Soil carbon pools play a significant role in regulating global carbon balance and mitigating greenhouse gases. Hence, estimating soil carbon stocks is critical for assessing the carbon cycle in terrestrial ecosystems. Based on the soil carbon data obtained from the land quality geochemical survey in the study area, this study estimated the stocks of total, organic, and inorganic carbon of various soil layers in Northwest China using the unit soil carbon amount (USCA) method. It analyzed the content characteristics of organic and inorganic carbon in soil under different soil, land use, and topographic types. The results of this study are as follows: (1) All the soil layers at depths ranging from 0 to 2 m in the study area exhibited total carbon of 10 099.4 Mt, including 1 224.8 Mt in the topsoil layer (0~0.2 m), 5 345.9 Mt in the upper soil layer (0~1.0 m), and 4 753.5 Mt in the lower soil layer (1.0~2.0 m). Inorganic carbon predominated in all the soil layers, with its proportion gradually increasing from top to bottom, whereas organic carbon was principally concentrated in the topsoil layer; (2) The high-value areas of inorganic carbon content were primarily distributed in the Huangshui Valley of Qinghai Province, and the Loess Plateau region covering the Longzhong area of Gansu Province, northern Shaanxi Province, and southern Ningxia Province. In contrast, the high-value areas of organic carbon content were chiefly distributed in the Qilian Mountains; (3) The aeolian sandy soil exhibited the lowest organic, inorganic, and total carbon contents in the topsoil and deep soil layers. The dark loessial soil and the loessal soil showed the highest inorganic carbon content in the topsoil layer. The dark felty soil and the dark loessial soil displayed the highest organic carbon contents in the topsoil and deep soil layers, respectively. Additionally, the dark felty soil had the highest total carbon content in the topsoil and deep soil layers; (4) Forests exhibited the highest organic carbon content in the topsoil and deep soil layers, and the highest total carbon content in the topsoil layer. Grasslands showed the highest inorganic and total carbon contents in the topsoil layer. Cultivated land had the highest inorganic carbon content in the deep soil layer. Bare land manifested the lowest inorganic, organic, and total carbon contents; (5) Mountains displayed the highest organic and total carbon contents in the topsoil and deep soil layers. Loess had the highest inorganic carbon content in the topsoil and deep soil layers. Plains showed intermediate carbon contents generally between those of loess and mountains. Besides, high-altitude areas manifested extremely high organic carbon content.

Over the past century, electromagnetic exploration technology has evolved from direct current resistivity and induced polarization methods to a comprehensive geophysical system. Yet, in China's new mineral exploration phase, challenges like deep-mining needs, cultural noise, and weak 3D interpretation limit traditional methods. High-power-ultrahigh-power electromagnetic technology, by boosting transmission current, combats these issues. It enhances detection depth, enables 3D exploration, and drives technological and application innovation. This paper reviews the development of high-power-ultrahigh-power electromagnetic instruments and current research. It emphasizes that technologies like true 3D full-waveform IP collection and inversion, tensor CSAMT collection and inversion, and multi-parameter joint inversion of time-and frequency-domain EM methods can strengthen deep-target detection. Future research should tackle anisotropic 3D inversion, full-domain inversion with a field source, and extracting polarization and magnetization rates under complex constraints. These advances will propel electromagnetic methods toward greater depth, precision, and intelligence, supporting China's renewed mineral exploration efforts.

Many cities or urban residential areas in central and western China reside in alluvial plains formed from piedmont alluvial fans. Hence, revealing the stratigraphic architectures and stability of alluvial fans holds critical significance for urban construction planning and rational land use. The alluvial fan in the eastern piedmont of the Liupan Mountains hosts the urban residential areas and villages of Guyuan City, with a dense population. Moreover, the alluvial fan develops several event deposits recording the activity of the alluvial fan under tectonic movements and climatic changes. Through field geological survey, optically stimulated luminescence dating, controlled source audio-frequency magnetotellurics (CSAMT), and conventional radon measurement, this study revealed the stratigraphic architecture of the alluvial fan and its two-phase event deposits (~43.33 ka B.P. and 22.92~20.72 ka B.P) since the Late Pleistocene. As indicated by the CSAMT and conventional radon measurement results, the alluvial fan still exhibits high activity under the influence of the Haiyuan and Qingshuihe faults. The results of this study provide fundamental data for crustal stability assessment, prevention and control of geologic hazards, and engineering construction in the Liupanshan area.

