This paper presents a case study on the application of an electrical resistivity survey to detect a graphite ore body and identify its distribution in the Gapyeong area, Gyeonggi Province, South Korea. As securing a stable supply chain for graphite, a key material for the Fourth Industrial Revolution, has become crucial, the need for domestic resource exploration is growing. Graphite’s physical property of having much higher electrical conductivity than its surrounding host rock allows for the effective use of electrical/electromagnetic survey methods as exploration tools. In this study, a 3D electrical resistivity survey was conducted over a conductive anomaly in the Gapyeong area, which had been previously surveyed through a fixed-loop time-domain electromagnetic (FLTEM) survey. The acquired data was processed through 3D inversion to visualize the subsurface electrical resistivity distribution, revealing a distinct low-resistivity anomaly developing in a north-south direction. Drilling results from the previous survey confirmed that this low-resistivity zone corresponds to a high-grade graphite ore body, thus demonstrating that electrical resistivity surveys are highly effective for exploring domestic graphite deposits.
Rock discontinuity roughness is a key morphological characteristic that reflects geological history and strongly influences the mechanical and hydraulic behavior of rock masses. Although the size effect of roughness has long been recognized, previous studies have reported inconsistent and even contradictory trends. In this study, the roughness size effect was investigated quantitatively and comprehensively using two natural granite joint surfaces. A total of 120 two-dimensional profiles were extracted, and wavelet decomposition was applied to separate each profile into primary roughness (waviness) and secondary roughness (unevenness). The size effect was then analyzed using four roughness parameters with different characteristics: the root mean square of the first derivative of the profile (Z2), the center line average (CLA), the fractal dimension (D), and the amplitude parameter (A). To secure enough and stable samples, a global search sampling method was adopted. The results showed that the size effect varied markedly depending on the selected roughness parameter. Z2 and D exhibited diverse trends, including positive, negative, no, and inconsistent effects, whereas CLA consistently showed a positive effect. The results further indicated that the relative contributions of waviness and unevenness influenced the type of size effect, particularly for the fractal dimension: profiles dominated by secondary roughness tended to show positive effects, whereas those dominated by primary roughness were more likely to show a negative effect. However, the group differences were not statistically significant so that the observed tendency should be regard as preliminary. In addition, the sampling method significantly affected the overall trends, especially at small sampling sizes where local heterogeneity became more influential. These findings indicate that the roughness size effect cannot be generalized as a single universal trend, but should instead be interpreted in relation to surface morphology and experimental factors.
Methane hydrate samples were collected during the KS-25-8 cruise from three sites in the back-arc basin located offshore western Honshu, Japan: NW Torigakubi Spur (TRKB), NE Rokko-Oki Uplift Zone (ROUZ), and SW Oki Ridge (OR). Massive methane hydrates recovered from piston cores were analyzed for gas compositions and isotope ratios (δ13C-CH4 and 3He/4He) to investigate methane origin and contributions of mantle and crustal fluids. Gas compositions are dominated by methane with contributions from ethane and higher hydrocarbons. Carbon isotope compositions of methane (δ13C-CH4 = − 69.8‰ to − 37.5‰) indicate that thermogenic methane occurs at the NW TRKB, whereas microbial methane predominates in the NE ROUZ and SW OR. Methane is predominantly derived from shallow microbial and thermogenic sources, whereas mantle-derived methane contributes less than 0.1
The Main Himalayan Thrust (MHT) is the principal seismogenic structure beneath Nepal, yet the extent to which catalog-scale seismicity reflects along-strike segmentation remains uncertain. We analyze an International Seismological Centre (ISC) earthquake catalog, queried through FDSN services, covering 1990–2025 within 80–89°E and 26–31°N, retaining events with reported depths of 0–50 km and preferred magnitudes of M ≥ 3.0. The filtered catalog contains 3,864 events. Frequency-magnitude diagnostics indicate Mc ≈ 3.55 from the maximum-curvature method and Mc ≈ 3.70 from the 95
This study presents the first documented occurrence of the Fe-rich clay minerals berthierine and chamosite in continental siliciclastic sandstones of the Oligocene Mugrosa Formation, within the Nuevo Mundo Syncline of the Middle Magdalena Basin (MMB), Colombia. These hydrocarbon-saturated sandstones, comprising over 70
Utilizing strong-motion data recorded by seismic stations to study the correlation characteristics between ground motion parameters can provide fundamental references for ground motion parameter selection and seismic risk assessment, which has important theoretical and practical significance. This study selected near-field acceleration records from several moderate-to-strong earthquakes in western China since 2008, focused on 27 ground motion parameters including peak ground acceleration (PGA), peak ground velocity (PGV), spectral acceleration (Sa(T), T = 0.1–5.0 s, 21 period points), Arias intensity (AriasIM), spectrum intensity (SI), cumulative absolute velocity (CAV), and 5–95
