compared to independent hydraulic indicators to distinguish between hydraulically active and inactive discontinuities. Our findings demonstrate how the complex tectonic history governs the present-day fracture network and associated groundwater pathways, providing key constraints on groundwater management and suitability assessments for the site selection of the ET project in naturally fractured sedimentary host-rocks.
How to cite: Burchartz, R., Kruszewski, M., Vis, G.-J., Claes, H., Müller, A., VanBrabant, Y., Deckers, J., Orban, P., Drimmer, D., Scheltens, M., Vink, B., Kiehn, M., Amann, F., and Spychala, Y.: Implications of stress field evolution on groundwater flow at the northern Variscan front and its relevance for the Einstein Telescope site selection (Euregion Meuse-Rhine), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6648, https://doi.org/10.5194/egusphere-egu26-6648, 2026.
Early fracture networks in carbonate reservoirs may constitute long-lasting fluid flow conduits and their characterisation is pivotal in reservoir modelling. These fractures are, however, often overlooked in reservoir characterisation due to a lack of predictive workflows. Yet, syn-depositional fracture networks significantly affect reservoir quality and performance due to (1) providing an early and effective fluid flow network, (2) are prone to reactivation during later tectonic events and (3) are pathways for early dolomitising fluids.
Understanding the processes of fracture formation is vital for predicting their spatial distribution. Syn-depositional fracture modelling is, however, challenging as they form without tectonic drivers, influenced instead by intrinsic stresses due to the internal geometries of carbonate platforms. Early lithification of carbonates further aids fracture formation due to internal weaknesses and rapid sediment progradation. In reef-rimmed platforms, fractures generally align perpendicular to the platform’s trajectory, while internal patterns vary without a predominant orientation.
Traditional Discrete Fracture Network (DFN) models are inadequate for predicting these networks, as fractures result from complex geometries rather than regional stress fields. Process-based stratigraphic modelling offers a powerful workflow to model carbonate internal geometries and their lithofacies zones, linking progradation/aggradation patterns to fracture intensity and spacing.
We developed a novel approach for syn-depositional fracture characterization, combining stratigraphic and fracture forward modelling to improve reservoir quality predictions and well placements. Outcrop analogue studies are used for ground-truthing and to validate the findings against digital outcrop models. This innovative workflow has the potential to significantly improve flow performance assessment for carbonate geothermal reservoirs.
How to cite: Winterleitner, G., Maerz, S., Meier, N., and Niederau, J.: Syn-depositional fracture network prediction in carbonates through process-based forward modelling., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12608, https://doi.org/10.5194/egusphere-egu26-12608, 2026.
China hosts substantial lacustrine shale-oil resources and represents a key strategic replacement for sustaining reserves growth and production. Natural fractures are critical for enhancing the flow capacity of low-porosity, low-permeability, strongly heterogeneous lacustrine shale reservoirs and also exert fundamental controls on shale-oil accumulation and preservation. In the second member of the Funing Formation (E1f2) in the Qintong Sag, Subei Basin (eastern China), fractures are abundant and diverse, yet their development characteristics remain insufficiently constrained and a systematic evaluation of controlling factors has not been fully conducted. This study integrates core-based fracture description, thin-section petrography, and borehole image logs. Fractures are classified according to geological origin, mechanical mechanism, and geometric relationships with bedding, and their development characteristics are quantitatively documented. For multiple geological attributes—including distance to faults, mechanical layer thickness, TOC, and XRD-derived mineral contents—we employ Theil–Sen estimators to conduct a “score–confidence interval” ranking of effect strength and thereby delineate the hierarchy of controlling factors.Results indicate that bedding-parallel fractures, intra-layer shear fractures, and cross-layer shear fractures are dominant, whereas intra-layer tensile fractures and bedding-parallel shear fractures are subordinate. Fractures are predominantly high-angle, with apparent fracture height on core surfaces generally <15 cm. Fracture strikes comprise multiple sets, with a dominant NNE–SSW orientation. Fractures exhibit an overall moderate degree of infilling, and calcite is the principal cement. Distance to faults is negatively correlated with structural-fracture density and is identified as the primary control, whereas mechanical layer thickness and clay-mineral content are secondary factors and also show negative correlations with structural-fracture density. In contrast, higher TOC and greater lamination density promote the development of bedding-parallel fractures and constitute the primary controls, whereas higher clay-mineral content and greater mechanical layer thickness act as secondary factors that are unfavorable for bedding-parallel fracture development. These results clarify fracture distribution patterns in E1f2 and provide geological constraints for shale-oil exploration and development in eastern China, while also offering a transferable framework for the quantitative evaluation and ranking of fracture-controlling factors.
