Fluids within low-porosity rocks are transported through networks of interconnected microcracks and fractures. Under crustal conditions, rocks are subjected to true triaxial stress states characterized by three unequal principal stresses, where σ1>σ2>σ3. These triaxial stress states can influence the magnitude and direction of fluid flow in two ways. First, cracks may open, close, and/or slip depending on their orientation with respect to the anisotropic stress field, and thereby potentially reducing fluid flow in certain directions while enhancing flow in others. Second, once the magnitude of differential stresses surpasses the onset of dilatancy in the rock, new cracks form, providing additional pathways for fluid transport. The geometry of these new fractures, and therefore the direction of fluid flow enhancement, is also controlled by the anisotropic stress field.
Despite the fundamental role of triaxial stresses in controlling the magnitude and direction of fluid flow through the crust, very little is known regarding the anisotropy of permeability under true triaxial stress states. This knowledge gap exists primarily because experimental permeability measurements are typically conducted under axisymmetric stress states (σ1>σ2=σ3) with fluid flow and permeability usually measured only parallel to the σ1-direction. To address this, we have developed a new True Triaxial Apparatus (TTA) at UCL equipped with a pore fluid system to deform cubic, saturated rock samples under true triaxial loading while contemporaneously measuring permeability along all three loading axes and recording the output of acoustic emissions (AEs).
Results from tests conducted on 50 mm cubes of initially isotropic Etna basalt under true triaxial loading indicate that, under relatively low differential stresses (σ1-σ3<180 MPa), fluid flow is reduced by over one order of magnitude in the direction parallel to σ1. Increasing the magnitude of stress along the σ2 axis also results in a decrease in permeability along the same axis. The increase of differential stress eventually leads to an increase in AE hits, which further coincides with a sudden increase in permeability along the σ2-axis. Our results revealed two completely different anisotropic permeability behaviours during the progressive deformation of the rock. At lower differential stresses, permeability is stress-controlled and is characterised by the reduction of permeability parallel to σ1. Increasing differential stresses beyond the onset of dilatancy in the rock results in the creation of new cracks that creates pathways for fluids parallel to the σ2 axis. Further experiments and analysis are in progress to fully quantify and characterise these behaviours.
How to cite: Stanton-Yonge, A., Mitchell, T., Meredith, P., Healy, D., Browning, J., and Adamus, F.: Stress versus damage-induced permeability anisotropy under true triaxial stress states in Etna Basalt , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3325, https://doi.org/10.5194/egusphere-egu25-3325, 2025.
Understanding the damage processes in clay-bearing rocks is a decisive factor in geological engineering. But, more generally, they may also contribute to localized deformation and thus the rupture of fault gauges in seismic zones. Due to their physical and mechanical properties, such as low permeability, fracture healing potential, and effective radioactive elements adsorption capacity, several European countries plan to use these impermeable rocks to confine their nuclear waste in deep geological repositories. However, structural damage could lead to uncontrolled radionuclide dispersion by advective transport, thus the early detection of the damaging nucleation and evolution is decisive in geological engineering.
This study aims to explore the interplay between P-wave ultrasonic velocity and the micro-deformation mechanism identified by digital image correlation (DIC) in order to predict the failure of the sample.
To this end, uniaxial compression tests are performed on small-scale Tournemire shale samples (8 mm in width and twice as long) using a home-designed miniature loading frame under controlled relative humidity of RH = 75% and RH = 20%. These tests involve two simultaneous measurements: 1) the axial and lateral P-wave travel times, recorded by an active emission system, and 2) the full displacement field on the sample surface, based on Digital Image Correlation (DIC) applied to high-resolution optical or Environmental Scanning Electron Microscopy (ESEM) images. The latter allows for the calculation of 2D full strain fields in order to characterize the deformation at different scales while performing simultaneous acoustic measurements. The processed images are representative of two distinct scales: one at the microscale using the ESEM with a resolution of 24 nm/pixel and the other at the mesoscale using an optical camera with a resolution of 0.55 μm/pixel.
The results allow us to discuss the global evolution of the acoustic wave velocities during the uniaxial loading process with respect to the identified active micro-damage mechanisms.
How to cite: Lusseyran, M., Bonnelye, A., Dimanov, A., Fortin, J., Tanguy, A., Gharbi, H., and Dick, P.: Prediction of clay-rich rock failure coupling local and global non-destructive measurement techniques., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13049, https://doi.org/10.5194/egusphere-egu25-13049, 2025.
Frictional strength of a fault surface is controlled by the yield strength of microscopic asperities. During any quasi-stationary contact, these asperities transiently creep to a characteristic nm-to-μm length scale to achieve a steady-state strain-rate, which governs the “state” evolution of the fault interface. In the Low-Temperature Plasticity regime, asperities predominantly deform through dislocation creep which is controlled by the dislocation density at the junction. While the density of the statistically stored dislocations (ρSSD) controls the steady-state deformation of the asperities, density of the geometrically necessary dislocations (ρGND) governs the transient creep.
We have designed a novel nanoindentation based cyclic deformation experiment to assess the evolution of dislocation densities at asperity contact with progressive hardening. Experiments with normal load ranging from 1 to 8 mN and 10 continuous deformation cycles conducted on single crystals of San Carlos Olivine reveal that with increasing iteration of deformation cycle, and thus strain-hardening, Yield Stress and the percentage of anelastic recovery increases nonlinearly. We show that progressive hardening increases the ρGND at asperity contact that alters the root-mean-square curvature of the asperity, while a similar increment in the ρSSD reduces the characteristic length scale of deformation and increases the macroscopic strength of the material. These observations further validates that the “contact quality” controls the “contact quantity” of nanoscale asperities. Integrating the experimental observations with the existing theories on scale-dependent strength of asperities and nanoscale surface roughness, we have developed a semi-analytical model that relates coefficient of friction with the characteristic length scale of asperity deformation, dislocation densities and roughness parameters. Our model predicts that increasing strain-hardening can reduce the frictional aging for a given amount of fault-normal strain, which provides a microphysical basis for understanding the rate-and-state based friction laws of natural fault surfaces. This study provides a novel mechanistic interpretation of the frictional evolution of nanoscopic self-affine rough surfaces and has potential applications in understanding the transient deformation of the lithospheric mantle.
