Environmental and Earth Sciences

Abstract: Global terrestrial water storage change (TWSC) induces hydrological loading, a core driver of nonlinear deformations in GNSS benchmark coordinate time series. High-precision hydrological load models are essential for refining the Terrestrial Reference Frame (TRF) and investigating global climate change mechanisms. To address GRACE's coarse spatiotemporal resolution, discrepancies among reanalysis models, and the common reliance on single-source fusion without uncertainty quantification, we propose an LS-based scale-factor fusion scheme. Integrating GRACE Mascon data with the multi-model ACH-VCE product, we develop GHLW1.0. On a 1°×1° grid, LS determines optimal scale factors between GRACE and ACH-VCE, calibrating GRACE TWSC and fusing with ACH-VCE to produce the GHLW1.0 dataset (2000–2016). Multi-dimensional validation shows GHLW1.0 matches GRACE Mascon in linear trend, RMS of temporal signals, seasonal amplitude, and phase lag. Its phase difference relative to GRACE is ~15 days, substantially better than ACH-VCE's ~30 days, and captures finer spatial details. Applying GHLW1.0-derived vertical displacements to correct 300 GNSS stations, over 90% show correlation >0.7 between modeled and observed. Average correction efficiency is 76%, peaking at 79% (3% above ACH-VCE), with only 5% fluctuation across tests, indicating superior stability. Our LS fusion strategy compensates single-source deficiencies, enhancing TWSC retrieval and GNSS correction, and offers a novel pathway for high-precision stable hydrological load models. Future work will use Singular Spectrum Analysis to decompose homogeneous signals and optimize performance.

Abstract: Numerous landslides appeared in the region of Atsuma (Hokkaido, Japan) as a result of the 2018 Hokkaido Eastern Iburi Earthquake. Despite their devastating consequences, the emergence of mass movements may provide a unique opportunity to gain insight into specific chapters of Earth’s history by exposing new natural outcrops and revealing rock strata. In the region, geological formations, including the studied Middle Miocene Kawabata Formation, composed primarily of sedimentary rocks, reflect various deep-sea environments, especially the continental slope and basin plain of a foreland basin. For such a reason, the exposed bedding plane consisting of polygonal features in an outcrop formed at the scarp of a landslide aroused interest. Mud cracks or desiccation marks often form in the tidal zone due to exposure to the subaerial environment, but not in the aforementioned deep-sea facies. An additional series of evidence of wet and dry cycles in a near-shore (coastal) environment was revealed, such as limonite grain coatings and hypocoatings, and biotite exfoliation. Based on that evidence, a new Middle Miocene facies, a newly discovered stratigraphic member, was proposed in the Kawabata Formation, indicating a tidal palaeoenvironment.

Abstract: Oil-based mud filtrate (OBMF) invasion significantly alters the petrophysical response of nuclear magnetic resonance (NMR) logging, severely compromising the accuracy of reservoir fluid identification and petrophysical evaluation. However, the NMR relaxation behavior of OBMF under elevated temperatures (up to 100 °C) and low-frequency (< 2MHz) conditions remains poorly understood. In this study, temperature-dependent NMR experiments were conducted from 30°C to 100°C at a fixed frequency of 21MHz, while frequency-dependent experiments were performed from 1 MHz to 21MHz at 30°C. Using combined analysis of T₂ spectra and T₂-T₁ two-dimensional spectra, the effects of temperature and magnetic field frequency on the relaxation characteristics of OBMF were investigated under the conditions of this study. The results show that increasing temperature shifts the T₂ distribution toward longer relaxation times, increases T₁ values, and decreases the T₁/T₂ ratio. In contrast, decreasing frequency leads to prolonged T₂ relaxation times, shortened T₁ relaxation times, and a decreased T₁/T₂ ratio. Based on these experimental findings, a dual-parameter model incorporating both temperature and frequency was established for OBMF. The proposed model serves as a theoretical reference for the analysis and correction of NMR logging data acquired under oil-based mud invasion conditions.

