Hasil untuk "Geology"

Kaan Çökerim, Henryk Dobslaw, Kyriakos Balidakis et al.

Abstract Daily displacement time series from Global Navigation Satellite Systems (GNSS) are frequently used to study deformations of the Earth’s surface due to a wide range of different geophysical processes. The recorded deformations result from tectonic activity or non-tectonic processes like volcanism, groundwater fluctuations and atmospheric loading. In addition, local disturbances of the antenna (e.g., snow cover, thermoelastic effects of the monumentation) and artifacts from GNSS processing (e.g., draconitic signals) are sometimes prominently included in coordinate time series. We use a Temporal Convolution Network (TCN) to predict non-tectonic vertical GNSS displacements on a global scale from physics-based non-tidal loading products. We train our model on a global dataset with more than 11,000 GNSS stations from the Nevada Geodetic Laboratory, active from January 2002 until June 2024, and evaluate the performance against independent estimations. Across the hold-out dataset, our TCN derives non-tidal loading GNSS signatures that when compared to the non-tectonic GNSS signal results in a global average reduction in RMSE of 4.7 % with respect to the numerical non-tidal loading models. This approach presents an initial step towards a data-driven complement to physics-based numerical loading models, improving the isolation of non-tectonic signals in GNSS time series and validation of numerical non-tidal loading models. Graphical Abstract

Bo Yuan, Yuan Li, Jiachao Li et al.

CPVG (Utility-scale photovoltaic generation) is expanding rapidly worldwide, yet its cumulative ecological effects remain insufficiently quantified. This review synthesizes current evidence to clarify how CPVG influences ecosystems through linked mechanisms of energy redistribution, biogeochemical cycling disturbance, and ecological responses. CPVG alters surface radiation balance, modifies microclimate, and disrupts carbon–nitrogen–water fluxes, thereby driving vegetation shifts, soil degradation, and biodiversity decline. These impacts accumulate across temporal scales—from short-term construction disturbances to long-term operational feedbacks—and propagate spatially from local to regional and watershed levels. Ecological outcomes differ substantially among deserts, grasslands, and agroecosystems due to contrasting resilience and limiting factors. Based on these mechanisms, we propose a multi-scale cumulative impact assessment framework integrating indicator development, multi-source monitoring, coupled modelling, and ecological risk tiering. A full-chain mitigation pathway is further outlined, emphasizing optimized siting, disturbance reduction, adaptive management, and targeted restoration. This study provides a systematic foundation for evaluating and regulating CPVG’s cumulative ecological impacts, supporting more sustainable solar deployment.

D. Booge, D. Booge, J. F. Tjiputra et al.

<p>Oceanic bromoform (CHBr<span class="inline-formula">₃</span>) is an important precursor of atmospheric bromine. Although highly relevant for the future halogen burden and ozone layer in the stratosphere, global CHBr<span class="inline-formula">₃</span> production in the ocean and its emissions are still poorly constrained in observations and are mostly neglected in climate models. Here, we newly implement marine CHBr<span class="inline-formula">₃</span> in the second version of the state-of-the-art Norwegian Earth System Model (NorESM2) with fully coupled interactions of ocean, sea ice, and atmosphere. Our results are validated using oceanic and atmospheric observations from the HalOcAt (Halocarbons in the Ocean and Atmosphere) database. The simulated mean oceanic concentrations (6.61 <span class="inline-formula">±</span> 3.43 pmol L<span class="inline-formula">⁻¹)</span> are in good agreement with observations from open-ocean regions (5.02 <span class="inline-formula">±</span> 4.50 pmol L<span class="inline-formula">⁻¹)</span>, while the mean atmospheric mixing ratios (0.76 <span class="inline-formula">±</span> 0.39 ppt) are lower than observed but within the range of uncertainty (1.45 <span class="inline-formula">±</span> 1.11 ppt). The NorESM2 ocean emissions of CHBr<span class="inline-formula">₃</span> (214 Gg yr<span class="inline-formula">⁻¹)</span> are within the range of or higher than previously published estimates from bottom-up approaches but lower than estimates from top-down approaches. Annual mean fluxes are mostly positive (sea-to-air fluxes); driven by oceanic concentrations, sea surface temperature, and wind speed; and dependent on season and location. During winter, model results imply that some oceanic regions in high latitudes act as sinks of atmospheric CHBr<span class="inline-formula">₃</span> due to their elevated atmospheric mixing ratios. We further demonstrate that key drivers for oceanic and atmospheric CHBr<span class="inline-formula">₃</span> variability are spatially heterogeneous. In the tropical West Pacific, which is a hot spot for oceanic bromine delivery to the stratosphere, wind speed is the main driver for CHBr<span class="inline-formula">₃</span> fluxes on an annual basis. In the North Atlantic, as well as in the Southern Ocean region, atmospheric and oceanic CHBr<span class="inline-formula">₃</span> variabilities interact during most of the seasons except for the winter months, when sea surface temperature is the main driver. Our study provides an improved process-based understanding of the biogeochemical cycling of CHBr<span class="inline-formula">₃</span> and more reliable natural emission estimates, especially on seasonal and spatial scales, compared to previously published model estimates.</p>