How to cite: Li, S., Lyu, W., Zeng, L., Shen, B., Ma, X., and Li, P.: Development characteristics and controlling factors of natural fractures in lacustrine shale oil reservoirs: A case study of the second member of the Funing Formation (E1f2), Qintong Sag, Subei Basin, eastern China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15124, https://doi.org/10.5194/egusphere-egu26-15124, 2026.
Rockfalls are among the most critical phenomena in geomechanics due to the significant risk they pose to human lives and infrastructure. Rockfall risk is defined by the interplay between hazard and the potential impact on exposed elements. Specifically, hazard assessment relies on the propensity for detachment (estimated frequency), event magnitude (volume), and intensity (kinetic energy).
Detachment propensity is governed by predisposing structural conditions and analyzed by the probability of failure modes, such as planar sliding, wedge sliding, or toppling, in relation to the main discontinuity sets. Conversely, magnitude and intensity depend on the probable volume of the unstable block and its potential propagation path.
Traditional geo-structural surveys, based on direct acquisition using standard instruments (e.g., geological compass and measuring tape), characterize, among other parameters, discontinuities in terms of orientation (dip angle/dip direction), spacing, and persistence. While the orientation of discontinuities, combined with mechanical properties, allows for the evaluation of the propensity to detachment, the definition of spacing and persistence is crucial for estimating block volume. However, this deterministic approach is often difficult to generalize to an entire slope, making accurate volume definition a persistent challenge.
To address this limitation and avoid the risks associated with direct data acquisition in hazardous areas, indirect remote sensing approaches have gained prominence. This study addresses the rockfall hazard characterization of a critical slope in the Palermo Mountain System (Sicily, southern Italy), where frequent rockfalls have disrupted vehicular traffic. Utilizing a Terrestrial Laser Scanner (TLS), the authors applied an indirect characterization method. Multitemporal acquisitions enabled a high-resolution 3D Point Cloud-based analysis, allowing for a more accurate and safe definition of hazard parameters in this complex environment.
How to cite: Mineo, G., Rosone, M., Martinello, C., Mercurio, C., Rotigliano, E., and Cappadonia, C.: Indirect Rock Mass Characterization Using High-Resolution 3D Point Clouds Applied in Hazardous Rock Slopes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18351, https://doi.org/10.5194/egusphere-egu26-18351, 2026.
Strike-slip fault zones often play a key role in controlling brittle deformation patterns in fold-and-thrust belts. Yet, the distribution of associated fractures and their interactions with fold-related structures remain insufficiently understood across scales and as part of the deformation history. In the Jura Mountains, previous work in the Central Internal Jura, notably at Creux-du-Van, proposed a multi-scale hierarchy of strike-slip faults and associated fracture networks based on sub-seismic structures spanning meter- to kilometer-scale. This study extends the multi-scale structural analysis to a regionally mappable ~12 km long N–S striking sinistral fault zone, the Suchet Fault. The fault is exposed along the E–W-oriented Gorges de l’Orbe, where incision into Upper Malm limestones enables largely continuous outcrop-scale access to fault-related damage zones.