Recommendation system algorithms, having recently garnered significant attention in the field of digital Earth science, are expected to be widely applied in metallogenic prediction. Traditional metallogenic prediction studies fail to fully mine the various types of semantic information in massive geoscience data. The deep interest evolution network (DIEN), as a recommendation system algorithm, can fully mine semantic information to predict user preferences. Therefore, this study employed the DIEN model as the prediction model and the semantic information extracted from bedrock interpretation as the ore-controlling elements according to the database provided by the Western Australian government. The model was trained to perform metallogenic prediction for the study area. The prediction results indicate that 92.95% of uranium ore occurrences fell within the medium-high probability zone in the prediction map, with some unknown zones also showing high prediction probabilities. After removing known uranium ore occurrences in some zones, the retrained model still yielded medium-high prediction probabilities in these zones. The results suggest that the DIEN can effectively mine semantic information in metallogenic prediction studies, and the DIEN model exhibits strong predictive capacity for the study area, providing a novel approach for metallogenic prediction studies.

The Mangling ore concentration area with intense magmatic activity has become a focal area for deep prospecting in the North Qinling tectonic belt in recent years. The formation of molybdenum deposits in this area is closely related to small Late Jurassic acidic intrusions. To achieve breakthroughs in deep ore prospection within this area, this study conducted the wide-field electromagnetic sounding over the concealed Yaozhuang intrusion delineated based on gravity anomalies. The results indicate the presence of pronounced high-resistivity anomalies at depth, and it is inferred that the protruding part of the anomalies corresponds to the concealed Yaozhuang intrusion. The resistivity inversion results roughly delineated the variations in the top surface of the intrusion, with the elevations and N-S width of the top surface estimated at -300~620 m and 1300~1600 m, respectively. Drilling in the most favorable deep mineralized part confirmed the presence of the concealed intrusion and concealed molybdenum ore bodies. The results of this study demonstrate that the wide-field electromagnetic sounding method exhibits great sounding depths and high resolutions, serving as an effective method for deep ore prospecting in the Mangling ore concentration area.

In response to the increasing demand for large-scale field seismic acquisition, this study developed a low-cost multifunctional nodal rotational seismometer (RBWL) with a micro-electro-mechanical system (MEMS) sensor, considering the functionality, economic feasibility, and the ease of arrangement. The RBWL employs a low-cost and low-power MEMS sensor to acquire seismic signals, involving three-component translational motions (T_x,T_y,T_z) and three-component rotational motions (R_x,R_y,R_z). To reduce the impacts of environmental factors on measurements, the system of the RBWL automatically records real-time information including temperature and attitude while performing compensation correction on the measurement results. For real-time monitoring and data transmission at acquisition nodes, the system establishes a data transmission link integrating 4G, cloud, and client, with the measured maximum data transmission rate up to 100 Mbps. The testing of H/V spectral ratios verifies the system functions and principal performance parameters of the RBWL and its effectiveness in engineering physical exploration.