Abstract: Distributed acoustic sensing (DAS) deployed in submarine telecom cables is bound to revolutionize the earthquake monitoring routine currently performed by seismic network operators, particularly in domains where most of seismic activity is originated offshore. In this work we analyze one year DAS data recorded on a submarine telecommunication cable joining the Islands of Faial and Flores in the Azores, an area where seismic crisis of volcano-tectonic origin are frequent. We explore whether spatially decimated channels can be added to the operation routine without major changes. During the DAS operation the land network recorded 368 local and regional earthquakes. The best of these events were jointly analyzed and earthquake parameters were compared between original locations and adding DAS picks. Despite the larger picking uncertainty on DAS channels, adding P and S or S-wave picks only from DAS data showed a considerable improvement on earthquake parameters, reducing the error ellipse area and the focal depth uncertainty. These results demonstrate that in domains where offshore seismicity is a concern and submarine telecom cables are available, integrating DAS channels into the routine operation of seismic networks considerably improve the accuracy earthquake parameter estimation. A procedure to accomplish these results is presented.

Abstract: Olivine, as (Mg, Fe)2SiO4 solid solution, governs the plastic flow of the Earth's upper mantle. While extensive studies exist on natural olivine-rich rocks, the rheology of its Mg-end member, forsterite (Fo), remains less constrained, particularly for diffusion creep. Here we synthesize high-purity (≥98 vol.%), iron-free forsterite aggregates via pressureless sintering and perform axial compression experiments in a high-stress-precision Paterson gas-medium apparatus at 300 MPa, temperatures of 1423–1523 K, and differential stresses of 50–380 MPa. Our results reveal a stress exponent n = 1.0 ± 0.08, an activation energy Q = 365 ± 22.7 kJ/mol, and a grain size exponent p = 2.9 ± 0.23, demonstrating that forsterite deforms by diffusion creep under these conditions. The grain size exponent, close to the theoretical value of 3 for Coble creep, indicates that grain boundary diffusion is the rate-controlling mechanism. Compared to previous studies on forsterite and natural olivine, our flow law shows good agreement with the activation energy for olivine diffusion creep but provides a significantly better-constrained grain size exponent. Critically, because our samples are chemically synthesized and iron-free, and lack the trace impurities that facilitate defect generation in natural olivine, they exhibit higher strength than natural Fe-bearing olivine. Our flow law therefore defines the Mg-end member for the olivine solid solution system and represents the viscosity upper bound for olivine-dominated mantle rocks deformed dominantly by diffusion creep. These findings not only fill a critical gap in the rheological data for the olivine solid solution end-members but also provide a robust basis for modeling viscosity variations in the upper mantle as functions of grain size, temperature, and iron content.

Abstract: Two breakwaters were constructed between 1959 and 1961 by the U.S. Army Corps of Engineers to form a harbor within Half Moon Bay on the central California coast. Prior to construction, the bay had a smooth hook-shaped or spiral form with a shoreline in equilibrium with waves refracted around a resistant point. Following breakwater completion, wave energy that had previously been dissipated along the equilibrium shoreline of the bay was concentrated at the downcoast end of the breakwater against the low weak bluffs. The original very low (~8 cm/year) bluff recession rates increased rapidly to as much as 2 m/year which led to the destruction of a county road and wastewater transmission line and began to threaten a state highway and a group of homes. Bluff erosion has progressed as far as 1.4 km downcoast which has led to rock revetment placement to protect the highway and homes. Breakwater planning also underestimated the potential for waves to enter the gap between the two breakwaters, so a dogleg extension had to be constructed. This also failed to reduce wave action, which led to construction of an additional set of breakwaters within the harbor to protect moored boats.

Abstract: The identification and delineation of subsurface resistive anomalies beneath sedimentary cover remain challenging for the magnetotelluric (MT) method. In this study, we compared the attenuation behavior of electromagnetic (EM) fields and their response characteristics under surface and/or subsurface observation configurations using both synthetic and field data. The synthetic results show that the conductive cover layer substantially suppresses the EM responses of the subsurface high resistivity body, producing only weak response perturbations at surface stations. In contrast, the response amplitudes recorded at underground stations are enhanced, indicating that underground EM observations provide advantages in resolving subsurface resistive anomalies and constraining their geometric boundaries. The results further reveal distinct attenuation behaviors of the electric and magnetic fields, with the electric field being more sensitive to variations in the bulk conductivity of the sedimentary layer. Furthermore, one-dimensional Bayesian probabilistic inversions of both synthetic and field datasets indicate that underground observations provide more robust and reliable estimates of the resistivity structure. These findings suggest that further exploration of deep underground observations and the deployment of high sensitivity quantum EM sensors have considerable potential for detecting and characterizing weak EM responses from resistive targets in sedimentary environments, while also improving the reliability of inversion results and reducing their uncertainty.

