Unfrozen water content (UWC) is a key parameter affecting a variety of soil physical-mechanical properties and processes in frozen soil systems. However, traditional estimation models suffer limitations due to oversimplified assumptions or limited applicable conditions. Given that, there is a compelling need to explore alternative modeling approaches that leverage machine learning (ML) algorithms, which have shown increasing potential in engineering fields. To this end, this study evaluated and compared six widely known ML algorithms (i.e., three ensemble models: RF, LightGBM and XGBoost; and three non-ensemble models: KNN, SVR and BPNN) for modeling UWC based on collected experimental datasets. These algorithms were optimized and evaluated using a framework combining Bayesian optimization and cross-validation to ensure model stability and generalization. The results demonstrated that the ensemble tree-based methods, particularly LightGBM and XGBoost, achieved the highest predictive accuracy and superior overall performance. On the other hand, the nonensemble methods exhibited poorer generalization abilities. Interestingly, during 10-fold cross-validation, consistent underperformance was observed for a particular fold, possibly stemming from the challenges of the data distribution in that fold after random shuffling. The present study highlights the effectiveness of ensemble learning approaches, importance of proper hyperparameter tuning and validation strategies, and intrinsic modeling challenges arising from the difference between the freezing and thawing phase change behaviors. This comprehensive ML model comparison and robust training framework provide valuable guidance on selecting suitable data-driven techniques for modeling frozen soil properties for cold regions hydrogeology and engineering practices.

Geochemical alteration of host rocks might affect the productivity and the potential for induced seismicity of geothermal systems. In addition to natural alteration, following production and heat extraction, re-injected fluids at lower temperatures and different pressures may be in chemical disequilibrium with the rock, impacting mineral solubility and dissolution / precipitation processes. In this study, we investigate the effect of geochemical alteration on the frictional behaviour of granites, and their seismogenic potential, by conducting direct shear experiments using samples with varying degrees of alteration. The samples originate from the Carnmenellis granite in Cornwall, SW England, and represent the formation used in the United Downs Deep Geothermal Power Project for heat extraction. Experiments were conducted on granite powders (referred to as gouges) at room temperature and 180°C, at simulated in-situ confining and pore pressures of 130 MPa and 50 MPa, respectively (~5 km depth). With increasing degree of alteration, the frictional strength of the gouges decreases while frictional stability increases. At high temperature, frictional stability is reduced for all samples while maintaining the trend with alteration stage. Microstructural investigation of the sheared gouges shows alteration delocalises shear by reducing grain size and increasing clay fraction, which promotes the formation of pervasive shear fabrics. Our work suggests that, within the range of tested pressures, more alteration of granite initially causes more stable shearing in a fault. This behaviour with alteration is sustained at high temperatures, but the overall frictional stability is reduced which increases the potential for induced seismicity at higher temperatures.

Pore fluid pressure generated by dehydration of hydrous minerals can trigger deep and intermediate-depth earthquakes. To investigate its effect on frictional behaviors, we conducted friction experiments on simulated bassanite gouges and observed the stress drops and recurrence intervals of stick-slip events decreased over time under 200 MPa and 110 °C. Microstructural observations indicates that gouges deformed under room temperature shows the development of numerous shear bands including Riedel shears. On the other hand, a sample deformed under 200 MPa and 110 °C had few Riedel shear planes, indicative of the elevated pore fluid pressure suppressing the development of shear planes. We derived time function of dehydration-driven pore fluid pressure evolution using Avrami kinetics. Because of the mathematical similarity of Avrami equation and the fractal geometry, our result shows that the kinetics-driven pore fluid pressure evolution controlled the stick-slip behaviors of the basanite gouges under dehydration.

A document by Kristina Vrouwenvelder. Click on the document to view its contents.

Numerical modeling of the fabric of naturally deposited sands depends on being able to accurately reconstruct individual grains in a reasonable amount of time. To this end, X-Ray Computed Tomography (XRCT) is an excellent tool. However, while the currently available processing workflows, e.g. (Stamati, O., et al, 2020), have been successfully used to obtaining the shapes of clean, pluviated sands, the image reconstruction is a lot more challenging in resolving the individual grains and fabric of naturally deposited fine sands, such as shown in Figure 1. The focus of this study has been to develop a more robust that can rapidly reconstruct the grain avatars in sufficient detail.