To address the multi-scale character of this system, we combine field-based structural mapping at 1:5,000 scale and three-dimensional structural interpretation of publicly available aerial LiDAR data (SwissALTI3D) with systematic fracture data acquisition along four scanlines totaling 157 m. Scanlines are positioned at varying distances from the fault core, defined by the presence of fault breccia and gouge lenses, and across western and eastern structural compartments, spanning fault-proximal to fault-distal domains. This configuration enables comparison between fracture populations associated with fault-zone architecture and those interpreted as fold-related or background fracturing.
The Suchet Fault separates two contrasting structural domains. The western compartment is characterized by NW–SE striking fold trains, whereas the eastern compartment exhibits a comparatively flatter structural geometry. Within the vicinity of the fault trace, bedding orientations rotate progressively toward the N–S fault trend, with gentle eastward dips (~15°). Locally, near the fault core, bedding dips steepen and may reach up to 70°, indicating increased strain localization within the damage zone. LiDAR-based structural interpretation identifies three dominant fracture populations, with the NW–SE striking set displaying comparatively longer fractures than the N–S and NE–SW sets.
Fault-slip indicators show dominant subvertical conjugate strike-slip pairs at outcrop scale, comprising sinistral N–S to NNE-SSW striking faults and dextral NW–SE striking faults. Preliminary paleostress inversion analysis indicates a strike-slip regime characterized by a subhorizontal NW-directed maximum principal stress and a subvertical intermediate stress, consistent with results from other sectors of the Central Internal Jura. Fracture density (P10) increases toward the fault core, with values close to the brecciated core notably higher than those measured beyond 100 m.
This study emphasizes the need for robust fracture set definition and sequencing as a basis for structural analysis, including paleostress orientations and spatial variations in fracture intensity and anisotropy. This study evaluates whether structural patterns and paleostress behaviors identified at Creux-du-Van are comparable to those observed in the Gorges de l’Orbe area, at the scale of larger strike-slip fault zones. It also considers the potential regional implications of these structural features for fracture-controlled fluid flow in the Jura Mountains and potentially downstream, in the geothermal reservoirs beneath the Molasse Basin.
How to cite: Caldeira, J., Samsu, A., Tanaka, A., and Bazalgette, L.: Strike-slip fault zone architecture in folded Upper Malm limestones at Gorges de l’Orbe, Central Internal Jura, Switzerland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14987, https://doi.org/10.5194/egusphere-egu26-14987, 2026.
A NE-SW fault system described in the eastern sector of the Trans-Mexican Volcanic Belt (TMVB) has been active since the Pliocene and continued up to the Holocene with dip-slip kinematics. In a broad view, these NE-SW faults can be correlated to the Tenochtitlan fault system that extends from the southwest coast of Mexico to central Mexico, into the TMVB. The length of the faults, the damage zone width, and more than one slickensides on the fault planes suggests a complex deformation history. In this study, we investigate the geometry and kinematics of the NE-SW faults in the Miocene-Pleistocene rocks in the eastern sector of the TMVB to determine the kinematics of these faults during the Late Miocene to Holocene, for which it is unknown. Our results suggest that the Miocene rocks record two deformation events, one of which is related to crustal shortening that produced a strike-slip activity in the NE-SW faults during the Late Miocene. The second one is associated with crustal extension and the activity of the NE-SW faults with dip-slip kinematics. This extensional event was active during the Pliocene-Holocene. The reactivation analysis and our field observations suggest that the NE-SW normal faults are related to the reactivation of previous NE-SW strike-slip faults. The change in the kinematics of the NE-SW faults explains the complex geometry of the damage zones of the kilometric NE-SW faults and the highly fractured Miocene rocks.
Based on the fault system orientation, it is clear that these faults are incompatible with the field stress recorded in the eastern sector of the TMVB. This fact suggests that the NE-SW fault system is probably related to reactivated basement structures within a three-dimensional deformation with a complex deformation history. The activity type of the NE-SW faults is probably related to the dynamics of the subduction process in the southwest of Mexico, associated with the change in the dip (decrease) and the convergence velocity of the Cocos plate.