Abstract: To characterise the fracture network geometry of a fluid reservoir, fundamental parameters are used in a DFN simulation algorithm. However, evaluating the hydrodynamic behaviour of such rock bodies also requires apertures of individual fractures. Aperture is usually not treated as an independent variable; rather, it is derived from length. A common approach is a linear relationship, a = A*L, where A is the aperture coefficient. The fracture’s free volume varies with the aperture coefficient, which influences the modelled fractured porosity and permeability. Since post-tectonic fluid-rock interactions can considerably alter the original apertures, the relationship between fracture length and aperture may vary across a reservoir, complicating hydrodynamic modelling. Therefore, from a hydrodynamic perspective, the hydraulic aperture should be used instead of the physical aperture. In this paper, transmissivity data and DFN models are analysed simultaneously to estimate reliable aperture coefficients. The method is demonstrated using the fractured Mórágy Granite body in SW Hungary. In the context of the radioactive waste depository project, numerous wells penetrated the fractured granite. Transmissivity data and DFN models from 238 intervals are used to calibrate aperture coefficient values. The associated porosity data are employed to construct a porosity log for each well, and analyse poro-perm diagrams.

Abstract: Timor is situated in the Lesser Sunda chain of islands in the non-volcanic outer Banda Arc of the Australia–Southeast Asia orogen. Diachronous collision of the irregular passive margin of Australia with the detached margin of SE Asia in the Miocene produced an assemblage of nappes, mélanges and metamorphic terranes that characterise the complex geology of Timor. This article has been developed from a keynote presentation delivered at the 6th International Geoscience Conference of the Institute of Geosciences of Timor-Leste (IGTL), held in Dili in February 2026. In keeping with that format, the paper is a synthesis and interpretive review of Timor’s metamorphic terranes, and a fuller ex-planation of the concept of ‘splinter tectonics’ that was introduced. Field, petrographic and geochemical evidence show that the unique features of the Boi metamorphic massif on West Timor can be explained by a process whereby blocks and slices of deeply-buried upper-plate crust became entrained in the subduction channel and juxtaposed against hot forearc mantle before being extruded by buoyancy forces. The Boi Massif is therefore interpreted as a case study that provides new insights into the tectonic evolution of the Banda Arc and possible processes operating within convergent margin systems elsewhere.

Abstract: This study presents a 3D geological model and structural interpretation of the Masa Valverde volcanogenic massive sulphide (VMS) deposit in the Iberian Pyrite Belt. The deposit is hosted by felsic porphyritic volcanic rocks, volcanic tuffs and black shales. A 3D geological model of the orebodies and host rocks, constructed from 145 drillcore logs, allowed us to build 16 cross-sections spaced 100 m apart, and constrain the mineralisation geometry and its structural evolution. Mineralization formed during Early Carboniferous transtensional tectonics within an extensional basin, where an extensional duplex structure controlled the development of the primary massive sulfide body and its associated stockwork. Subsequent counterclockwise rotation of the principal stress axes reactivated extensional faults as reverse faults during tectonic inversion. This deformation strongly modified the VMS system through buttressing, generating extensive open spaces and promoting brecciation and recrystallization of both the stockwork and massive sulfides. These processes produced a new paragenesis dominated by chalcopyrite and sphalerite, with minor galena among other minerals, which cemented the breccias, partially replaced earlier mineral assemblages, and filled open fractures. The resulting Cu-Zn enrichment, spatially associated with buttressed zones, provides new insights into ore remobilization with direct implications for the development of the ongoing underground mine.