ZHANG Yaguo 1, XIAO Shuxiong 1, YANG Yun 1, LI Tonglu 2

To study the contact problem between unsaturated soil and structure, based on the state-dependent concept and the critical state theory, by considering the influences of suction on the yield function, flow rule and hardening law and so on, an elastoplastic interface model is established with the net normal stress and the suction serving as stress state variables. The reliability of the model is demonstrated through the shearing tests on sand-steel and sand-geotextile interface. The results show that the proposed model can describe the mechanical behaviors of sand-structure interfaces under different initial states, and can predict the variations of shear stress, normal displacement and stress path of interface subjected to different boundary conditions (i.e., constant normal load, constant normal stiffness and constant volume condition) as well. Thereafter, the shearing test results of unsaturated silt-steel and completely decomposed granite (CDG)-cement interface under different suctions are predicted, finding that with the increase of suction, the shear strength of interfaces increases, the strain softening and dilatancy behaviors become more significant, and the shear displacement corresponding to phase transformation point representing the transition from contraction to dilation decreases. Compared to those of the existing models, the parameters of the proposed model are easier to be calibrated, the calculated results are closer to the measured data, and the decreasing trend of the shear displacement corresponding to the peak strength with suction can be reflected, indicating that the model here captures the effects of suction on the peak strength, critical state and hardening behaviors of the interface better.

Bin Wang, Liang Wu, Wenjia Li et al.

Abstract In early geological data analysis, most geological maps were drawn as raster images by hand or with software, and there were disadvantages such as the inability to edit at any time or change the scale with fidelity. Therefore, the use of modern information technology to perform in-depth processing of geological maps with outdated geological data can meet the purpose of repeated use, analysis, and further knowledge discovery. To address this issue, this study proposes a semi-automatic generation approach for generating geological profiles by integrating multi-source data. This approach utilizes the text content of the stratigraphic information layer in the geological report and the corresponding digital elevation model (DEM) data of the study area. It solves the problem of the reuse of outdated data and can reconstruct geological profiles at a low cost in the absence of field measurement data (e.g., drilling data). Finally, we propose two application scenarios, including lithology classification of the stratum and knowledge representation of each stratum object, both of which have sound application effects for further analysis and knowledge discovery. The semi-automatic reconstruction method proposed in this study considers the smooth treatment of geological profiles and topological relations between stratum objects. This method solves the problems of interleaving and morphologic coordination between stratum curves associated with previous methods. The result of the vector geological profile can be used for geographic information systems (GIS) functions such as spatial analysis and attribute queries.