How to cite: Mukherjee, R. and Misra, S.: Role of Strain Hardening in Frictional Aging of Nanoscale Asperity Contacts , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-912, https://doi.org/10.5194/egusphere-egu25-912, 2025.
Fractures in rocks are ubiquitous, from grain-scale microcracks to crustal scale faults. Importantly, fracture networks allow crystalline rocks to store and transport fluids, which can then interact with rock-forming minerals and enhance rock deformation processes, leading to slow, progressive fracture growth that is time-, stress- and environment-dependent.
We previously reported progressive changes in physical and mechanical properties of granitoid boulders exposed at the surface from zero to around 100 ka in Eastern California, USA. We noted systematic decreases in tensile strength, uniaxial compressive strength, elastic modulus and seismic wave velocities, and systematic increases in porosity and permeability, with increasing surface exposure age. We postulated that the observed changes were likely functions of an increase in the level of crack damage over time. Hence, we interpreted the changes as reflecting progressive subcritical crack growth arising from ubiquitous, but relatively low magnitude environmental stresses acting continuously on the boulders over the extensive periods of exposure.
Here, to avoid ambiguity in interpretation, we report direct measurements of key fracture mechanical properties made on samples from the same boulders. The critical stress intensity factor for dynamic fracture propagation (fracture toughness, KIC) was measured using the Double Torsion testing methodology. We also measured the pre-exponential offset (A) and the subcritical crack growth index (n) in the Charles’ Law relation: V = A (KI/KIC)n, using the same technique (where V is the crack growth rate). We find that KIC decreases from around 2.0 MPa.m-1/2 in fresh material to around 0.5 MPa.m-1/2 in boulders exposed for around 90 ka, and that the A offset increases from -5 to +20. By contrast, we find no significant change in the n index, which has a value of around 60 ± 10, apparently regardless of exposure age.
These results suggest that the ease of nucleation and rate of growth of new cracks increases with exposure age, consistent with rocks weakening over time through decreasing strength. However, this is in direct contradiction with extensive field measurements that appear to show that the rate of crack growth (measured by crack intensity on thousands of rocks) decreases over time.
So, how do we reconcile these apparently contradictory observations? Here we observe that over exposure time, individual cracks can nucleate and then continue to grow under low imposed stress. However, this assumes that the stress reaching the crack tip does not change over time. But, in nature, the stress intensity (KI) felt at the crack tip is a function of the stress propagating throughout the rock mass. As the bulk rock becomes more compliant (lower Young’s modulus) over exposure time, due to diffuse microcracking, the rock accommodates more elastic strain and translates a lower net stress intensity to each individual crack tip. Thus, we expect the overall rate of cracking in any rock mass to depend on the instantaneous ratio between the decreasing stress intensity factor and the decreasing fracture toughness (i.e., KI/KIC).
How to cite: Meredith, P., Nara, Y., Eppes, M.-C., Rasmussen, M., Keanini, R., Mushkin, A., and Mitchell, T.: Progressive changes in rock fracture mechanical properties with exposure age at the Earth's surface., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3556, https://doi.org/10.5194/egusphere-egu25-3556, 2025.
Wildfires are an increasing global concern due to their profound impact on the environment and human life. These events affect a wide range of environments, from arid regions and forests to other highly flammable areas, such as the Bohemian Switzerland National Park in the Czech Republic. In 2022, a large-scale wildfire in this region—characterized by its sandstone rock formations near the Czech-German border—highlighted the importance of understanding the effects of extreme temperatures on rock properties. While wildfires occur almost annually in this region, the unprecedented scale of this event may have been exacerbated by factors such as wind and prolonged hot climate conditions influenced by ongoing climate change.
To investigate the impact of high temperatures on rock properties, we collected rock samples representing all major lithologies across Czechia, including sandstone and crystalline rocks. After preparing the samples, we exposed them to a controlled heating process, mimicking wildfire conditions. Samples were first dried at 105°C and then incrementally heated to 200°C, 400°C, 600°C, and 800°C, with ultrasonic P- and S-wave testing performed after each temperature stage to assess their dynamic elastic properties. The heating process was carefully designed to replicate natural wildfire conditions, including gradual temperature increases, targeted temperature suspension, and subsequent cooling.
Our findings reveal distinct thermal responses in rock properties. Sandstone and crystalline samples initially strengthened after heating to 200°C, likely due to changes in cementation. Beyond this point, progressive weakening occurred, with rocks reaching their weakest state at 800°C. These results align with previous studies, offering valuable insights into the thermal behavior of rock materials under wildfire conditions and contributing to a broader understanding of the environmental impacts of high-temperature events.
How to cite: Rastjoo, G., Blahut, J., Racek, O., Nguyen, X. X., and loche, M.: Assessing the Impact of Wildfires and High Temperature on Rock Properties on Diverse Lithologies in the Czech Republic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6366, https://doi.org/10.5194/egusphere-egu25-6366, 2025.
Volcanic eruptions are often preceded by intense deformation and volcano-tectonic microearthquakes, which evidence the progressive failure of the volcanic edifice. Studying this process may be of interest for the more general understanding of the progressive failure of rocks.
Active volcanoes are pressurized by fluids and undergo considerable deformation prior to eruption. Surface deformation and seismicity are recorded continuously by volcanological observatory networks; both are due to the action of fluid pressure and rock weakening with deformation, and can be used to quantify fluid pressure variations and rock damage. In this talk we will show how coupling a simple fluid pressurization model with a seismicity-based damage model can be used to explain the surface deformations recorded on basaltic volcanoes. In particular, we will describe the foundations of the damage model. We'll show how damage, crack interaction and stress diffusion can explain the inverse Omori law often evidenced before eruptions, and the relationship between this law and entropy production during progressive rock failure. Finally, using a dataset from 24 pre-eruptive periods at Piton de la Fournaise, we’ll show how these concepts can be used to track the temporal evolution of the state variables that can help describe pre-eruptive processes.
How to cite: Got, J.-L., Peltier, A., and Marsan, D.: What can we learn from progressive rock failure in volcanoes?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12123, https://doi.org/10.5194/egusphere-egu25-12123, 2025.