The growth history of the Northeastern Tibetan Plateau (NETP) is enigmatic, with debates on when and how the NETP significantly uplifted. Here, we use a numerical landscape evolution model to quantitatively investigate the ~20 Ma growth history of the NETP by studying the formation history of the upstream Yellow River (UYR). Compared to the observed river profiles, erosion rates, the trend of acceleration time of deformation, and paleo-elevation, our modeling results suggest that the long-term growth history of the NETP consists of an early block uplift (~20-12 Ma) and a late outward propagation uplift (~12-0 Ma). Before ~12 Ma (middle Miocene), the NETP was uplifted via a block growth, with major uplift in the south part. Subsequently, the high (~5 km) NETP has been uplifted via a northward propagation growth until the present-day time. We further suggest that pure headward erosion unlikely formed the observed river profile of the UYR over the past few million years. Our modeling thus reconciles the long-term outward growth of the NETP and the UYR profile, suggesting a downstream migration of high erosion rates, which is fundamentally different from the headward erosion of small mountain rivers. The downstream propagation of fluvial erosion may commonly occur in the outward-growing plateau on Earth.

Temperature is of primary importance for many physical properties in the Martian soil. We measured diurnal and annual soil (and surface) temperature variations using the NASA InSight Mars mission’s HP3 radiometer and thermal probe. At the depth of the probe of 0.5 - 36 cm, an average temperature of 217.5K was found varying by 5.3 - 6.7 K during a sol and by 13.2K during the seasons. The damping of the surface temperature variations in the soil were used to derive a thermal diffusivity of 2.30±0.03×10−8 m2/s for the depth range of the diurnal wave - thermal skin depth 2.5±0.04 cm - and 3.74±0.61×10−8 m2/s for that of the annual wave, with a thermal skin depth of 84±10 cm. The temperatures measured are conducive to the deliquesence of thin films of brines in the soil. These are of astrobiological interest and may explain the formation of the observed cemented duricrust.

We analyze Kodiak, an eroded delta remnant in Jezero Crater, Mars, using several hundred images from the Mastcam-Z and SuperCam instruments on the Mars 2020 Perseverance Rover. We create a high-accuracy digital terrain model to measure Kodiak’s stratigraphic layers, which we divide into three units and characterize individually. While each unit possesses geometries interpreted as consistent with a Gilbert-style delta formation, the older units exposed on Kodiak’s north to northeast sides include more complex layered structures with azimuthally varying foresets. We compare Kodiak’s northeast foresets with the clinoforms of Whale Mountain, an outcrop exposed in the Western Jezero Delta scarp, and show similar azimuthally varying foresets. The stratigraphic analysis presented herein (strike and dip, unit thickness, etc.) will help test and refine detailed sedimentological hypotheses for the formation and evolution of the Jezero delta. Our 3D reconstruction and measurements enable unprecedented precision to evaluate depositional models and advance geological interpretation.

This study assessed total hydrocarbon content and polycyclic aromatic hydrocarbon content in Grönfjord (the Greenland Sea, Svalbard). The field study was held in marine expeditions of research vessel “Barentsburg” by the North-Western Branch of the Federal State Budget Institution, Research and Production Associaton «Typhoon» in summer periods of 2012 to 2022. In the framework of the field works simultaneous measurements of hydrological and hydrochemical characteristics of the water column were done. The data was analyzed using standard procedure in purpose to gather new information about the levels of hydrocarbons    (measured as total hydrocarbon contents), polycyclic aromatic hydrocarbons. The results showed pronounced interannual variations of total hydrocarbon contents and polycyclic aromatic hydrocarbons concentrations. Supposed that local natural sources contribute to elevated polycyclic aromatic hydrocarbons and total hydrocarbon content levels both in water and in sediments,  the levels of contamination do not signify exclusively anthropogenic influence on the sea-body. At the same time, some local elevated petroleum hydrocarbons concentrations, which were detected in the surface water layer, may be a sign of existing industrial activity affecting the waters of the fjord. Continuity of tasks starting from earlier expeditions indicates that many processes in the Norwegian Sea, Greenland Sea require further research.