Chao Zhang, Qingxiang Meng, Cheng Li

AbstractNear-surface imaging structures often plays a significant role in the field of environmental and engineering geophysics. Early-arrival waveform inversion (EWI) is state-of-the-art method to imaging near-surface structures due to its high resolution. However, the method faces with cycle-skipping issue which might lead to an unexpected local minimum. Envelope inversion (EI) could deal with this issue which contributes to the ultralow-frequency information extracted from the envelope but has a low resolution. We have developed a curvelet-based joint waveform and envelope inversion (CJWEI) method for inverting imaging near-surface velocity structures. By inverting two types of data, we are able to recover the low- and high-wavenumber structures and mitigate the cycle-skipping problem. Curvelet transform was used to decompose seismic data into different scales and provide a multiscale inversion strategy to further reduce non-uniqueness of waveform inversion efficiently. With synthetic test and real data application, we demonstrate that our method can constrain the anomalies and hidden layers in the shallow structure more efficiently as well as is robust in terms of noise. The proposed multiscale joint inversion offers a computational efficiency and high precision to imaging fine-scale shallow underground structures.

Tianshou Ma, Jin Huang, Zhilin Li et al.

A finite element model of wellbore stability was proposed for a horizontal well, and drill-string friction and lateral collision in the process of rotary motion were taken into account. An unconfined compression test was used for model validation, the normalized yielded zone area (NYZA) was employed to analyze wellbore stability, and the influence of a lateral collision on wellbore stability was simulated. The results indicated that the stress-strain curve of numerical simulation consists with unconfined compression test, and the maximum relative error is <2.2%. The evolution of NYZA can be divided into three typical stages: stage I (static balance), stage II (dynamic growth), and stage III (dynamic balance). Both normal and shear stresses reach to the peak value in stage II, while they always fluctuate in a relatively small range in stage III, so that the wellbore stability mainly affected by the first collision of drill-string. Both lateral acceleration and friction effects have significant impact on wellbore stability. The initial collision position and the size of drilling tool have a certain influence on wellbore stability, while the revolving speed of drill-string almost has no impact. The present paper has guiding significance for wellbore collapse prevention and drilling parameter optimization.

A. Rezaei, H. Hassani, P. Moarefvand et al.

ABSTRACT Lithological mapping using satellite images, particularly the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data help in effectively defining the best initial targets for regional exploration. ASTER data allow for the discrimination of rock units in the broader region. This research work is focused on the use of remote sensing techniques for geological mapping using ASTER satellite image and generating a geological map of Sangan region. The study area is located in southeast of Khorasan-e-Razavi province and at the eastern edge of the Khaf-Kashmar-Bardskan Volcano-Plutonic Metallogenic Belt in northeast Iran. Band ratio (BR), spectral angle mapper (SAM) and support vector machines (SVMs) methods were used for classifying the main lithologic units in Sangan region. The results of BR, SAM and SVM techniques were quantitatively compared with geological boundaries mapped in the field showing an accuracy of nearly 79 %. SVMs method, in comparison to conventional methods of classification, was known to provide superior results. As the final result of this research, integration of remote sensing and field investigations led to generating high accuracy geological map in the Sangan region. Application of the methods has invaluable implications for geological mapping and mineral exploration in inaccessible regions.

Yejia Qiang, Jian He, Te Xiao et al.

Study region: Hong Kong, China. Study focus: This paper aims to develop a flood analysis model to integrate the effects of multiple flooding triggers (i.e. rainfall, high sea levels and wave overtopping) during powerful tropical cyclones and investigate coastal flood hazards in an urban area at the street scale. The process of wave overtopping is properly estimated and integrated in a dual-drainage model in a maneuverable way as an inflow discharge hydrograph. The inundation during Typhoon Mangkhut, 2018, in Tseung Kwan O town center, a coastal community of Hong Kong, is taken as a case study. New hydrological insights for the region: The inundation scenario in Tseung Kwan O town center during Tyhpoon Mangkhut is reproduced and comparison between different drainage conditions demonstrates the key role of drainage facilities in the mitigation of flooding induced by wave overtopping, although the varying sea level boundary could partly reduce the drainage efficiency. In addition, possible flood scenarios and pedestrian stability in flowing water upon the unfavorable combination of storm surge and astronomical tide, as well as the effectiveness of a 1.1 m wave wall are evaluated. The overtopping discharge, flooding severity and dangerous zones for pedestrian can be markedly reduced by the wave wall.