Thermal weathering has a long-term (decadal to millenia) effect on the physical and mechanical properties of rocks and can directly influence rockfall hazard. However, despite substantial research, the processes of rock degredation from thermal influences are not completely understood. This study analyzed data from two, 3-meter-deep boreholes spaced approximately 1.8 km apart in western Yosemite Valley, California (USA) subject to different thermal regimes. The boreholes were drilled horizontally into lithologically and macroscopically identical rock (El Capitan Granite) with no visible fractures. However, we located the two boreholes with different aspects, one on a sun-facing cliff with southern aspect, and one on a sun-shaded cliff with northern aspect. Sensors in the boreholes monitor temperature changes at 10-minute intervals and were installed from the surface to 3-m-depth at increasing increment intervals (i.e., at the surface, 5, 10, 20, 30, 50, 75, 100, 150, 200 and 300 cm). A comparison of the temperature data showed significant differences in rock surface temperatures and temperature gradients between the south- and north-facing cliffs. Between April and November 2024, the south-facing site showed a greater surface temperature range (51.2°C) and average (28.3°C) than the north-facing site (28.3°C range and 17.3°C average). At 3-m-depth, the south-facing site had a temperature range of 10.6°C (21.0°C average) compared to a 8.1°C range (13.1°C average) for the north-facing site. We also analyzed the borehole cores using applied ultrasonic P- and S-waves to calculate their dynamic elastic properties. Despite similar lithology and structure, significant differences were found between the sites. Samples from the south-facing slope, which receives more thermal energy given its location in the Northern Hemisphere, proved to be more weathered, coincident with rock of higher porosity and lower dynamic moduli. In contrast, rock samples from the north-facing and consequently wetter slope showed lower porosity, higher elastic moduli, and a more pronounced gradient of weathering towards the surface. We hypothesize that diurnal and annual thermal stress changes play a larger role in rock weathering than previously assumed, possibly exceeding the long-term influence of other factors, such as groundwater. However, further measurements of rock properties at multiple locations are required to confirm this hypothesis.
How to cite: Blahůt, J., Stock, G. M., Collins, B. D., Rastjoo, G., and Racek, O.: Investigating the effects of thermal weathering on bedrock cliffs using in-situ borehole monitoring in Yosemite Valley, California, USA, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2916, https://doi.org/10.5194/egusphere-egu25-2916, 2025.
Sea-wave impacts and near-surface thermal fluctuations are periodic stressors capable of exerting long-term mechanical effects that drive progressive rock mass failure and are regarded as a preparatory process for landslides. These processes pose significant hazards in coastal areas, which are expected to increase due to climate change. Despite scientific consensus identifying sea waves as a causative factor for slope instability, the mechanisms that govern subcritical crack growth and the transition to critical failures remain poorly understood. Failures often occur without any precursory signs and may happen even in the absence of major destabilizing forces.
To investigate the fatigue processes experienced by rock masses under periodic loading and to understand the mechanisms driving coastal cliff failure with a goal in hazard assessment, a coastal sector was instrumented, monitoring both subaerial and underwater environments. This monitoring focuses on the effects of stressors and corresponding rock mass deformations. As part of the TRIQUETRA Horizon EU project, the Ventotene Field Laboratory (VFL) was established and inaugurated in May 2024. The VFL was located in a portion of the tuffaceous sea cliff of the Punta Eolo promontory, where a thick succession of ignimbrite deposits (ascribable to the Parata Grande geological unit) experienced large instabilities in the past tens of years. The cliff is still evolving with rockfall and rock toppling mechanisms, that are threatening the archaeological excavation of the Roman Villa of Giulia (of the 1st century A.D.) and the Cemetery where Altiero Spinelli, the father of European thought, lies.
The monitoring system includes a fully equipped weather station, conventional geotechnical sensors, and specialized devices for measuring sea-wave characteristics. These devices include a sea-wave and currents Doppler profiler, dynamic titanium water-tight pressure gauges to assess wave impacts at the cliff base, and instruments to measure elastic and plastic deformation of the fractured rock mass, such as crack meters, a biaxial tiltmeter, thermocouples, and load cells.
Additionally, laboratory mechanical investigations were carried out to evaluate the strength and stiffness of the intact rock while examining the roles of water saturation and salt crystallization in rock weathering.
Findings from the first year of monitoring revealed notable responses of the fractured rock mass to intense rainfall events, which caused sharp and partially reversible fracture openings. Cyclical deformation, including dilation and block tilting, was observed in response to daily and seasonal temperature fluctuations. Data collected from the monitoring system have been used to inform a stress-strain finite difference numerical model to analyse the static influence of basal notches on slope predisposition, as well as the preparatory effects on slope stability of combined thermal and marine actions. Ongoing numerical and laboratory geomechanical analyses aim to provide a more comprehensive understanding of the progressive rock failure processes driving the evolution of these complex systems.
How to cite: Marmoni, G. M., Feliziani, F., Grechi, G., Montagnese, M., Bozzano, F., and Martino, S.: Progressive rock failure in coastal cliffs: analysis of preparatory and triggering actions in a field laboratory at the Island of Ventotene (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16797, https://doi.org/10.5194/egusphere-egu25-16797, 2025.
The Universal Distinct Element Code (UDEC) based on Discrete Element Method (DEM) has gained widespread prevalence in simulating multiscale rock failure in varied branches of geotechnics. Simulation performance demonstrates a heavy reliance on modelling parameters. The trial-and-error approach and parametric sensitivity analysis have long been the primary method employed in the parametric calibration in UDEC. However, they share the drawbacks of excessive computational resources, high dependence on human subjectivity, and the challenge of handling high-dimensional and nonlinear complex parameter spaces. To address this issue, we employed artificial intelligence (AI) to handle multidimensional data and higher-order nonlinear relationships between modelling parameters and macroscopic responses of numerical models. A wide range of preset gradient-based modelling database was established to pre-train the machine learning model to map the parametric relationships. Then, this pre-trained model was combined with an experimental database with various lithologies to conduct an inverse search of the input parameters in UDEC. To further improve the estimates, a gradient-based hyperparameter optimisation, implemented via GridSearch, was applied to identify the optimal parameter set by minimising the loss function. The calculated modelling parameters were subsequently input into UDEC for simulation and validation. Hundreds of comparisons reveal that the simulated results by UDEC align closely with those from the experimental database, demonstrating the feasibility of our model. This research provides a substantive solution to the parametric calibration in UDEC, significantly improving both the reliability and convenience of UDEC simulations.