The Mianning-Dechang area in western Sichuan serves as the most important metallogenic belt of light rare earth elements (LREEs) in China. To make breakthroughs in the exploration of rare earth resources in the Dechang area, a 1:50 000 stream sediment survey was conducted in this study. The analysis of test data characteristics and the extraction of geochemical anomalies reveal that the total rare-earth oxides (REOs) in the area exhibit a pronounced enrichment pattern and that element anomalies largely overlap the spatial distribution of related geological bodies. Through comprehensive analysis using the cumulative frequency method and iterative method, this study determined the lower limits of anomalies and, accordingly, plotted element anomaly maps, with five main anomaly areas being delineated. The comprehensive evaluation of anomalies revealed four prospecting target areas: Huangjiaba, Jiaobacun, Yibasan, and Huajiaoyuan. The analysis of metallogenic geological conditions and the anomaly verification based on drilling in the Gannan area led to the discovery of three light rare earth deposits in the Huangjiaba prospecting target area, two heavy rare earth deposits in the Jiaobacun prospecting target area, two heavy rare earth deposits in the Yibasan prospecting target area, and two heavy rare earth deposits in the Huajiaoyuan prospecting target area. This study posits that the Triassic biotite moyite and biotite monzogranite in the study area are the metallogenic parent rocks of ion adsorption-type rare earth resources, with REEs primarily undergoing enrichment and mineralization in completely weathered layers. Therefore, a simple and effective prospecting pattern for "endogenous and exogenous" ion adsorption-type rare earth deposits in the Dechang area consists of analyzing the geochemical characteristics of the total REOs based on a 1:50 000 stream sediment survey, delineating metallogenic prospect areas that indicate parent rocks for REE enrichment, and selecting sections favorable for the formation and preservation of weathered crusts based on the hypergenic conditions of the enrichment areas, thus achieving the quick delineation of the prospecting target areas.

Underground research laboratories (URLs) for the geological disposal of high-level radioactive waste serve as critical facilities for verifying the safety and suitability of the sites of potential disposal repositories and for developing disposal technologies. URLs are irreplaceable in many aspects such as the siting and system design of potential disposal repositories, the development of the theories and technologies for disposal engineering, the safety and characteristic assessments, full-scale field tests, and on-site demonstration. This study highlights the definition, classification, and functions of URLs and categorizes existing primary URLs both in China and abroad. URLs are generally categorized into general URLs (first generation) and site-specific URLs (second generation). The construction of disposal repositories in China has progressed from national, regional, and site screening to site evaluation and to URL construction. The authors of this study proposed the concepts of "site-specific URLs" and "third-generation URLs" in 2010 and 2014, respectively. Furthermore, the Beishan URL-the world's first site-specific URL for the geological disposal of high-level radioactive waste-has been built. This study introduces the siting process, planning, positioning, and functions of the Beishan URL, as well as the functions of primary scientific experiments and main field experiments conducted during its construction. The results of this study serve as a guide for future siting and R&D of disposal repositories.

With the application of high-precision,high-density 3D seismic technology and significant improvements in acquisition efficiency,the volume of data from nodal seismic data acquisition has expanded sharply.This leads to growing demands for the quality monitoring of nodal seismic acquisition.Especially,the lag in the synthesis of common shot gather data in node data has affected the quality monitoring and processing efficiency of seismic data.Therefore,the demand for quality control technology has become increasingly prominent in nodal seismic data acquisition.By delving into technologies including the visual monitoring of pre-acquisition node states,node data synthesis,and seismic data quality monitoring,this study independently developed a quality monitoring platform for nodal seismic data acquisition,enabling quality control for the whole nodal seismic data acquisition,involving equipment status,data synthesis,and data quality control.This platform has achieved satisfactory application results in a practical seismic data acquisition project.

The Salt Lake geothermal field in Yuncheng City, Shanxi Province, China lies beneath a densely populated urban area, posing significant challenges to further geothermal exploration and extraction. Based on the distribution of geothermal gradients in the geothermal field, which are higher in the southwest and lower in the northeast, a NE-trending microtremor survey profile was arranged in the southern part of Yuncheng City, aimed at investigating the deep geothermal reservoir structure and NW-trending structures in the geothermal field. The 2D velocity structure profile reveals a pronounced low-velocity anomaly in the eastern part, which is supposed to be induced by the fault fracture zone formed by multiple NW-striking tensional faults. Spatially, this concealed fault zone roughly corresponds to the low-geothermal gradient anomaly in the northeastern Salt Lake geothermal field, suggesting that this fault fracture zone might facilitate the rapid infiltration of cold surface water, thereby lowering the temperature of deep rocks in the northeastern part, leading to the formation of a large-scale low-temperature anomaly zone. Additionally, the faults identified by the microtremor survey can be traceable and confirmed in a controlled source reflection seismic profile in the study area, demonstrating the complementary nature of the two methods. This study further reveals the deep geothermal structures of the Salt Lake geothermal field based on previous efforts. This study provides more valuable bases and guidance for future exploration and resource evaluation of geothermal fields in the region while also demonstrating the effectiveness and superiority of the microtremor survey method in research on urban geothermal resources.