A. Høyer, K. Klint, G. Fiandaca et al.

Abstract Groundwater protection and risk assessment of contaminated sites (e.g. abandoned landfills, industrial waste facilities, gasoline stations, and dry cleaners) situated in complex glacial landscapes are extremely challenging. A common method to assess the risks for leakage and contamination of groundwater and surface water is to develop hydraulic models. However, reliable models need to contain information about both the three-dimensional (3D) distribution of the deposits and their hydraulic properties. Environmental risk assessments therefore require highly detailed digital 3D geological models. In order to construct models with this degree of detail, dense data coverage with high-quality data is necessary. Many studies rely of few data sources, resulting in relatively sparse data. In this study we demonstrate how 6 different data sources can be combined to gain new insight on the geological history, which is central to the subsequent 3D geological modelling. The analyses in this study include (i) geomorphology, (ii) spear-auger mapping and near-surface electromagnetic induction data, (iii) borehole analyses, (iv) geoelectrical profiling, and (v) transient electromagnetic measurements. The study area is located on the island of Samso, in the central part of Denmark, where a digital 3D geological model is constructed. The model consists of combined layer and voxel models and covers a small area (~1 km2) surrounding a former landfill (Pillemark). The near-surface geology is characterized by a dead-ice landscape formed by glaciers during the Weichselian ice-age. By interpreting the new data it has been possible to update and revise the geological history, which was used during the development of a highly detailed 3D geological model. This model was constructed combining layers and voxels in order to better represent the complex geology and incorporate all the details provided by the different data sources. The novel geological understanding was used to update the risk assessment of the Pillemark landfill, where a remedial pumping today is on-going. The immediate risk is related to the migration of landfill leachate downgradient through a lacustrine sandy aquifer and wetlands. Groundwater used for drinking water purposes is abstracted from an underlying sand and gravel aquifer (Tebbestrup formation), which is protected by a clay till (mid Danish till) found in the entire Pillemark area. A vertical hydraulic gradient from the upper to the lower aquifer indicates groundwater flow. However, the actual impact of landfill on the deeper aquifer has to be assessed by a detailed evaluation of the drainage system, pumping schemes and groundwater quality in the area. The 3D geological model is an important step toward the development of a groundwater flow model, required in order to establish a water balance for the hydrogeological system and estimate the vertical transport.

E. Holden, Wei Liu, T. Horrocks et al.

Abstract Records of past exploration in open-file mineral exploration reports are an important source of information for mineral explorers. These reports document existing geological knowledge that may be relevant to modelling ore forming processes in a particular area of interest. This paper presents the development of GeoDocA, a geological document analysis system, that applies automated text analysis techniques with the specific aim of assisting geologists in browsing of and searching for documents based on relevant geological contents within a large repository of documents. GeoDocA analysed 25,419 exploration reports and using a customised set of keywords pertaining to broad categories such as mineral occurrences, rock types, alteration types, and geological time. An interactive user interface was developed to facilitate visual analysis of exploration reports. For individual reports, it provides a summary of their content in graph form, a gallery of extracted figures and tables, and a list of similar reports based on shared geological keywords. In addition, it assists document search efforts through auto-generated keyword suggestions which are based on associations of keywords learnt by the system from all reports in the repository. While the text mining methods reported here is the foundation for further development to incorporate semantic analysis towards geological knowledge extraction, the outcomes of this study demonstrate the effectiveness of automated text analysis in supporting a fast analysis of a large number of reports to identify the targeted mineral systems and their associated geological environments.

Zengxue Li, Dongdong Wang, Dawei Lv et al.