How to cite: Bu, F., Lin, R., Jaboyedoff, M., Derron, M.-H., Liu, W., and Xue, L.: AI calibration of modelling parameters in UDEC, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12136, https://doi.org/10.5194/egusphere-egu25-12136, 2025.
Heterogeneous porous structures, spanning multiple length scales from nano- to macro-levels, are found in both natural and engineered materials. To fully understand their mechanical and fracture behaviors, it is essential to explore the relationship between porosity and mechanical integrity at different scales. In this presentation, we focus on the mechanical responses of these complex structures, with a particular emphasis on the role of nano-porosity. Our approach combines multi-scale analysis, integrating molecular dynamics simulations at the atomistic level with phase-field fracture methods at the continuum level. This allows us to capture critical material properties from the nanoscale, examining how variations in porosity, pore shapes, and their interactions influence the macroscopic mechanical and fracture behaviors. We will present several case studies to highlight the significant impact of nano-pore morphology on the overall fracture response of porous materials.
How to cite: Newell, P.: Phase-Field Fracture Modeling of Porous Materials Informed by Molecular Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20480, https://doi.org/10.5194/egusphere-egu25-20480, 2025.
The chalk cliffs of northern France are exposed to considerable erosion, resulting in a significant coastal retreat of up to 1 m per year on average. A key concern is how the mechanical properties of the chalk evolve under different weathering conditions. Previous research, based on a limited number of samples, has provided a preliminary understanding of potential changes in the mechanical properties of chalk in altered and unaltered states. As part of the DEPHY3GEO project, we conducted experiments on Saint Marguerite Chalk, which is part of the Newhaven Chalk Formation. Due to the inherent low strength of the chalk, some conventional displacement measurement techniques are inappropriate. Therefore, we used digital image correlation (DIC) coupled with basic acoustic measurements. Experiments were performed on chalk samples exposed to various weathering conditions, including salt solutions, fresh water, and thermal cycling. These experiments consisted of uniaxial and confined compression tests, which allowed us to evaluate the influence of weathering on the mechanical behavior of the chalk. Results show that water saturation of chalk rock significantly reduces by half or more its maximum compressive strength. Ongoing work will further investigate the weathering of chalk by studying its effect on micro- and macro-scale structures through structural analysis of cliff samples and scanning electron microscopy (SEM).
How to cite: Chalé, A., Bu, F., Jaboyedoff, M., Costa, S., Maquaire, O., and Kouah, M.: The Influence of Weathering on the Mechanical Properties of Chalk: Study of the Saint Marguerite Chalk , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11784, https://doi.org/10.5194/egusphere-egu25-11784, 2025.
Acoustic Emissions (AE), the laboratory analogs for seismic activity, offer a controlled environment to study deformation and failure mechanisms. By leveraging high-precision three-dimensional localizaton techniques, researchers can analyze ongoing these mechanisms during rock deformation experiments. The spatial resolution is thus crucial for increasing our capability to understand and predict failure modes in natural and engineered systems.
Despite recent advances in localization techniques, automated AE localization faces significant challenges. Conventional AE processing systems generally extract a limited set of parameters, such as arrival time defined as the first overcoming a given amplitude threshold. While these parameters provide the bulk information, they often overlook critical signal aspects, underestimating AE phenomena complexities and compromising the localization accuracy. In fact, amplitude thresholds may not capture accurately the signal onset, particularly in noisy or complex waveforms.
This study proposes a new methodology to improve source location accuracy and AE event classification by developing an automatic picking system tailored to seismic signal characteristics and set on Signal-to-Noise Ratio (SNR). The novel algorithm introduced here overcomes conventional amplitude-based thresholding by including broader waveform characteristics, source-receiver distance and wave propagation path. The analysis operates on multiple signal windows and provides uncertainty estimates, enabling more accurate AE location.
The AE source localization process was carried out using the Time Difference Of Arrival (TDOA) method, widely applied in rock deformation laboratory experiments. This approach considers signal arrival time differences at multiple transducers and, with a velocity model, estimates the three-dimensional coordinates of AE sources. The localization quality was assessed via four key parameters: 1) RMS (Root Mean Square) between observed and calculated arrival times, 2) localization errors along the three principal coordinates, 3) MAPE (Mean Absolute Percentage Error quantifying arrival time differences), and 4) the average azimuthal gap across three principal planes. These parameters quantify discrepancies in location accuracy and are employed to assess the final localization.
We applied our methodology to waveform data of AE recorded by an array of twelve 1 MHz piezo-electric transducers during conventional triaxial deformation of a 40 × 100 mm Darley Dale sandstone cylindrical sample (King et al., 2021) at 20 MPa confining pressure. We show that our approach reduces the localization errors and improves the AE detection and localization accuracy. By addressing conventional AE location limitations, this work advances AE-based monitoring toward more accurate and reliable results, providing higher resolution and improved information to describe the damage micro-mechanisms driving failure in stressed rocks.
How to cite: Adinolfi, G. M., Chen, Y., and Vinciguerra, S. C.: Acoustic Emission Source Localization Techniques: A Methodology for Improved Localization Accuracy in Laboratory Deformation Experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12108, https://doi.org/10.5194/egusphere-egu25-12108, 2025.