To evaluate the resource potential of the Jinchanshan mining area, this study conducted analysis and tests of metal element content in soil samples from two geochemical profiles using the electro-adsorption method. By combining the geological conditions of the mining area, this study revealed pronounced positive geochemical anomalies of Au, Ag, Cu, Pb, and Zn above the known gold deposits. The anomalous areas corresponded well with deposits, confirming the effectiveness and feasibility of the electro-adsorption method in the study area. The study identified geochemical anomalies Ⅰ and Ⅱ to the west of the Guaibanggou-Yangpo-Xiaoxigou mineralization zone in the first geochemical profile. Along the second profile, located between the Guaibanggou-Yangpo-Xiaoxigou and Nandawa-Limazigou-Loufengmao mineralization zones, anomalies Ⅲ and Ⅳ were observed at the westernmost end. The comprehensive geological analysis of the mining area indicates that the Ⅰ and Ⅲ anomaly zones exhibit favorable geological conditions for mineralization, serving as play fairways. The play fairway prediction conducted in this study provides targets for future exploration in the mining area.

The telecontrol electrode array is a new type of electrode array for power supply and observations that utilizes the carrier waves of the power-supply and measurement wires used in conventional electrical prospecting to transmit signals. By remotely controlling a series of coded electrode switches between various wires and their connections, this array allows for orderly power supply and measurements. This array enables flexible spacings between electrodes and the gradual expansion of the distances between power supply electrodes via remote control, thus achieving a gradient-based sounding array. The borrowing-line remote controller can be used combined with single-channel, multi-channel, and high-density resistivity instruments, and the combined arrays can perform 2D/3D electrical prospecting more effectively. Followed by the brief introduction of the principle of the borrowed-line telecontrol electrode array, this study discusses the applications and examples of this array and several combined arrays in the resistivity method and induced polarization (IP).

The deep mining of geological mineral information from geochemical exploration data has been a hot research topic in mathematical geology and geological big data. Despite China's abundant regional geochemical exploration data, the deep mining of geological mineral information from these data remains limited, necessitating a scientific, efficient, simple, and feasible data processing workflow and analytical methodology. This study investigated the Gaoqiao area in Huixian County, Gansu Province, China. According to the geological background and the theories of element properties and geochemical behavior, this study processed relevant element data to mine the geological mineral information in geochemical exploration data. It established preliminary mathematical models for the boundary delineation and lithofacies classification of intermediate-acid rock masses, and the boundary delineation of mafic volcanic rocks in the Gaoqiao area to scientifically guide geological mapping. It preliminarily established the target delineation model for tectonic altered rock-hosted gold deposits. The model's effectiveness was substantiated by seven newly delineated target areas with promising prospecting potential. The mineral inspection identified five ore occurrences, including four reported for anomalies related to mineralization, with two currently under provincial geological exploration. The results of this study show that by calculating and processing data based on the geochemical properties of elements, the hidden information in regional geochemical exploration data can be further mined to effectively guide and modify geological mapping, thereby enhancing mapping efficiency and quality. High-quality anomaly information can be further extracted from geochemical exploration data to effectively guide mineral prospecting in new areas.