How to cite: Vasquez Serrano, A., Rangel Granados, E., and Arce Saldaña, J. L.: NE-SW fault system in the eastern sector of the Trans-Mexican Volcanic Belt: Origin, deformation, and reactivation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13737, https://doi.org/10.5194/egusphere-egu26-13737, 2026.
Fault damage zones are regions surrounding a fault core where secondary fractures are intensely developed due to distributed deformation. Previous studies on small-scale faults (consisting of one or two geometric segments) have predicted that the characteristics of the damage zone vary depending on the position along the fault. However, applying these models to large-scale fault zones is challenging due to the lack of continuous exposure and their inherent structural complexity.
This study aims to analyze the spatial variability of damage zone width in relation to fault geometry, focusing on medium-scale strike-slip faults (comprising three or more geometric segments), which offer a balance between structural complexity and observable continuity. The study area, Geoje Island, consists of hornfelsic Cretaceous lacustrine sedimentary rocks. The extensive wave-cut platforms along the coast provide excellent exposure for characterizing the geometry of the master fault and associated damage zones.
Fracture density (P21) was systematically quantified across fault segments and boundaries using circular scanlines arranged along strike-perpendicular traverses. The width of the damage zone along each traverse scanlines was determined by analyzing the changes in fracture density relative to the distance from the Principal Displacement Zone (PDZ). The results indicate that the width of the damage zone is highly variable and exhibits significant asymmetry in certain sections. Specifically, in linking damage zones, a widespread distribution of damage is observed beyond the extensional overlap zones, contrasting with patterns typically seen in small-scale faults. Furthermore, strong asymmetry is prominent in regions where the fault strike changes. However, such widespread damage distribution and asymmetry are well consistent with the characteristics of tip damage zones observed in small-scale faults.
These observations indicate that geometric complexity at these locations contributed to arresting rupture propagation during reactivation. Although individual rupture mechanics are similar across scales, the cumulative effect of geometric barriers in medium-scale faults appears to dictate the spatial evolution of the damage zone. These findings are expected to provide valuable insights for predicting and understanding the architectural evolution of large-scale fault zones.
This research was supported by a grant (2022-MOIS62-001(RS-2022-ND640011)) of National Disaster Risk Analysis and Management Technology in Earthquake funded by Ministry of Interior and Safety (MOIS, Korea).
How to cite: So, J., Seo, Y., Park, K., Bae, S., and Kim, Y.-S.: Variability of Fault Damage Zone Width in Strike−Slip Faults: A Case Study from the Coast of Geoje Island, Korea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12013, https://doi.org/10.5194/egusphere-egu26-12013, 2026.
Along the downfaulted axial zone of the southern Apennines fold-and-thrust belt of Italy, ongoing work focuses on field survey of high-angle extensional fault zones, and integrated microstructural, mineralogical, and stable isotope analyses of fault-related calcite veins. Two study areas are investigated. The first one lies in the southern portion of the seismically active Irpinia region, the second one along the southern flanks of the Raparo Mt., Basilicata. There, we study Mesozoic shallow-water carbonates that first underwent thrusting tectonics, and then extension and exhumation from shallow crustal depths. Within the fault zones, we select the high-angle Slip Parallel veins (SP-veins) and low-angle Comb veins (C-veins), respectively oriented parallel and perpendicular to the fault dip.
In the Irpinia region, results of microstructural analysis of the vein assemblage indicate that the high-angle faults are characterized by veins containing blocky to elongated and fibrous calcite. Blocky calcite minerals show type I and II twinning. Furthermore, inclusion bands associated with crack-and-seal processes are also present. In line with established microstructural interpretations, blocky calcite is interpreted as post-kinematics, whereas elongated and fibrous calcite is regarded as syn-kinematics. Occurrence of type I and II calcite twinning suggests that the intracrystalline deformation temperatures in these regions falls within ca. 150o C - 300o C.