ABSTRACT China has abundant coal resources, which are extensively developed in marine-influenced, continental, and transitional environments. The coal-bearing strata in China have complicated geneses and distributions. There were eight major coal-forming periods in China, namely the Terreneuvian, Mississippian, Pennsylvanian–Cisuralian–Guadalupian, Lopingian, Late Triassic, Early–Middle Jurassic, and Early Cretaceous Epochs, as well as the Palaeogene–Neogene Periods. The distributions of the coal-bearing strata formed during these different coal-forming periods displayed obvious regional and regularity characteristics. In accordance with their plate-tectonic settings and coal-bearing characteristics, the coal-bearing basins in China can be divided into six types. The coal-bearing basins that were formed during the Palaeozoic Era were mainly large epicontinental sea basins. During the early Palaeozoic Era, the shallow sea was the most important coal-forming sedimentary environment. In addition, coastal delta and delta-detrital coast systems were the most important coal-forming sedimentary environments in the late Palaeozoic Era. The coal-bearing basins that were formed during the Late Triassic Epoch were mainly offshore basins, and coastal, coast-delta, coastal alluvial, and coastal inter-mountainous plain environments dominated their coal-forming sedimentary environments. Coast–bay and lagoon–estuary systems comprised additional main coal-forming sedimentary environments. The coal-bearing basins that formed during the Early–Middle Jurassic Epochs were large- and medium-sized inland lake basins, in which alluvial-lake delta systems recorded the best coal formation processes, followed by lakeshore sedimentary environments. The coal-bearing basins that formed during the Early Cretaceous Epoch and Palaeogene–Neogene Periods were mainly small-sized continental basin groups. Coal-forming processes mainly occurred in the lake-delta swamp environments during lake siltation stages when the filling evolution of the lake basins occurred. In addition, this study proposed a new coal-forming process that occurs during transgression events. Finally, this study generally summarized the characteristics and evolution theories of coal-forming processes in China and especially focused on the characteristics of the evolution of coal-forming sedimentary environments.

B. M. Urann, H. J. B. Dick, R. Parnell-Turner et al.

Plate tectonics necessitates mantle recycling throughout Earth’s history, yet direct geochemical evidence for mantle reprocessing remains elusive. Here, the authors present evidence of recycled supra-subduction zone mantle wedge peridotite dredged from the Mid-Atlantic Ridge near 16°30′N.

Sharon Aol, Stephan Buchert, Edward Jurua

Abstract Ionospheric irregularities can affect satellite communication and navigation by causing scintillations of radio signals. The scintillations are routinely measured using ground-based networks of receivers. This study presents observations of ionospheric irregularities by Langmuir probes on the Swarm satellites. They are compared with amplitude scintillation events recorded by the Global Positioning System-Scintillation Network and Decision Aid (GPS-SCINDA) receiver installed in Mbarara (Lat: $$0.6^{\circ }\hbox {S}$$ 0 . 6 ∘ S , Lon: $$30.8^{\circ }\hbox {E}$$ 30 . 8 ∘ E , Mag. lat: $$10.2^{\circ }\hbox {S}$$ 10 . 2 ∘ S ). The study covers the years from 2014 to 2018 when both data sets were available. It was found that the ground-based amplitude scintillations were enhanced when Swarm registered ionospheric irregularities for a large number of passes. The number of matching observations was greater for Swarm A and C which orbited at lower altitudes compared to Swarm B. However, some counterexamples, i.e., cases when in situ electron density fluctuations were not associated with any observed L-band amplitude scintillation and vice versa, were also found. Therefore, mismatches between observed irregularity structures and scintillations can occur just over a few minutes and within distances of a few tens of kilometers. The amplitude scintillation strength, characterized by the S4 index was estimated from the electron density data using the well-known phase screen model for weak scattering. The derived amplitude scintillation was on average lower for Swarm B than for A and C and less in accordance with the observed range. Irregularities at an altitude of about 450 km contribute strongly to scintillations in the L-band, while irregularities at about 510-km altitude contribute significantly less. We infer that in situ density fluctuations observed on passes over or near Mbarara may be used to indicate the risk that ionospheric radio wave scintillations occur at that site.