Mineralogical composition and porosity significantly influence the mechanical behavior of hydrocarbon reservoir rocks in crustal conditions. To understand the mechanical failure behavior and dynamic porosity changes with axial loading, triaxial compression experiments were conducted, in three distinct reservoir rock types: KG Basin Sandstone, Bombay High limestone, and Boise Sandstone. Initial porosities of collected samples varied; with KG sandstone at 30%-32%, Bombay limestone at 9.5%-12.7%, and Boise sandstone at 20.6%-25%, determined under dry testing conditions. A range of effective pressures (Peff) was applied to investigate brittle faulting and cataclastic flow under dynamic axial loading. Both Boise and KG sandstones transitioned from a brittle dilatant regime to a compactive cataclastic flow regime, with Boise sandstone displaying brittle behavior up to 5 MPa Peff and KG sandstone up to 50 MPa Peff. Conversely, the Bombay limestone consistently exhibited compactive cataclastic flow at all tested experimental conditions. KG sandstone demonstrated highest peak strength relative to the other rock types due to its lower porosity. Additionally, Boise sandstone showed higher peak strength than Bombay limestone, primarily due to the presence of quartz within the sandstone matrix, which is more resistant relative to the carbonate minerals of limestone formations. In KG sandstone, there was a significant increase in porosity prior to sample failure, particularly up to 70 MPa Peff, and the final porosity observed post-failure surpassed the initial porosity levels recorded, upto 50 MPa Peff. In contrast, both Boise sandstone and Bombay limestone showed a continuous decrease in porosity with increasing differential loading throughout the experiment at all tested conditions. Deflection patterns of triaxial curves indicated a shift from shear-induced dilation to shear-enhanced compaction in both Boise sandstone (dilation up to 5 MPa Peff) and KG sandstone (dilation up to 50 MPa Peff), while the Bombay limestone predominantly displayed shear-enhanced compaction across all tested Peff beyond a critical stress threshold. KG sandstone exhibited a transition from pre-failure dilatant to post-failure compactive inelastic strain with increasing Peff, which contrasts with the post-failure compactive inelastic strain that was consistently observed in the case of the Bombay limestone.
By integrating these petrophysical and mechanical parameters into reservoir management, hydrocarbon extraction can be made more effective and safer. These insights are essential for creating accurate geomechanical models, which are vital for strategic field operation planning, optimizing production rates, and maintaining reservoir stability.
How to cite: Dasgupta, A., Saha, P., Bal, A., and Misra, S.: Influence of triaxial compaction on the mechanical behaviour and porosity evolution of reservoir rocks., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6063, https://doi.org/10.5194/egusphere-egu25-6063, 2025.
Rocks exhibit astonishing time dependent mechanical properties, like memory of experienced stress or slow dynamics, which refers to a transient recovery of stiffness after a softening induced by almost any type of loading. This softening and transient recovery is observed in the subsurface and in buildings after earthquake shaking, or in laboratory samples.
Our investigation of anisotropy of the slow dynamics effect under uniaxial loading in dry sandstone samples shows that it is observed independent of propagation direction, while the loading effect shows the expected anisotropy originating from the opening and closing of cracks. These observations put a number of novel constraints on the enigmatic physics of slow dynamics.
We conclude that transient changes in bulk stiffness are caused by sliding of oblique grain-to-grain contacts and resulting changes in frictional properties as empirically described by rate-and-state friction and observed in laboratory experiments across block contacts.
Connecting the nonclassical nonlinearity of heterogeneous materials to the powerful framework of rate-and-state friction provides an elegant explanation for the long searched-for origin of slow dynamics and potentially adds a new perspective for the monitoring of very early stages of material failure when deformation is still distributed in the bulk and just starts to coalesce towards a fracture.
Similar experiments conducted are conducted with fluid saturation under varying confining and effective pressures illuminate the complex impact of pore fluids on the slow dynamics response of the material.
How to cite: Asnar, M., Sens-Schönfelder, C., Bonnelye, A., Curtis, A., Dresen, G., and Bohnhoff, M.: Anisotropy reveals contact sliding and aging as a cause of post-seismic velocity changes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13545, https://doi.org/10.5194/egusphere-egu25-13545, 2025.
The formation of surface-parallel exfoliation fractures, or “sheeting joints,” in rock domes produces some of the most intriguing and celebrated landforms on Earth. In 1904, G.K. Gilbert outlined three mechanisms for exfoliation fracture formation: (1) contraction during original cooling, (2) decompression during exhumation, and (3) post-exhumation surface processes. Recent research, including direct measurements during spontaneous exfoliation, has emphasized the influence of solar heating on progressive (subcritical) fracture propagation. This study investigates the mechanisms driving exfoliation fracturing at Arabia Mountain, a biotite orthogneiss dome near Atlanta, Georgia (USA), which experienced a spontaneous exfoliation event in July 2023. Digital elevation model differencing and field observations revealed the event uplifted a ~250 m² area by ~30 cm, buckling sheets up to 12 cm thick, and leaving traces of rock fragments and dust thrown meters away from fractures. Following this event, we installed instrumentation during the summer of 2024 to monitor surface-parallel stresses, local seismic activity, and subsurface rock temperatures at the site. Multiple subsequent exfoliation events in June 2024 were captured in real-time, including direct observations of progressive fracture propagation and dynamic rupture during a period of high temperatures. Relative surface-parallel stresses measured at variable depths in two boreholes revealed clear daily cycles that appear correlated with diurnal patterns of solar heating. A decrease in stress magnitudes and rock temperatures and increased lag time with depth further supports links between rock stresses and solar heating at the surface.
These observations support the hypothesis that subcritical cracking can be initiated or propagated due to thermal stresses and highlight the critical role of solar heating in progressive rock fracturing. The implications of these findings extend beyond Arabia Mountain. The sensitivity of rock domes to thermally induced stresses elevate concerns for an increased hazard of spontaneous exfoliation and rockfall events with future climate warming. Understanding the interplay between thermal stresses, mechanical fracturing processes, and pre-existing damage is critical for predicting such hazards and improving mitigation strategies. Furthermore, our observations and monitoring results provide valuable insights into the fundamental mechanics of subcritical fracturing, which can aid in determining the influence of surface weathering and erosion—key processes impacting the evolution of rock domes. We highlight the importance of multidisciplinary research in advancing our understanding of exfoliation joint formation, and more broadly towards disentangling the impacts of climate change on rock dome stability and landscape evolution.
How to cite: Reynolds, A. N., Eppes, M. C., Collins, B. D., Peng, Z., and Lang, K. A.: Influence of solar heating on spontaneous rock exfoliation at Arabia Mountain, Georgia, USA, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12839, https://doi.org/10.5194/egusphere-egu25-12839, 2025.
Rock fracturing plays a key role in both the formation of mountain landscapes and natural hazards. Weathering agents, such as daily thermal variations and precipitation, are some of the main triggers of the weathering and fracturing process. However, the mechanisms involved are not well understood, and questions remain about the thermo-mechanical stress field in the near surface of cliffs.