Abstract: Rock physics model provides an essential theoretical tool to quantify the impacts of reservoir physical parameters (porosity, water saturation, etc.) on seismic elastic properties including P- wave velocity and S-wave velocity. As a core module for deriving physical properties through joint well-seismic inversion, rock physics modeling accuracy directly determines the reliability of reservoir property prediction. Simultaneous characterization of pores and oriented fractures is required to refine modeling precision, yet the resulting excessive model parameters severely limit applications to field seismic data. To address the critical issue of applying pore and fracture anisotropic rock physics models to azimuthal seismic interpretation, this work decouples pores and oriented fractures during modeling. We postulate that pore variations control the model’s isotropic elastic properties, whereas oriented fracture characteristics dominate anisotropic parameters. Well-log data are utilized to invert key modeling parameters (matrix mineral elastic moduli, fracture porosity, etc.) for model correction. The corrected rock physics model is further coupled with the Rüger reflectivity equation to analyze how porosity and fracture azimuth alter seismic reflection coefficients and synthetic seismic records. The presented anisotropic rock physics correction method via parameter inversion greatly elevates modeling accuracy. Rock-physics-based analysis of azimuthal seismic reflection shows promising prospects for widespread use in fractured reservoir characterization.

Abstract: The scarcity of high-quality Paleozoic paleomagnetic data from the South China Block (SCB) has rendered the kinematic history of its rifting and drifting from Gondwana highly debated, consequently leaving the timing of opening and subsequent spreading of the Ailaoshan-Songma eastern Paleo-Tethys Ocean (ASePTO) poorly constrained. Here we report new paleomagnetic results from Givetian (~385 Ma) limestones of Dushan County, Guizhou, yielding a characteristic remanent magnetization (ChRM-B). Although the ChRM-B shows predominantly single polarity and an inconclusive fold test, multiple lines of evidence support its primary origin: (i) the corresponding paleomagnetic pole (29.5°N, 229.8°E; dp/dm = 2.0°/3.8°) differs substantially from all post-Middle Devonian SCB poles; (ii) rock magnetic analyses combined with high-resolution transmission electron mi-croscopy indicate that nanoscale detrital magnetite and maghemite are the main rema-nence carriers; and (iii) statistical consistency between the 7 site-mean directions of the ChRM-B and 34 coeval site-mean directions from the published Yuntaiguan Formation red bed records in western Hunan. In the light of the compatible ages and geological settings of the sampling strata from the two sampling areas, the two datasets were combined to derive a robust Middle Devonian paleomagnetic pole for the SCB. The merged dataset (41 sites) yields mean directions of D_g/I_g = 37.2°/-18.9° (k_g = 46.4, α₉₅ = 3.3°) before and Ds/Is = 43.1°/-23.8° (k_s = 54.4, α₉₅ = 3.1°) after the tilt-correction with a B-class reversals test and a positive fold test. The new robust paleomagnetic pole for the SCB, at 33.2°N, 234.7°E with A₉₅ = 2.4° and reliability index R = 7, when integrated with other reliable paleomagnetic records, allow the construction of an updated apparent polar wander path (APWP) for the SCB. Comparison with synthetic APWP of Gondwana enables the reconstruction of the opening of the ASePTO at ~410-400 Ma, followed by the spreading of the ocean basin to a N-S width of ~1200 km by ~385 Ma.

Abstract: Quartz purity is essential for reliable optically stimulated luminescence (OSL) dating, yet the mineralogical evolution of sediment samples during extraction is rarely documented at each preparation stage. This study uses scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) to characterize two loess samples from the Urluia section, Dobrogea, Romania, across sixteen successive stages of a standard OSL quartz extraction protocol. Four compositional indices - the Quartz Purity Index (QPI), Feldspar Contamination Index (FCI), Heavy Mineral Index (HMI), and Carbonate Index (CI) - are introduced to quantify purification efficiency. Each preparation stage contributed differently: HCl treatment primarily removed carbonates, grain-size separation and density fractionation reduced heavy minerals by ~99%, and feldspar removal resulted from the combined effects of density separation and HF etching. Despite identical protocols, two samples collected from stratigraphically adjacent positions showed markedly different HF etching efficiencies, reaching ~94% and ~66% quartz purity, respectively. However, luminescence measurements showed similarly weak feldspar signals in both samples, with intensities substantially lower than the quartz OSL signal. These results demonstrate that purification efficiency cannot be assumed to be uniform across samples and highlight SEM-EDS as a practical quality-control tool for OSL sample preparation.