Qi Zhang, Hehua Zhu

Abstract A multi-source data standard must be established to reconcile all available geological data such as borehole data, geological mapping data, and rock property data for building a reliable 3D geological model. In addition, a methodology that considers various available data must be developed to provide accurate results that are easy to interpret and convenient for post-modeling analysis. This paper presents a collaborative analysis approach for geological body modeling using multi-source geological data and interpolation theories in different stages and at different places. This approach aims to provide a detailed and comprehensive description and analysis of data, with emphasis on processing flow. The proposed approach contains three major components: establishment of geological databases based on the multi-source data standard to incorporate borehole, geological mapping and rock property data; Combined Kriging interpolation method for data processing; geological algorithms to build, visualize, and post-analyze the 3D geological model. The model integrates multi-source information and is a representative of the geological context. The proposed method is validated by applying it to the Ma-luan mountain tunnel project in Guangdong province, China.

D. J. Brogan, P. A. Nelson, L. H. MacDonald

<p>Post-wildfire landscapes are highly susceptible to rapid geomorphic changes, and the resulting downstream effects, at both the hillslope and watershed scales due to increases in hillslope runoff and erosion. Numerous studies have documented these changes at the hillslope scale, but relatively few studies have documented larger-scale post-fire geomorphic changes over time. In this study we used five airborne laser scanning (ALS) datasets collected over 4 years to quantify erosion and deposition throughout the channel network in two <span class="inline-formula">∼15</span>&thinsp;km<span class="inline-formula">²</span> watersheds, Skin Gulch and Hill Gulch, in northern Colorado after a wildfire followed by a large, long-duration flood 15&thinsp;months later. The objectives were to (1) quantify the volumes, spatial patterns, and temporal changes over time of erosion and deposition over a nearly 4-year period, and (2) evaluate the extent to which these spatially and temporally explicit changes are correlated to precipitation metrics, burn severity, and morphologic variables. The volumetric changes were calculated from a differencing of DEMs for 50&thinsp;m long segments of the channel network and associated valley bottoms. The results showed net sediment accumulation after the wildfire in the valley bottoms of both watersheds, with greater accumulations in the wider and flatter valley bottoms in the first 2 years after burning. In contrast, the mesoscale flood caused large amounts of erosion, with higher erosion in those areas with more post-fire deposition. Only minor changes occurred over the 2 years following the mesoscale flood. Volume changes for the different time periods were weakly but significantly correlated to, in order of decreasing correlation, contributing area, channel width, percent burned at high and/or moderate severity, channel slope, confinement ratio, maximum 30&thinsp;min precipitation, and total precipitation. These results suggest that morphometric characteristics, when combined with burn severity and a specified storm, can indicate the relative likelihood and locations for post-fire erosion and deposition. This information can help assess downstream risks and prioritize areas for post-fire hillslope rehabilitation treatments.</p>

Shanjun Luo, Yingbin He, Zhuozhuo Wang et al.

Leaf area index (LAI) is one of the important variables for crop growth monitoring and yield estimating. In this article, the potato LAI was retrieved by several vegetation indices (VIs) and spectral parameters of the continuum removal method (SPCRM) to provide accurate estimates. A comparison of the two methods of retrieving precision was completed. The data source for computing VIs and SPCRM was hyperspectral reflectance data for the life cycle, derived from two potato cultivars, Favorite (early maturing variety) and Yanshu 4 (late maturing variety), through field experiments. Sensitive bands were identified to indicate seven VIs by correlation analysis. Additionally, seven SPCRM were computed. Based on these methods, the potato LAI was retrieved and tested. Meanwhile, a comparison of the retrieving precision was implemented. The results showed that compared with the filtered spectral reflectance and VIs, the correlation between the potato LAI and the continuum removal spectral reflectance and its retrieved SPCRM were higher. The determination coefficients (R2) of the retrieving models of four parameters, the total area (S), the left area (Sl), the right area (Sr) and the depth area ratio (W), derived from the continuum removal method were all above 0.801, and their fitting coefficients (r) were all above 0.868, with the mean relative errors (MRE) all <0.14. It was identified that W was the most suitable parameter for retrieving the potato LAI. Although the effectiveness of SPCRM requires further research, this study manifests that SPCRM have the potential to accurately retrieve the potato LAI.

M. Trifunac, A. G. Brady

S. Stern, R. Binzel, A. Earle et al.