At the Raparo Mt., microstructural data are consistent with blocky, elongate-blocky calcite textures of both SP- and C-veins. The former veins are dominated by blocky calcite with established presence of Type I and II calcite twinning, while the latter veins occasionally show blocky calcite. This area also shows widespread occurrence of both high- and low-angle veins with microcrystalline textures, which suggest that rapid cooling of the mineralizing fluids and precipitation took place in their formation process. Common tar-rich mineralization is also observed along the low-angle veins.
Aiming at deciphering the relative timing of formation and paleo stress regimes, present work is dedicated to the detailed microscale documentation of the crosscutting/abutting relations among the different vein sets. At the same time, extraction of powder samples is taking place for subsequent geochemical analyses. Results will be key to determine the source/s of the mineralizing fluids, determination of isotopic fractionation, and amount of fluid-rock interaction. These analyses will enable formulation of valuable hypotheses regarding the modalities of ingression of the mineralizing fault fluids within the study fault zones.
How to cite: Kyari, A., Zummo, F., Abdallah, I., Paternoster, M., Caracausi, A., and Agosta, F.: Integrated field and laboratory analyses of vein assemblages from the downfaulted southern Apennines fold-and-thrust belt, Italy., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4297, https://doi.org/10.5194/egusphere-egu26-4297, 2026.
Posters virtual: Wed, 6 May, 14:00–18:00 | vPoster spot 1a
EGU26-16222 | ECS | Posters virtual | VPS30
Quantitative lineament network analysis of a folded crystalline terrain using FracPaQ: The Kadavur Anorthosite Complex, Southern Granulite TerraneWed, 06 May, 14:03–14:06 (CEST) vPoster spot 1a
The Kadavur Anorthosite Complex represents a distinctive structural domain within a folded high-grade crystalline terrain, where a massif-type anorthosite body occupies the core of a regional-scale fold and is surrounded by folded quartzite ridges. This study examines the relationship between lineament development and the pre-existing ductile fold architecture through integrated DEM–SRTM data analysis and quantitative lineament network characterisation using FracPaQ. The objective is to assess how fold geometry and lithological contrasts influence the spatial distribution and mechanical behaviour of brittle structures. DEM analysis reveals a coherent folded morpho-structural architecture characterised by a well-defined core, axial-plane domains, and limbs expressed as quartzite ridges. FracPaQ-derived results show that lineaments are non-randomly distributed and define multiple dominant orientation sets, reflecting systematic structural control rather than random patterns. Spatial variations in lineament density and lineament intensity show pronounced localisation within and adjacent to the fold core, whereas lineament attributes vary systematically between the anorthosite-dominated core and the surrounding folded quartzite limbs.
Slip tendency analysis indicates that brittle deformation is predominantly shear-controlled across the study area, while dilation tendency values are generally low to moderate, suggesting a subordinate role for opening-mode fracturing. Lineaments within the anorthosite core are comparatively longer, less densely spaced, and display lower orientation dispersion, reflecting brittle stress accommodation within a mechanically competent lithology. In contrast, lineaments developed in the folded quartzite ridges are shorter, more closely spaced, and strongly influenced by lithological layering and fold-related bending stresses.
Although comparable lineament orientation patterns occur across the fold core, axial planes, and limbs, their geometric characteristics, spatial distribution, and inferred mechanical roles differ significantly, indicating that brittle deformation was modulated by local fold geometry and lithological contrasts. The results indicate a structural association between ductile folding and later brittle deformation; however, the tectonic conditions responsible for anorthosite exhumation cannot be uniquely constrained from the present dataset. This study highlights the importance of domain-specific lineament analysis in folded crystalline terrains and emphasizes the role of inherited ductile architecture in controlling later brittle deformation.
How to cite: Prathapachandran, A., Manilal Girija, A., and Kumar, R. S.: Quantitative lineament network analysis of a folded crystalline terrain using FracPaQ: The Kadavur Anorthosite Complex, Southern Granulite Terrane, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16222, https://doi.org/10.5194/egusphere-egu26-16222, 2026.