Abstract: The vibration response of a cracked ice shelf to tsunami wave forcing is studied. In particular, the tsunami induced calving events in the Sulzberger Ice Shelf in 2011 and 2022, is investigated. The time-domain response is reconstructed from the wave-frequency response, and the stress field is calculated to evaluate the crack-tip stress intensity. Assuming that crack growth is governed by the Paris Law, the fatigue growth constant for this ice shelf is estimated. This work is presented as a preliminary study demonstrating how these rare geophysical phenomena can be used to estimate critical material parameters.

Abstract: This study demonstrates the successful application of passive seismic interferometry, specifically through the autocorrelation function, to extract high-resolution P-wave reflections from seismic data acquired during hydraulic fracturing. This application demonstrates the efficacy of extracting high-resolution P-wave reflectivity using hydraulic fracturing-induced seismic noise, a previously underexplored source for exploration-scale imaging. Stacking these reflections allows the construction of seismic sections at zero offsets. Typically, this technique uses data based on environmental noise and earthquakes. However, this study used measurements obtained during hydraulic fracturing in the Potiguar Basin of Northeast Brazil. We applied a processing sequence that included the Gaussian Smoother Filter to generate a smoothed amplitude spectrum and to extract the best body-wave component of Green’s function. We whitened the spectrum to remove any unwanted effects from the sources. The resulting seismic sections were compared with seismic lines acquired near the study area and interpreted in light of the available geological information. The seismic images were constructed in 2D and projected into 3D, with reflectors exhibiting high resolution and lateral continuity. Deeper reflectors align well with available geological and geophysical data; however, validation of the shallowest boundaries remains limited by the absence of high-resolution reference data in this area. The estimated time depth reached 2s. Validation of the shallowest reflectors (< 500 m depth, corresponding to the Cenozoic cover and upper Jandaíra Formation) is limited by the absence of high-resolution geological data at the survey site. No shallow boreholes or outcrop transects are available to confirm the depth and continuity of these interfaces. Legacy active seismic lacks resolution above ≈300 m depth. Consequently, our interpretation of shallow reflectors relies on regional geological maps and extrapolation from nearby wells, introducing uncertainty. Future work should include shallow drilling or high-resolution GPR surveys to validate the uppermost 500 m of the autocorrelation sections. Additionally, the maximum penetration depth of the S-wave velocity model (approximately 180 m) is constrained by the short maximum offset (1,450 m), precluding integration with deeper autocorrelation-derived reflectivity. We calculated cross-correlations using two configurations—one with the longest available offset (1,450 m) and one within a single line—to obtain S-wave velocity models and determine the maximum penetration depth (approximately 180 m) achievable with the current acquisition geometry.

Abstract: Underground water hazards are among the most serious concealed threats to safe coal mine production, yet their accurate spatial localization remains challenging when relying on a single geophysical method. This study proposes a joint detection framework integrating the magnetotelluric (MT) method and the microtremor survey method (MSM), and applies it to the Shaping Coal Mine in Lianyuan City, Hunan Province, China. The MT method was used to image the resistivity structure of water-bearing bodies at depths of 50–500 m, while the MSM delineated the shear-wave velocity structure of shallow-to-middle strata (0–300 m). A comprehensive identification criterion based on the spatial superposition of "low resistivity + low velocity" anomalies was established. The MT results identified three key low-resistivity water-bearing structures within the coal-bearing Ceshui Formation, while the MSM revealed low-velocity anomalies associated with the Coal Seam No. 5 goaf and fault fracture zones. The two methods formed an effective overlapping detection zone at depths of 100–300 m, with anomalies distributed above the mined-out area and near the Sifangqiao reverse fault, showing strong correspondence with documented water seepage. Cross-validation between the two methods improved the identification accuracy of middle-deep water hazards to over 85%, providing reliable geophysical evidence for coal mine water hazard prevention and control.