Groundwater is a vital natural resource, essential for domestic, agricultural, and industrial purposes. The demand for groundwater has significantly risen due to population growth, modern irrigation techniques, and increased industrial usage. The present study utilizes Remote Sensing Geographic Information System (GIS) techniques to analyze the morphometric parameters for understanding the hydrogeological conditions and several thematic layers like geomorphology, rainfall, drainage density, lineament density, soil, geology, and slope using Analytical Hierarchical Process (AHP) method to depict the prospective groundwater potential within the Luni River Basin (LRB). The morphometric parameters (Linear, areal, relief, shape Hypsometric) collectively paint a picture that LRB is a fifth-order basin and persists a dendritic (tree-like) drainage pattern that is favourable for the infiltration of groundwater. Morphometric parameters provide a primary understanding of the basin’s hydro-geomorphic framework. So, detailed hydrogeological studies integrating with the thematic layers added more significance to groundwater potential mapping. Using the weighted overlay analysis using AHP method, three distinct groundwater potential regimes are demarcated within the Luni River basin, with the western sector exhibiting a notably diminished degree of groundwater potential while the eastern sector manifests a substantially elevated groundwater potential capacity. This variation is indicative of contrasting hydrogeological conditions, likely influenced by geological, geomorphological, and climatic factors that warrant further investigation and detailed exploration for comprehensive groundwater resource management within the basin.
The accurate detection of co-occurring metal resources in known deposits has long been a technical challenge. This is particularly true for the evaluation of a newly identified type of altered rock-type Nb-Ta mineralization within Banded Iron Formation (BIF)-type iron deposits, which represents a critical research gap that must be addressed. In view of this, this study selects the altered rock-type Nb-Ta mineralization in Qidashan iron deposit as the research object. The physical properties of the iron ore bodies, host rocks, greisenized altered rock-type Nb-Ta ore, and chloritized altered rock-type Nb-Ta ore were measured and analyzed. An integrated geophysical approach, combining ground high-precision magnetic and electrical resistivity tomography (ERT) methods, was employed to identify and locate the altered rock-type Nb-Ta mineralization within the BIF-type iron deposits. The results demonstrate that the integrated geophysical method, combining magnetic and ERT methods, can not only accurately delineate the lateral extent of the altered rock-type Nb-Ta mineralization but also effectively characterize its vertical extension and variation at depth. The altered rock-type Nb-Ta mineralized zone in the Qidashan iron deposit measures over 200 m in length, approximately 150 m in thickness, and extends over 60 m in depth. This geophysical methodology establishes a viable strategy for detecting and assessing altered rock-type Nb-Ta mineralization in BIF-type iron deposits, thereby facilitating the concurrent exploitation of both the iron ore and the altered rock-type Nb-Ta ore.
This study focuses on a large rainfall-induced Lishi loess landslide in the Yuwa area of Lingbao City, Henan Province. A three-dimensional PFC (Particle Flow Code) 3D discrete element model was used to simulate the entire process from landslide initiation to failure, taking into account the reduction of loess shear strength due to heavy rainfall and the coupling effects at the soil-rock interface. The simulation results show that the slip of the underlying bedrock provides traction and dynamically amplifies the motion of the overlying loess slide mass. The slip zone cuts through the soil-rock contact, forming a composite slip surface. The landslide’s failure mode is characterized by a combined process: the crest of the slope slides first, the moving bedrock exerts a traction force, and the front (toe) of the slide is pushed forward. The displacement evolution of the landslide progresses through four stages—initial slight movement, accelerated sliding, rapid (catastrophic) sliding, and deceleration to stabilization. In the x-direction (horizontal), the slope crest experienced about 35 m of displacement and the toe about 30 m. The y-direction displacement was small; movement was first toward the right then toward the left, eventually becoming synchronized. Vertical deformation (z-direction) included up to 12.5 m of subsidence at the slope crest and about 5 m of uplift at the toe, exhibiting a typical “shovel-shaped” deformation pattern. At the microscale, the coordination number of the granular soil structure fluctuated between 4.05 and 6.38. The coordination number at the slope crest dropped to as low as 4.05, indicating a loose particle structure prone to instability, whereas at the slope toe it remained higher (up to 6.38), reflecting a dense, load-bearing structure. The simulated deformations agree closely with field-monitored deformations (R² > 0.85), confirming the reliability of the model. Based on these findings, a comprehensive mitigation approach combining anti-slide reinforcement with improved drainage is proposed, along with prevention and control measures that integrate monitoring feedback to inform early warning and adaptive management.