EGU26-18367 | ECS | Posters virtual | VPS30
Quantitative Characterization of Fracture Networks Based on Geometric-Topological Integration and Its Application in Hydrocarbon Migration Prediction in the Western Junggar BasinWed, 06 May, 14:06–14:09 (CEST) vPoster spot 1a
With the continuous advancement of geological research, quantitative analysis of fracture networks has become a crucial research direction in geological exploration and resource development. To overcome the limitations of traditional methods in quantitatively analyzing fault data under complex geological conditions, we adopt a quantitative fracture characterization method based on geometric and topological theories. This study focuses on the overlay analysis of multi-period and multi-layer faults in a typical area of the western Junggar Basin, aiming to reveal their significant role in hydrocarbon exploration. By means of this method, we achieve multi-dimensional automatic quantification of geometric features (including fracture network length, orientation, and Pxy system), as well as node/branch types and topological parameters. Through the construction of a fracture topological network, we can quantitatively analyze the connectivity characteristics of each period and the vertically favorable conduction zones across multiple periods, thereby providing valuable guidance for hydrocarbon migration path prediction.
How to cite: Tao, Y., Cui, L., Niu, Y., Huang, Y., Bai, S., Zhao, G., Piluolan, P., and liu, Y.: Quantitative Characterization of Fracture Networks Based on Geometric-Topological Integration and Its Application in Hydrocarbon Migration Prediction in the Western Junggar Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18367, https://doi.org/10.5194/egusphere-egu26-18367, 2026.
EGU26-18303 | Posters virtual | VPS30
Anisotropy of fracture nodes using wavelet analysisWed, 06 May, 14:30–14:33 (CEST) vPoster spot 1a
Abstract:
Fracture networks play a critical role in controlling rock mechanics, fluid flow, and crustal deformation. However, many conventional analytical approaches do not adequately account for the spatial anisotropy of fracture nodes. This study introduces a wavelet-based angular variance method to quantify multiscale anisotropy in fracture network nodes, including I-, Y-, X-, and X + Y-nodes, as well as barycenters, using both synthetic and natural datasets.
Synthetic experiments demonstrate that isotropic fracture systems produce spatially random node distributions, whereas anisotropic systems generate distinct directional clustering, such as cross-shaped patterns aligned along NE–SW and NW–SE orientations. Application of the method to field data reveals strong correspondence between node anisotropy and underlying structural features. In the Jabal Akhdar dataset, X- and X + Y-nodes show pronounced elongation along an ENE–WSW direction, I-nodes exhibit weaker lobation in the same orientation, and barycenters remain largely isotropic. In contrast, the Getaberget dataset displays significant anisotropy across barycenters and multiple node types (Y, X, and X + Y), with dominant N–S to NNW trends consistent with NE–SW and NW–SE fracture sets.
These results demonstrate that wavelet-based node analysis is capable of detecting subtle, scale-dependent anisotropy in fracture systems. The proposed approach provides a sensitive, continuous, and scalable framework for quantifying fracture network organization, offering valuable insights for reservoir characterization, geothermal resource assessment, and the analysis of fracture-controlled fluid flow in geological systems.
Keywords: Fracture network; Nodes; Spatial analysis; Point anisotropy; Wavelet analysis
Acknowledgement
PG acknowledges the Indian Institute of Technology Roorkee and the Ministry of Human Resource Development (MHRD), Government of India, for support through a PhD fellowship. SB acknowledges financial support from the Department of Science and Technology (DST), Government of India (Project No: SRG/2021/001903), and from FIG (Grant No: FIG-100886-ESD), Indian Institute of Technology Roorkee, India.
How to cite: Gairola, P. and Bhatt, S.: Anisotropy of fracture nodes using wavelet analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18303, https://doi.org/10.5194/egusphere-egu26-18303, 2026.