Abstract: With the continuous increase in coal mining depth in China, concealed geological structures—such as collapse columns and faults—pose a severe threat to mine safety by inducing water inrush accidents. Mine DC resistivity methods exhibit high sensitivity to the water-bearing characteristics of geological bodies but suffer from limited resolution. In contrast, mine seismic exploration offers high resolution but shows weak responses to water-rich bodies. Single-method inversion inevitably faces the issue of solution non-uniqueness. This study aims to enhance the detection accuracy of concealed structures by implementing a joint seismic-electric inversion, leveraging the complementary advantages of both methods. For the DC resistivity component, a forward model was established using the finite element method with unstructured meshes, and inversion was performed using a least-squares algorithm. For seismic exploration, forward modeling utilized curved-ray tracing, and inversion was conducted via the LSQR algorithm. Cross-gradient constraints were incorporated into the joint inversion to establish a structurally coupled framework. Numerical simulation results indicate that while single-method inversions (DC or seismic) can preliminarily identify anomalies, they are limited by issues such as anomaly diffusion and false anomalies. In contrast, the joint in-version effectively constrains the spatial extent of anomalies, accurately characterizes the morphology and location of multiple anomalous bodies, fractures, and water-conducting fault channels, and significantly reduces solution non-uniqueness. This research provides a reliable methodology for the refined detection of concealed hazard-inducing structures, offering substantial practical value for ensuring coal mine safety.

Abstract: Generative modeling has become a practical prior family in geophysics, with score-based and diffusion models now used for seismic processing, inversion, subsurface monitoring, digital rock physics, well-log synthesis, and benchmark-driven reproducibility. Diffusion is best read as a restoration and posterior-sampling prior whose value depends on forward-model consistency, benchmark design, baseline coverage, and explicit uncertainty diagnostics rather than visual plausibility alone. The taxonomy links generated objects, model families, conditioning interfaces, physical coupling, and validation burden. Current evidence is strongest for seismic restoration and controlled posterior-sampling studies, and weakest for calibrated uncertainty in field-scale decisions. Scope is bounded to exploration and reservoir geophysics; ground-motion synthesis and electromagnetic, magnetotelluric, and potential-field methods are out of scope.

Abstract: Exploratory Data Analysis (EDA) has recently enabled the correction of several long standing misconceptions in geophysics, where a number of erroneous theories had been regarded as fundamental laws. These include revisions to the Gutenberg–Richter law, re evaluation of the Omori formula, improved visualisation of plate boundaries around Japan, and renewed prospects for earthquake prediction. To apply EDA effectively to one’s own data, a basic grounding in statistics and the ability to use a statistical software environment are essential. In this article, we introduce the use of R, an open source statistical computing platform, and demonstrate that conducting such analyses is both accessible and straightforward. Earthquake data were obtained from catalogues published by the Japan Meteorological Agency, and all computations were performed in R. The analyses show that modern statistical methods—particularly EDA combined with computational tools—substantially enhance the accuracy, interpretability, and visualisation of seismic data. Key earthquake related quantities are found to follow distinct statistical behaviours, including normal distributions of magnitudes, log normal distributions of released energy, and first order decay patterns with clear half lives in aftershock sequences. Enhanced three dimensional visualisation further clarifies the structural relationships among plate boundaries and seismic activity. Overall, the findings demonstrate that data driven and statistically rigorous approaches not only deepen our understanding of earthquake processes but also challenge several long standing empirical assumptions. This highlights the need for their re evaluation and provides a stronger foundation for future research, including potential advances in earthquake prediction.

Abstract: Concentric (ring-shaped) structures expressed in surface morphology and in potential-field data are widespread at the junction of the Tien Shan orogen and the Fergana Depression in Eastern Uzbekistan, yet their deep architecture and origin remain debated. Here we integrate regional gravity, aeromagnetic, and deep seismic sounding (DSS) data with radially averaged power-spectrum depth analysis, three-dimensional (3D) inversion, and geographic information system (GIS) mapping to reconstruct the crustal distribution of density and magnetic susceptibility to depths of about 25 km, and to test whether these structures are rooted endogenic features or surficial landforms. The 3D inversion resolves concentric low-density cores (density contrasts of 150–350 kg/m³) and magnetic susceptibilities of (1–8) × 10⁻³ SI that are spatially coincident with inferred Palaeozoic–Mesozoic magmatic centres and with intersections of deep-seated faults of the Talas–Fergana system. DSS profiles place the Conrad and Mohorovičić (Moho) discontinuities at 15–25 km and 35–55 km, respectively, and show that the concentric features extend coherently into the lower crust. The absence of shock-metamorphic indicators, together with smooth radial gradients and deep fault-controlled roots, excludes an impact origin and supports a tectono-magmatic model of mantle upwelling, magmatic differentiation, and repeated post-collisional fault reactivation. The results refine the regional geodynamic model and inform seismic-hazard and mineral-prospectivity assessment in Central Asia.