In crustal faults dominated by granitoid gouges, the frictional-viscous transition marks a significant change in strength constraining the lower depth limit of the seismogenic zone. Dissolution-precipitation creep (DPC) may play an important role in initiating this transition, especially within polymineralic materials. Yet, it remains unclear to what extent DPC contributes to the weakening of granitoid gouge materials at the transition. Here we conducted sliding experiments on wet granitoid gouges to large displacement (15 mm), at an effective normal stress and pore fluid pressure of 100 MPa, at temperatures of 20-650°C, and at sliding velocities of 0.1-100 μm/s, which are relevant for earthquake nucleation. Gouge shear strengths were generally ~75 MPa even at temperatures up to 650°C and at velocities > 1 mm/s. At velocities ≤ 1 mm/s, strengths decreased at temperatures ≥ 450°C, reaching a minimum of 37 MPa at the highest temperature and lowest velocity condition. Microstructural observations showed that, as the gouges weakened, the strain localized into thin, dense, and ultrafine-grained (≤ 1 μm) principal slip zones, where nanopores were located along grain contacts and contained minute biotite-quartz-feldspar precipitates. Though poorly constrained, the stress sensitivity exponent n decreased from ≥17 at 20°C to ~2 at 650°C at the lowest velocities. These findings suggest that high temperature, slow velocity and/or small grain sizes promote DPC-accommodated granular flow over cataclastic frictional granular flow, leading to the observed weakening and strain localization. Field observations together with extrapolation suggest that DPC-induced weakening occurs at depths of 7-20 km depending on geothermal gradient.

Climate contrasts across drainage divides, such as orographic precipitation, are ubiquitous in mountain ranges, and as a result, mountain topography is often asymmetric. During glacial periods, these climate gradients can generate asymmetric glaciation, which may modify topographic asymmetry and drive divide migration during glacial-interglacial cycles. Here, we quantify topographic asymmetry caused by asymmetric glaciation and its sensitivity to different climate scenarios. Using an analytical model of a steady-state glacial profile, we find that the degree of topographic asymmetry is primarily controlled by differences in the Equilibrium Line Altitude (ELA) across the divide. Our results show that glacial erosion can respond to the same climate asymmetry differently than fluvial erosion. When there are precipitation differences across the divide, glacial erosion produces greater topographic asymmetry than fluvial erosion, all else equal. These findings suggest that glaciations may promote drainage reorganization and landscape transience in intermittently glaciated mountain ranges.

There is a lack of diversity amongst geoscience faculty. Therefore, many geoscience departments are taking steps to recruit and retain faculty from underrepresented groups. Here, we interview 19 geoscientists who identify as a member of an underrepresented race or gender who declined a tenure-track faculty job offer to investigate the factors influencing their decision. We find a range of key factors that influenced their decisions to accept or decline a position, including fit and resources, experiences during job interviews, negotiations and offers, family, geographic preferences, attention to DEI, personal identities, mentorship, hiring process, and teaching responsibilities. Despite existing recommendations for interventions to improve faculty diversity, many of the participants experienced hiring processes that did not follow these suggested best practices, suggesting that departments are not all aware of best hiring practices. Therefore, we leverage our results to provide actionable recommendations for improving the equity and effectiveness of faculty recruitment efforts. We find that institutions may doubly benefit from improving their culture: in addition to benefiting current members of the institution, it may also help with recruitment.