To better understand the effect of thermal variation on mechanical stress variation at centimeter to meter scales, long-term recordings were made using repeatable ultrasonic acoustic sensors to measure both esound velocity and waveform changes. The acoustic sensors were placed on a few square meters of a 50 m limestone cliff above Chauvet Cave in the Ardeche region of southeastern France.
The results show that daily cycles of velocity changes are evident and appear to correlate with thermal fluctuations and variations in solar radiation. We propose that the velocity variations are due to thermal stress variations in the rock. During the hottest part of the day, the velocity variation causes an increase in compressive hydrostatic stress. At the same time, the spectral analysis of the impulse response shows daily variations with the appearance of high frequency content during the hottest part of the day. Thus, we propose that the hottest times of the day have the effect of expanding the rock surface and thus closing the fractures, which increases the high frequencies content. Conversely, during cooling periods, we can detect tensile stresses that are likely to open fractures and contribute to progressive subcritical cracking within the rock mass.
This work was funded by the European Research Council (ERC) under grant No. 101142154 - Crack The Rock project
How to cite: Rousseau, R., Starke, J., Guillemot, A., Baillet, L., Moreau, L., and Larose, E.: Time-lapse ultrasonic testing for monitoring stress and structural changes in rock cliffs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15953, https://doi.org/10.5194/egusphere-egu25-15953, 2025.
Inherent complex internal architecture within fault zones, governed by diverse geological factors, results in heterogeneous mechanical variability, causing uncertainties in subsurface ground conditions. Therefore, understanding the spatial variations in mechanical stability in a fault zone is crucial to appropriate engineering mitigation plans and cost reduction for surface or subsurface infrastructure projects. The Great Glen Fault (GGF) is one of the major NE–SW trending strike-slip faults in Scotland, exhibiting complex internal architecture resulted from the multiple reactivation events and exhumation. The Torcastle block, a fault-bounded sliver within the fault core of the GGF, contains heterogeneous micaceous shear zones, faults, and local dykes cutting foliated psammitic–pelitic gneiss and quartzite. At the Torcastle block, this study synthesizes the parallel structural geological and engineering approaches to decipher the relationship between structural features and mechanical stability by mapping structural domains, topological nodes, fracture densities, and engineering Q-values. Four fracture types are classified based on the spatial distribution pattern and geometrical relationships with local faults and foliations. The heterogeneous spatial patterns of faults, fractures, and foliations at the Torcastle block define several fault-bounded structural domains. The geometrical properties of fractures are highly variable, but they clearly relate to the dyke distribution and local foliation trend in each domain. Mechanically weak zones, represented by low Q-values, are highly heterogeneous but concordant with the areas of high fracture and topological X and Y node density. These mechanically unstable zones are typically related to the following structural features in a fault zone, including major shear or fault strands and embedded blocks, intruded igneous dykes, abutting areas of faults with different orientations, and highly rotated blocks showing re-oriented local foliations. Correlation analysis between Q-values and other parameters, including fracture density, RQD, Jn, Jr, and X and Y node density, reveals different contributing patterns of each parameter to mechanical stability in each structural domain. Especially, the zone of highly rotated local foliations exhibits lower mechanical stability, despite relatively low fracture densities compared to other mechanically weak zones, due to increased fracture orientation variability and connectivity. The results of this study highlight the heterogeneous internal architecture of fault zones and their relationships with mechanical stability distribution, which shed insight into forecasting mechanically weak zones in rock masses and reducing geotechnical risks for subsurface engineering projects.
How to cite: Kim, N., Zoe K., S., Yannick, K., and Christopher D., J.: Deciphering Heterogeneous Mechanical Stability in an Exhumed Fault Zone through a Structural-Geotechnical Approach: A Case Study from the Great Glen Fault, Scotland., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11919, https://doi.org/10.5194/egusphere-egu25-11919, 2025.
With the increasing exploration of the Bohai Bay area, deeply buried metamorphic rock paleoreef reservoirs have become a key focus of exploration. These reservoirs typically consist of fractures and dissolution cavities, exhibiting strong heterogeneity and characteristics of low porosity and permeability. Their pore structures are extremely complex, which brings considerable uncertainty to the classification of reservoir effectiveness. At the same time, the contribution of the rock skeleton to the resistivity logging values in metamorphic rock paleoreef reservoirs is much higher than that of formation fluids. Consequently, conventional fluid identification methods based on resistivity logging are significantly limited in these types of reservoirs. Thus, the effectiveness classification and fluid identification of metamorphic rock paleoreef reservoirs pose a considerable challenge to logging personnel.
This paper conducts an in-depth analysis of the logging response characteristics of pulse neutron logging in metamorphic rock paleoreef reservoirs, specifically the counting rates of inelastic gamma rays, the decay rates of gamma rays over time, and the counting rates of thermal neutron capture gamma rays. It proposes a novel method for fluid property identification in metamorphic rock paleoreef reservoirs using pulse neutron logging.
The analysis reveals that the gamma counting rate of the far-detector of pulse neutron logging is significantly influenced by high-density minerals such as biotite and pyroxene. A method for correcting the gamma counting rate based on lithology calibration for high-density rocks is thus introduced. When the reservoir contains gas or is a gas layer, the gamma long-short source distance counting rate for inelastic collisions shows a distinct “intersection” characteristic. This feature can effectively identify gas layers. When the reservoir is a liquid-bearing layer, a novel fluid identification method based on the reconstruction of the rock skeleton's relative atomic weight curve is proposed. This method first optimizes the multi-mineral model based on X-ray diffraction analysis to calibrate mineral content, then calculates the relative atomic weight of minerals based on the mineral element content, and finally derives the theoretical relative atomic weight curve for the rock skeleton along the entire well section. The effective reservoir is identified using the intersection feature between this theoretical curve and the macroscopic thermal neutron capture cross-section curve obtained from pulse neutron logging. Additionally, oil-water layers are discriminated based on oil and gas shows recorded in the field.
This innovative method for correcting the gamma counting rate based on lithology and reconstructing the relative atomic weight curve for fluid identification has been successfully applied to the effectiveness classification and fluid identification of the Paleoproterozoic paleoreef reservoirs in the BZ26 and BZ27 oilfields in the Bohai Bay. The logging interpretation accuracy exceeds 85%, which partially addresses the limitations of conventional resistivity logging in evaluating Paleoproterozoic paleoreef reservoirs.