Hydrogen isotopes (δD) in basaltic magmas record a wide range of processes controlling the distribution and cycling of water in the Earth’s interior, from planetary accretion and core formation to subduction recycling and shallow modification. This review synthesizes the hydrogen isotope systematics of glasses and olivine-hosted melt inclusions from mid-ocean ridges, ocean islands, back-arc basins, and arc settings, evaluating the processes that govern δD variability. Compilation of global datasets shows that regional δD variability reflects isotopically distinct source components: the depleted mantle is characterized by low despite heterogeneous δD values, while slab-derived fluids shift mantle domains toward higher δD values. The δD values of deeply subducted materials depend strongly on the extent of dehydration, with incompletely dehydrated slabs retaining elevated δD and extensively dehydrated residues developing anomalously low δD values. Extremely low δD values observed in some ocean island basalts further suggest the presence of highly D-depleted hydrogen in deep mantle sources, possibly involving core–mantle boundary exchange. In addition, shallow processes including magmatic degassing, secondary hydration, assimilation, and diffusive hydrogen exchange in melt inclusions can significantly modify primary δD values and produce trends that overlap with source-driven variability. Robust interpretation of mantle hydrogen isotopes therefore requires integration with complementary geochemical tracers such as radiogenic isotopes, noble gas systematics, and other volatile proxies. Comprehensively, these observations indicate that the Earth’s mantle is considerably heterogeneous in hydrogen isotope composition, reflecting the sensitivity of δD to processes operating across Earth’s history, from planetary accretion to present-day deep water cycle.
In recent probabilistic seismic hazard analyses (PSHA), the logic-tree framework has become a widely used approach to systematically represent epistemic uncertainties associated with the input models and parameters. While numerous studies have examined the fundamental principles behind constructing and organizing logic trees, none have provided a detailed and explicit formulation for the computation of end-branch weights and seismic hazards within the overall framework. This limitation becomes particularly important when multiple seismic sources contribute to the total hazard at a site, making the aggregation of epistemic uncertainties more complex. To address this gap, the present study introduces a clear and mathematically rigorous formulation for the calculation of end branch weights, the evaluation of hazard contributions from multiple sources, and the derivation of the combined seismic hazard at a given site. The proposed formulation aims to provide both transparency and consistency in the representation and computation of epistemic uncertainties in PSHA studies.
Natural fractures play a crucial role in controlling shale reservoir productivity, emphasizing the need for thorough characterization and predictive modeling to improve hydrocarbon extraction efficiency. In this study, a comprehensive workflow integrating borehole core observations, imaging logging interpretations, and data-driven predictive modeling was employed to investigate natural fracture systems in the Longmaxi Formation shale gas reservoir located in the Luzhou area of the southern Sichuan Basin. First, the mechanical types, filling degree, and occurrence characteristics of natural fractures were quantitatively characterized. Subsequently, leveraging these insights, a neural network model trained on conventional logging data was developed to predict fracture intensity in individual wells, demonstrating broad applicability where imaging log data are limited. Furthermore, correlation analysis identified tectonic activity, curvature attributes, and rock mineral composition as the primary factors influencing fracture development. Finally, by integrating multi-attribute fracture intensity probability volumes (with spatial constraints) and statistical analyses of dip-azimuth data, a 3D multiscale fracture model was constructed, which achieved a prediction error rate of 7.32–18.18
This study develops a high-resolution groundwater potential map for the Andijan Region in the eastern Fergana Valley, Uzbekistan, by integrating the probabilistic frequency ratio (FR) method with a long short-term memory (LSTM) neural network. Eleven hydrogeomorphic, lithological, and land-surface variables—Channel Network Base Level, Closed Depressions, Cross-Sectional Curvature, DEM, Downslope Curvature, LS factor, Topographic Wetness Index, Valley Depth, Geology, Soil, and Land Cover—were derived from 12.5 m ALOS PALSAR topographic data, Sentinel imagery, and national geodatabases. FR analysis quantified the contribution of each factor to observed well yields, generating factor-specific weights and using gridded predictors as inputs to the LSTM to capture nonlinear spatial interactions. Validation against an independent dataset comprising 61 surveyed production wells showed an improvement in the area under the receiver operating characteristic curve from 75.60