Sedimentary formations that compose most aquifers are difficult to model as a result of the nature of their deposition. Their formation generally involves multiple processes (alluvial, glacial, lacustrine, etc.) that contribute to the complex organization of these deposits. Representative models can be obtained using process-based or rule-based methods. However, such methods have several drawbacks: complicated parametrization, large computing time, and challenging, if not impossible, conditioning. To address these problems, we propose a new hierarchical surface-based algorithm, named EROSim. First, a predefined number of stochastic surfaces are simulated in a given order (from older to younger). These surfaces are simulated independently but interact with each other through erosion rules. Each surface is either an erosive or a deposition surface. The deposition surfaces represent the boundaries of depositional events, whereas the erosive surfaces can remove parts of the previously simulated deposits. Finally, these surfaces delimit sedimentary regions that are filled with facies. The approach is quite simple, general, flexible, and can be conditioned to borehole data. The applicability of the method is illustrated using data from fluvio-glacial sedimentary deposits observed in the Bümberg quarry in Switzerland.

A document by PRARABDH TIWARI. Click on the document to view its contents.

The Karakoram fault is an important strike-slip boundary for accommodating deformation following the India-Asia collision. However, whether the deformation is confined to the crust or whether it extends into the mantle remains highly debated. Here, we show that the Karakoram fault is overwhelmingly dominated by crustal degassing related to a 4 He-and CO 2rich fluid reservoir [e.g., He contents up to ~1.0−1.6 vol.%; 3 He/ 4 He = 0.029 ± 0.016 R A (1σ, n = 50); CO 2 /N 2 up to 3.7−57.8]. Crustal-scale active deformation driven by strike-slip faulting could mobilize 4 He and CO 2 from the fault zone rocks, which subsequently accumulate in the hydrothermal system. The Karakoram fault may have limited fluid connections to the mantle, and if any, the accumulated crustal fluids would efficiently dilute the uprising mantle fluids. In both cases, crustal deformation is evidently the first-order response to strike-slip faulting.

The end-Triassic extinction (ETE) is one of the most severe biotic crises in the Phanerozoic. This event was synchronous with volcanism of the Central Atlantic Magmatic Province (CAMP), the ultimate cause of the extinction and related environmental perturbations. However, the continental weathering response to CAMP-induced warming remains poorly constrained. Strontium isotope stratigraphy is a powerful correlation tool that can also provide insights into the changes in weathering regime but the scarcity of 87Sr/86Sr data across the Triassic-Jurassic boundary (TJB) compromised the use of this method. Here we present new high-resolution 87Sr/86Sr data from bulk carbonates in Csővár, a continuous marine section that spans 2.5 Myrs across the TJB. We document a continuing decrease in 87Sr/86Sr the from the late Rhaetian to the ETE, terminated by a 300 kyr interval of no trend and followed by a transient increase in the early Hettangian that levels off. We suggest that the first in the series of perturbations is linked to the influx of non-radiogenic Sr from the weathering of freshly erupted CAMP basalts, leading to a delay in the radiogenic continental weathering response. The subsequent rise in 87Sr/86Sr after the TJB is explained by intensified continental crustal weathering from elevated CO2 levels and reduced mantle-derived Sr flux. Using Sr flux modeling, we also find support for such multiphase, prolonged continental weathering scenario. Aggregating the new dataset with published records employing an astrochronological age model results in a highly resolved Sr isotope reference curve for an 8.5 Myr interval around the TJB.

• MARSIS radar sounder data reveals layering in the Medusae Fossae Formation deposits. • Layers are likely due to transitions between mixtures of ice-rich and ice-poor dust, analogous to those in Polar Layered Deposits. • An ice-rich portion of the MFF deposit may contain the largest volume of water in the equatorial region of Mars.