How to cite: Meng, L., Li, J., and Xu, M.: Research on the Effectiveness Classification and Fluid Identification Methods of Complex Paleoreef Reservoirs Based on Pulse Neutron Logging, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8171, https://doi.org/10.5194/egusphere-egu25-8171, 2025.
Through the application of Multi-temporal Interferometric Synthetic Aperture Radar (MTInSAR) for long-term monitoring of surface deformation, the Agency of Rural Development and Soil and Water Conservation (ARGSWC), Ministry of Agriculture, has identified 315 deep-seated landslide sites with protecting targets across Taiwan as of 2024. For this study, imagery from January 2022 to October 2023 from the ALOS-2 satellite, released by the Japan Aerospace Exploration Agency (JAXA), is used for the MTInSAR monitoring. Based on the MTInSAR surface displacement data, activity indices for the deep-seated landslide sites have been developed, including both the arithmetic mean and inverse area-weighted deformations. The k-mean clustering and risk matrix method are then employed to classify and rank the landslide activity. The analysis reveals that approximately 5.8%, 10.7% and 83.6% of the deep-seated landslide sites are classified as high, medium and low activity, respectively. In addition, statistical clustering techniques are applied to group the surface deformation data, which are then compared to slope units derived from the aerial LiDAR Digital Elevation Model (DEM) for the landslide sites. This approach helps to identify active landslide blocks or subzones within the landslide sites.
How to cite: Kuo, C.-Y., Au, S.-Y., Chan, Y.-H., Chen, R.-F., Chan, K.-C., Lin, E.-J., and Tsai, P.-W.: Monitoring Surface Deformation and Classifying Activity of Deep-Seated Landslide Sites Using Multi-Temporal InSAR, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14383, https://doi.org/10.5194/egusphere-egu25-14383, 2025.
Due to the increasing impacts of global climate change in recent years, nations around the world have been grappling with frequent natural disasters. Taiwan, situated on the Pacific Rim seismic belt, is shaped by active orogeny, resulting in its rugged terrain. The island has experienced numerous typhoons, extreme rainfall, and complex hydrological conditions, making its mountainous areas particularly vulnerable to natural disasters. The accumulation of soil and sediment further alters the landscape of its watersheds, putting both infrastructure and residents at significant risk. This study therefore focuses on the monitoring and maintenance of slopes in Taiwan’s watershed areas.
Since the inspection of mountain roads is limited by terrain and vegetation, this study utilizes the high-resolution Digital Elevation Model (DEM) for geomorphometric analysis to precisely target landslide hot spots, and Unmanned Aerial Vehicles (UAVs) to observe more detailed topographical features. Meanwhile, the Normalized Difference Vegetation Index (NDVI) is used to interpret landslide and vegetation restoration status, while Multi-Temporal InSAR (MTInSAR) is employed to detect topographical changes and observe post-disaster alterations.
Taking the section between Chinhe and Fuxing (92K to 99K) of Taiwan Provincial Highway 20 as a case study, this highway serves as a critical horizontal transportation hub. Following the impact of Typhoon Morakot in 2009, the region has experienced highly unstable and complex hydrological conditions, resulting in persistent damage to its roads and bridges. This study primarily employs high-resolution LiDAR DEM to analyze pre- and post-disaster changes in terrain and river channels. Then the NDVI interpretation, derived from SPOT satellite imagery, reveals that the crown of the original landslide area has been actively developing, leading to the movement of rocks and debris. The MTInSAR results further corroborate this interpretation, confirming that the crown area of Yushui River remains prone to landslides, with new slide events and significant sediment accumulation in downstream areas.
In summary of the analysis and on-site data, the primary disaster-prone factors are the meandering of the Lanong River and the accumulation of soil and sand, leading to extreme instability in the alluvial fans on both banks. After multiple landslides, the damage mechanism is analyzed, revealing that the region is highly susceptible to tectonic activity. The initial results facilitate the overall slope stability evaluation and provide relevant agencies with governance and maintenance recommendations to enhance road safety.
Keyword：High-resolution Digital Elevation Model, DEM、Normalized Difference Vegetation Index,NDVI、Multi Temporal InSAR, MT-InSAR.
How to cite: Huang, Y.-T., Chen, R.-F., Chang, K.-J., Chen, T.-H., Chang, C.-S., Wang, C.-H., Syu, S.-J., Chuang, H.-K., and Chi, C.-Y.: Using high-resolution geomorphometry and normalized difference vegetation index (NDVI) to assess slope stability in the watersheds of Taiwan: A case study of the section between Chinhe and Fuxing, from 92K to 99K of Taiwan Provincial Highway 20., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16144, https://doi.org/10.5194/egusphere-egu25-16144, 2025.
Accurate initial geostress state is a prerequisite for the dynamic optimization design and construction of deep-buried tunnels, as well as for preventing disasters such as rockburst and large deformation. Inversion methods of the stress field for underground engineering, which utilize limited measurement data and numerical simulation techniques, have emerged as the primary approach. However, traditional inversion optimization models often treat stress components as independent scalars. This simplification overlooks issues of physical consistency and optimization complexity. Additionally, existing intelligent inversion methods, such as machine learning and heuristic optimization, require a large number of simulations, posing a challenge in balancing accuracy and efficiency. This issue becomes particularly problematic for large-scale tunnels in complex geological conditions where the computational time cost is exorbitantly high, thereby hindering the practical need for quick and precise stress field reconstruction.
To address these challenges, we propose a novel inversion method that integrates a tensor-based objective function with Bayesian optimization (TOF-BO). Concretely, this method regards the stress tensor as a whole, uses the Euclidean distance to measure the deviation between calculated and measured values during optimization, and formulates the objective function as the sum of deviations across all measurement points. Unlike traditional scalar objective functions, this tensor-based objective function preserves the physical correlations between stress components, reduces the dimensionality of the objective function, and effectively avoids the adverse effects of magnitude differences between components on optimization efficiency and accuracy. Given the objective function's dependency on costly simulation, we adopt Bayesian optimization, utilizing active learning to achieve global and efficient optimization.