The present research presents an updated seismic hazard map for the Gujarat region, regarded to be among the most earthquake-prone intraplate regions globally. The region experienced two catastrophic earthquakes with magnitudes over MW 7 (1819 Allah Bund earthquake; Mw 7.8 and 2001 Bhuj earthquake; MW 7.7) in less than the span of 182 years, along with several moderate events that resulted in numerous casualties and major financial losses to the state. The high rate of industrial development and upcoming new mega and smart cities projects demand an updated hazard map of the region to mitigate the seismic hazards. The study area is categorized into seven seismogenic zones based on seismotectonic features and local geology. A probabilistic seismic hazard assessment (PSHA) map was developed using regional and global attenuation equations in accordance with the Classical Cornell methodology. Peak Ground Acceleration (PGA) and Spectral Acceleration (SA) were assessed at the NEHRP soil class B/C boundary and at the surface level, considering probabilities of exceedance of 2
In 2023, a commercial superconducting gravimeter (iGrav S/N 055) was installed and became operational at the Gravity Continuous Observation Station (GCOS) of the Space Geodetic Observatory in Sejong, South Korea, marking a significant advancement in high-precision gravity monitoring. This installation enables continuous acquisition of high-quality gravity data, facilitating precise analysis of temporal gravity variations. To ensure stable operation and effective data processing, strategies were developed with consideration of local environmental conditions. These include the use of advanced frequency-domain techniques for noise reduction and the construction of a regional tidal model based on consistent and precise gravity observations. This study presents the methodology for accurate gravity monitoring using superconducting gravimeters, the approach for establishing a unified reference frame through future integration with VLBI, and potential geodetic applications. These efforts aim to improve gravity data reliability and enable meaningful comparisons with space geodetic observations. The station is expected to serve as a fundamental reference point for geodetic research, contributing to regional geoid modeling and the development of vertical datum systems. Furthermore, by linking gravity data with VLBI and GNSS, this research lays the groundwork for understanding Earth’s dynamic processes such as crustal deformation, tectonic activity, and environmental changes. The integration of these technologies offers valuable insights into Earth system dynamics and supports the advancement of modern geodesy.
In rough-walled fractures, solute dispersion is controlled by flow heterogeneity: transverse heterogeneity across the fracture aperture promotes Taylor dispersion (∝ v²), whereas longitudinal heterogeneity along the fracture plane promotes macrodispersion (∝ v, where v is the mean velocity). Two widely used models for the longitudinal dispersion coefficient, the power-law relation (DL, with DL ∝ vn, 1 ≤ n ≤ 2) and the linear-quadratic relation (DL ∝ v + v2), reflect the interplay between macrodispersion and Taylor dispersion but have been evaluated mainly under low Reynolds numbers (Re ≪ 1). A critical knowledge gap remains as to which model more accurately captures solute dispersion at higher velocities. To address this unresolved issue, this study employs high-resolution microscopic Particle Image Velocimetry to directly measure spatial variations in fluid velocity within a rough-walled rock fracture over Re = 0.1, 1, 10, and 30. At Re ≤ 1, longitudinal and transverse velocity gradients scaled nearly linearly with Re, indicating comparable contributions to solute dispersion and supporting the applicability of both dispersion models. At Re = 10, eddy onset initiated divergence between the two gradients, and by Re = 30, transverse gradients steepened markedly, exceeding longitudinal values by nearly an order of magnitude, confirming a transition toward Taylor-dominated dispersion. This mechanistic shift highlights the limitation of the power-law formulation, which cannot capture regime transitions, and points to the linear-quadratic model as a more realistic representation of solute dispersion in rough-walled fractures.