Surface deformation associated with continental earthquake ruptures includes localized deformation on the faults, as well as deformation in the surrounding medium though distributed and/or diffuse processes. However, the connection of the diffuse part of the surface deformation to the overall rupture process, as well as its underlying physical mechanisms are not yet well understood. Computing high-resolution optical image correlations for the 2021/05/21 Mw7.4 Maduo, Tibet, rupture, we highlight a correlation between the presence of faults and fractures at the surface, and variations in the across-fault displacement gradient, fault zone width, and amplitude of surface displacement. We show that surface slip along primary faults is systematically associated with gradients greater than 1%, and is dominant in regions of greater coseismic surface displacement. Conversely, the diffuse deformation is associated with gradients ≤0.3%, and is dominant in regions of lesser surface displacement. The distributed deformation then occurs for intermediate gradients of 0.3-1%, and at the transition between the localized and diffuse deformation regions. Such patterns of deformation are also described in laboratory experiments of rock deformation, themself supported by field observations. Comparing these experiments to our observations, we demonstrate that the diffuse deformation along the 2021 Maduo rupture corresponds to kilometer-wide plastic yielding of the bulk medium occurring in regions where surface rupture is generally missing. Along the 2021 Maduo rupture, diffuse deformation occurs primarily in the epicentral region, where the dynamic stresses associated with the nascent pulse-like rupture could not overcome the shallow fault zone frictional strength.

This study aims to explore the potential of underground hydrogen storage, its effects on rock formations, and the subsequent implications for energy and environmental sustainability.

Microcontinents are globally recognized as continental regions partially or entirely surrounded by oceanic lithosphere. Due to their positioning, they may become entangled in subduction zones and undergo either accretion or subduction. High-pressure metamorphism in subducted continental rocks support the idea that microcontinents can be subducted, regardless of their low densities. In this study, we used 2D numerical models to simulate collision of microcontinents with different sizes located at various distances from the upper plate in a subduction system characterized by different convergence velocities, in order to examine their effects on the thermo-mechanical evolution of subduction systems. Specifically, we analyzed the conditions that favor either subduction or accretion of microcontinents and investigated how their presence affects the thermal state within the mantle wedge. Our results reveal that the presence of microcontinents can lead to four styles of subduction: 1) continuous subduction; 2) continuous subduction with jump of the subduction channel; 3) interruption and restart of the subduction; 4) continental collision. We discovered that larger microcontinents and higher velocities of the subducting plate contrast a continuous subduction favoring accretion, while farther initial locations from the upper plate and higher velocities of the upper plate favor the subduction of the microcontinent. Additionally, we observed that the style of subduction has direct effects on the thermal state, with important implications for the potential metamorphic conditions recorded by subducted continental rocks. In particular, models characterized by parameters that favor the subduction of a larger amount of continental material from the microcontinent exhibit warm mantle wedges.

Geometric characteristics of subaqueous bedforms, such as height, length and leeside angle, are crucial for determining hydraulic form roughness and interpreting sedimentary records. Traditionally, bedform existence and geometry predictors are primarily based on uniform, cohesionless sediments. However, mixtures of sand, silt and clay are common in deltaic, estuarine, and lowland river environments, where bedforms are ubiquitous. Therefore, we investigate the impact of fine sand and silt in sand-silt mixtures on bedform geometry, based on laboratory experiments conducted in a recirculating flume. We systematically varied the content of sand and silt for different discharges, and utilized a UB-Lab 2C (a type of acoustic Doppler velocimeter) to measure flow velocity profiles. The final bed geometry was captured using a line laser scanner. Our findings reveal that the response of bedforms to an altered fine sediment percentage is ambiguous, and depends on, among others, bimodality-driven bed mobility and sediment cohesiveness. When fine, non-cohesive material (fine sand or coarse silt) is mixed with the base material (medium sand), the hiding-exposure effect comes into play, resulting in enhanced mobility of the coarser material and leading to an increase in dune height and length. However, the addition of weakly-cohesive fine silt reduces the mobility, suppressing dune height and length. Finally, in the transition from dunes to upper stage plane bed, the bed becomes unstable and bedform heights vary over time. The composition of the bed material does not significantly impact the hydraulic roughness, but mainly affects roughness via the bed morphology, especially the leeside angle.