This method was applied at the engineering site of a deep-buried tunnel under construction in southwestern China. The results showed that the TOF-BO method yielded satisfactory results (average accuracy=90.8%) with only 18 time-consuming numerical simulations, proving that the method can significantly reduce the demand for expensive simulations, effectively decrease computational costs, and possesses the ability to rapidly and reliably reconstruct the stress field within the study area. Compared to commonly neural network methods, the TOF-BO method improves accuracy by approximately 4.6% within the same time cost. In conclusion, the TOF-BO method provides an efficient and reliable solution for the inversion of geostress fields, demonstrating substantial potential for practical applications.
How to cite: Li, T. and Wei, D.: An Efficient Geostress Inversion Method and Its Application under Complex Geological Conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1749, https://doi.org/10.5194/egusphere-egu25-1749, 2025.
The Kırık Tunnel in Erzurum is an important route in the highway network designed to connect the northern and southern regions of Turkey. The tunnel, planned to be 7 km long, 10 m high and 7 m wide, passes through a geologically complex region. Preliminary investigations have revealed that the tunnel route is predominantly composed of clayey limestone and marl succession with variable slopes and orientations. During the tunnel construction works, a cave-in occurred during excavation after the water flow and a fault zone containing sandy-gravelly and organic matter was encountered at the 1+825+70 km section of the tunnel. The discovery of the crushed zone due to faulting necessitated a change in the tunnel design and it was decided to apply the back analysis method to understand the collapse mechanism. The deformation data affecting the tunnel were obtained with the help of load cells and back analysis was performed to determine the parameters of the collapse material from this deformation value at the time of collapse. Rock mass classifications were made using the parameters obtained from field and laboratory observations. As a result, with the help of Rocscience RS2, the collapse in the Kırık Tunnel was analyzed by finite element method and back analysis was performed. During the back analysis, the lateral vertical stress pressure acting on the faulted weak zone had to be re-evaluated. The k value changes in the numerical calculation model were examined from the existing approach methods and the comparison of these methods depending on the deformations in tunnel construction was given within the scope of the study. As a result of these data, new design parameters were found and grouting and support recommendations were given to overcome the stability problems in the tunnel. Accordingly, the lateral vertical stress ratio was taken as 1.6, which is normally 0.3, and the lateral pressure in the tunnel was determined as higher than the vertical pressure. With the new parameters, the unstable zone in the tunnel was theoretically crossed without any problems.
How to cite: Eslik, O., Undul, O., and Dogu, M. M.: The Effects of Unstable Fault Zones on Design Parameters of Tunnels (The Case of Erzurum Kırık Tunnel), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12997, https://doi.org/10.5194/egusphere-egu25-12997, 2025.
The tensile strength of brittle rocks is commonly determined experimentally using the Brazilian test (splitting tensile strength test). For spatial and temporal upscaling of these experimental results, numerical methods are necessary to predict rock behaviour under complex geomechanical conditions such as foundation, slope stability, underground space and reservoirs studies, and to analyse the influence of individual parameters on the outcomes.
Previous studies on phase-field modeling of rocks often employed a single open flaw to simulate fracture initiation, and two to four open flaws to represent fracture propagation and failure. These flaws were generally arranged in a geometrically ordered pattern. However, in natural rock formations, microfractures are predominantly closed and exhibit a more or less random distribution depending on texture.
This study used a phase-field model to simulate brittle fractures in granite containing multiple randomly distributed, closed pre-existing microcracks, employing the principal stress criterion as the driving force in the phase-field evolution equation.
This study focuses on analyzing the sensitivity of the model to crack density, spatial distribution, and phase-field parameters. The effect of displacement rate was investigated, and phase-field parameters were calibrated accordingly. To demonstrate the presented approach's accuracy, numerical simulations are compared to experimentally obtained results showing that the approach is in principle capable of temporal and spatial upscaling when microstructural features are considered.
How to cite: Asghari Chehreh, H., Witte, L., Duda, M., and Backers, T.: Simulation of displacement rate effect on tensile rock failure using a phase-field fracture approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15632, https://doi.org/10.5194/egusphere-egu25-15632, 2025.
After fifty years of mantle plume theory, the cause and effect remain subjects of intense debate. The scientific community is divided between those who believe that mantle plumes are fueled by a deep mantle source and those who argue for a shallow process related to plate tectonics. Although both the plume and plate hypotheses relate to the effect of thermal anomaly, few studies have attempted to explain the formation of initial thermal instability or the maintenance of magma sources for volcanism and large igneous provinces (LIPs). In this study, by considering the putative link between mantle dynamics, lithospheric breakup and flood basalts, we employ a three-dimensional spherical shell model to simulate the Earth's rifting process under thermal expansion. Based on the physical principles for the phase change of materials, we invoke a qualitative model of decompression-melting generation in rifting-induced abnormally-hot asthenosphere to explain that extra volume growth during the material phase change from solid to liquid can promote the coupling effect between pressure and temperature. Our fracture modeling shows that the shallow-based lithospheric process favors a no-root mantle plume as the source for volcanism. Continental rifting and breakup may be caused by the heat accumulation within the asthenosphere underneath the lithosphere, without the need for the existence of deep mantle plumes. Inversely, the fractures, particularly around triangle conjunctions, may release the stresses around their tips and accelerate the decompression melting, which in turn results in the thermal anomaly underneath the lithosphere inside which fractures develop. Our results reveal that pressure drops caused by uplift-induced rifting can accelerate decompression melting and provide the magma source for potential eruptions. Additionally, the significant increase in magma pressure, resulting from the abrupt volume expansion during the solid-to-liquid phase change, may act as the driving force of magma production. This process can become unstable if the coupling between melting pressure and temperature operates as a positive feedback loop. Such instability may lead to mantle dynamics emerging in a top-down pattern, offering insights into the rapid and voluminous magma eruptions characteristic of LIPs. Namely, the accumulated heat may result in expansion in the mantle which may promote uplifting, weakening and eventual breakup of the lithosphere, with huge outpouring of flood basalts, leading to the great events of LIPs. Furthermore, the associated cooling of the lithosphere occurs due to heat absorption during melting and heat loss during eruptions. This process provides a clear understanding of the short-lived yet massive nature of LIPs.
How to cite: Tang, C., Gong, B., and Chen, T.: Investigation into the formation of large igneous provinces from the perspective of Earth's breakup and induced decompression melting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-146, https://doi.org/10.5194/egusphere-egu25-146, 2025.