The Bangkok metropolitan area has experienced land subsidence in the past, primarily associated with groundwater overextraction. Following the implementation of groundwater management policies, subsidence rates have decreased, and several studies have reported localized uplift in some areas. However, studies that examine the long-term spatiotemporal evolution of surface deformation remain limited. This study analyzes the spatiotemporal characteristics of land surface deformation in the BMA using multi-temporal InSAR observations derived from ALOS PALSAR (2007–2010) and Sentinel-1 (2014–2024). Time-series InSAR processing was performed to estimate surface displacement, and the results were validated using independent GNSS measurements. Groundwater level data were further incorporated to examine their temporal relationship with surface deformation. The results show that during 2007–2010, surface uplift of + 0.5 cm/year occurred in central Bangkok, and the deformation pattern changes from uplift to subsidence with increasing distance from central Bangkok. The later period (2014–2024) is characterized by weak but persistent subsidence across most of the study area, with an average rate of − 0.3 cm/year. During the period 2007–2010, groundwater levels increased at a rate of approximately + 1.2 m/year, accompanied by surface uplift. Despite gradual increases in groundwater levels, subsidence continued during the later period, indicating that groundwater recovery does not necessarily lead to surface uplift. This behavior suggests that surface deformation is influenced not only by groundwater level changes but also by additional processes, such as delayed consolidation of compressible aquitards and irreversible compaction. By integrating multi-sensor InSAR datasets, this study extends the observation period and enables the comparison of deformation characteristics across different time intervals. The results highlight the importance of long-term monitoring for understanding deformation trends and could provide useful information for future subsidence assessment and groundwater management in similar environments.
The occurrence of harmful algal blooms in Jinyang Reservoir, South Korea, has raised public concern, particularly among residents who depend on the reservoir as a drinking water source. To address these concerns, the present study investigated the total P (TP) release behavior of sediments from Jinyang Reservoir and its tributaries, namely the Deokcheon and Gyeongho Rivers, focusing on the roles of indigenous microbial communities and sedimentary redox processes. Sediment analyses revealed distinct microbial profiles across the investigated sites: iron-oxidizing bacteria dominated in the Jinyang Reservoir sediments, while sulfate-reducing bacteria were more prevalent in the Deokcheon and Gyeongho River sediments. These microbial differences may have influenced sediment redox conditions and indirectly affected Fe-associated P mobilization. Elevated pH further enhanced TP release, underscoring the contribution of alkaline conditions to P mobilization. Mitigation experiments demonstrated that treatments with an oxygen-releasing agent (CaO2) and loess particles effectively suppressed TP release. However, additional studies are required to assess their long-term efficacy and ecological consequences. Overall, our findings offer valuable insights for developing eutrophication control measures in Jinyang Reservoir and its tributaries. Implementing targeted interventions based on these results may help reduce nutrient loading and alleviate eutrophication risks in reservoir systems.
The newly discovered Mirae-2 vent field, located at a depth of 3,300 m on the slow spreading Central Indian Ridge (14–15°S), is characterized as a high-temperature vent field. Samples were collected using remotely operated vehicle ROPOS to investigate the mineralogical, geochemical, and biological characteristics of the uppermost layer of the hydrothermal sediment and the microbial mat around the high-temperature Mirae-2 vent site. The results reveal that the Mirae-2 vent field sediments are iron-enriched but exhibit significant depletion of sulfur and other metals. The mineral assemblages indicate abundance of iron-oxides/oxyhydroxides and minor components of calcium carbonates and feldspar in sediments, while vent chimney structures are abundant in metal sulfides. Overall, the geochemical results indicate that the hydrothermal sediment and the microbial mat are significantly affected by hydrothermal processes, rather than being of lithogenic or pelagic origin. The microbial diversity within the hydrothermal sediment and the microbial mat is predominantly composed of Gammaproteobacteria and Alphaproteobacteria, which are frequently observed representative microbes in hydrothermal vent systems. The low concentrations of metals (except for iron) and sulfur relative to other hydrothermal vent fields may be attributed to local current effects and sub-seafloor mixing of the hydrothermal fluid with ambient seawater. The discovery of a new vent field, particularly with its sulfur-depleted hydrothermal sediments, provides valuable insights into the characteristics and ecological dynamics of hydrothermal systems in the Indian Ocean.
The northern Alxa region occupies the crucial location for better understanding the tectonic evolution of the Central Asian Orogenic Belt. While numerous studies have focused on the final closure of the Paleo-Asian Ocean, the deep crustal structure is still poorly constrained. Here, a total of 27 magnetotelluric (MT) sites were measured along a 70 km long, NNE-SSW-trending profile to investigate the deep electrical structure beneath the northern Alxa region. The resistivity model obtained from 3-D inversion reveals an unexpectedly heterogeneous crustal structure. The northern segment exhibits a high resistivity anomaly, providing geophysical constraint for the Precambrian crystalline basement. In contrast, the southern segment is characterized by sub-horizontal intra-crustal high conductive anomaly at 15 km, sandwiched between the high resistive upper crust and moderate resistive lower crust. Here, we interpret the intra-crustal conductor as the result of saline fluids. Based on the Hashin-Strikman upper bound, we estimate that a saline fluid fraction of 0.1