Micromagnetic modelling allows the systematic study of the effects of particle size and shape on the first-order reversal curve (FORC) magnetic hysteresis response for magnetite particles in the single-domain (SD) and pseudo-single domain (PSD) particle size range. The interpretation of FORCs, though widely used, has been highly subjective.  Here, we use micromagnetics to model randomly oriented distributions of particles to allow more physically meaningful interpretations.  We show that one commonly found type of PSD particle - namely single vortex (SV) particles - has far more complex signals than SD particles, with multiple peaks and troughs in the FORC distribution, where the peaks have higher switching fields for larger SV particles. Particles in the SD to SV transition zone have the lowest switching fields. Symmetrical and prolate particles display similar behavior, with distinctive peaks forming near the vertical axis of the FORC diagram. In contrast, highly oblate particles produce `butterfly' structures, suggesting that these are potentially diagnostic of particle morphology. We also consider FORC diagrams for distributions of particle sizes and shapes and produce an online application that users can use to build their own FORC distributions.  There is good agreement between the model predictions for distributions of particle sizes and shapes, and the published experimental literature.

Mapping of the basement relief in regions of a high geological importance is key to mineral prospecting. In this study, we estimate the sediment thickness within the Southern Benue Trough of Nigeria by using synthetic Bouguer gravity data alongside 113 logged borehole data to validate the gravimetric inversion and interpretation. A 3-D gravimetric inversion of the residual gravity data was carried out to determine the thickness of sedimentation after a regional-residual gravity separation. Our numerical results (ranging from 0.8 to 5.5 km) have almost no systematic bias (mean value = 0.045) when compared with the 113 measured sediment depths obtained from drilling profiles. The estimated sediment depths closely mimic the known geological structures and tectonic complexities of the highly rifted Southern Benue Trough of Nigeria. The synthetic Bouguer gravity map exhibits a spatial pattern that indicates possible magmatic movements, which could have led to shallow sediments over and along the Abakaliki Anticlinorium. This elevated crust (because of an upward magmatic movement) created crevices, faults, folds, ridges, or troughs that must have paved way for a thick sedimentary cover that possibly have matured overtime (because of a high temperature) into important habitats for mineral resources. We conclude that the very thick sedimentary cover at the southwestern portion of the study area may have been brought about by a compaction or compression of tectonic plates thereby generating adequate heat and pressure for the maturation of several mineral resources at the Southern Benue Trough of Nigeria.   Keyword: Bouguer gravity maps; gravity inversion; sediment thickness; Regional-residual gravity separation; mineral exploration

The Urgent Computing Integrated Services for Earthquakes (UCIS4EQ) is proposed as a novel Urgent Computing (UC) seismic workflow that focuses on short-time reports of synthetic estimates of the consequences of moderate to large earthquakes. UC combines High-Performance Computing (HPC), High-Performance Data Analytics (HPDA), and optimized solvers to perform numerical simulations during or immediately after emergency situations, typically within a few minutes to a few hours. Complex edge-to-end UC workflows coordinate the execution of multiple model realizations to account for input and model uncertainties and can provide decision-makers with numerical estimates of the outcomes of emergency scenarios, such as earthquakes addressed by UCIS4EQ. UCIS4EQ is being driven toward operational maturity thanks to the technological and scientific developments within the eFlows4HPC project. Based on containerised micorservices, this workflow is fully orchestrated by the PyCOMPSs workflow manager to automatically prepare and manage physics-based deterministic simulation suites for rapid synthetic results. Through pre-computed and on-the-fly simulations, UCIS4EQ delivers estimates of relevant ground motion parameters, such as peak ground velocity, peak ground acceleration, or shaking duration, with very high spatial resolution. The physics-based engine includes pre-trained Machine Learning (ML) models fed with pre-computed simulation databases, as well as deterministic 3D simulations on demand, providing results in minutes and hours, respectively. The combined results, when well-calibrated, could lead to a new generation of ground shaking maps that complement GMPEs for rapid hazard assessment.To demonstrate the potential use of UC in seismology,  in this work we show the UCIS4EQ simulation of the M7.1 Puebla earthquake that occurred in central Mexico on the 19th of September 2017. With a hypocentre at 18.40ºN, 98.72ºW and 57 km depth, the Puebla earthquake was located about 150 km southeast from Mexico City. Identified as a severe event (VIII) in the Modified Mercalli Intensity scale, it resulted in a total of 370 killed and around 6000 injured, as well as structural damages, downed telephone lines, and ruptured gas mains.