Due to dense buildings and structures and insufficient drilling surveys, the construction of shield tunnels passing through urban karst formations that host dense buildings faces significant risks of surface fracturing and subsidence caused by karst development. Hence, this study employed the microtremor survey technology with strong anti-interference capability in complex environments to address this challenge. Based on the technology, it analyzed the structural characteristics of wave velocities in underground rock formations through the inversion of the apparent shear-wave velocity profile. Combined with geological drilling data, it inferred the bedrock interface, highly weathered unconsolidated formations, and karst cave anomaly zones. Key findings are as follows: (1) The apparent shear-wave velocities in the study area gradually increased from the shallow to deep formations. Formations with wave velocities above and below 300 m/s were inferred to be limestone and Quaternary formations, respectively, with the rock-soil interface at depths approximately between 10~15 m; (2) Seven low-value anomaly zones of apparent shear-wave velocities ranging from 150~240 m/s were interpreted. They were presumed to be unconsolidated formations or karst caves at depths ranging from 8~30 m. Relying on strong anti-interference and high accuracy, the microtremor survey technology can accurately identify the shear-wave velocity structures of underground profiles, lithologic interfaces of formations, unconsolidated formations, and karst cave anomalies. Therefore, the technology is effective in the geological exploration of urban dense building areas with karst development.

In practical detection operations using ground-penetrating radar (GPR), factors such as environmental noise and instrument errors frequently cause signals to be mixed with substantial noise, seriously reducing signal quality and the reliability of analytical results. To address this issue, this study proposed a time-frequency peak filtering method combined with minimum mean cross-entropy (TFPF-MMCE) for denoising GPR signals. This method combined time-frequency peak filtering with the cross-entropy function, enabling effective noise suppression and precise preservation of valid signals through precise optimization of the time-frequency representation, thereby significantly improving the quality of GPR signals. Numerical simulation and field GPR experiments validated that the TFPF-MMCE method exhibited a high noise removal capability and, thus, can effectively eliminate random noise while significantly improving signal clarity and reliability. Compared to traditional denoising methods, TFPF-MMCE shows significant advantages in denoising effectiveness and noise resistance stability, suggesting promising application potential and practical value in the field of GPR signal processing.

In the past two decades, high-sensitivity ring laser gyroscopes have demonstrated the potential of rotational observation data in global seismology. Commercial fiber-optic three-component rotational seismometers have heralded a new development phase of rotational seismography. Field experiments for high-sensitivity portable fiber-optic rotational seismometers in China remain in the initial stage, whereas their relevant data analysis results have been obtained internationally. This study elucidated the co-located observation experiments on six components (6C, including three components of translational motions and three components of rotational motions) of an active source and a natural earthquake, involving experimental schemes, implementation steps, and subsequent data analysis. Moreover, this study revealed the primary factors influencing the experiment results by comparatively analyzing the similarities and differences of experiments. Fiber-optic rotational and conventional seismometers need to be fixed on the same rigid panel to ensure the consistency of received signals. Besides, proper ground coupling and burial processing contribute to high-quality experimental data. The experimental results indicate that water bodies will affect surface wave manifestation and P-wave clarity. These findings, enriching the practical experience in seismic rotational observation experiments, serve as a reference for the design of subsequent rotational observation experiments, thereby assisting in completing the experiments and obtaining higher-quality data. In terms of data application, this study optimized and substantiated the feasibility of the preprocessing scheme, with the backazimuth calculation accuracy improved by 58.8° and 50° at the two active-source measuring points, and by 24.1° and 29.4° at the two passive-source measuring points. The application of six-component seismic data from a single seismic station suggests that additional observation of rotational components can acquire more seismic wavefield information, thus the observation of rotational components can be employed to enhance the utilization of China's massive seismic observation data. Overall, fiber-optic rotational seismometers broaden the boundary of seismic monitoring technology, boost seismology research, and create new possibilities for future earthquake research.

Non-destructive testing of the internal structural characteristics of ancient buildings is the key to preserving cultural relics.To determine the structures and internal defects of the ancient Great Wall in Linhai City,this study performed non-destructive testing of the wall structures in different orientations using a ground-penetrating radar (GPR) combining 100 MHz and 270 MHz antennas.The testing results show significant structural stratification in the ancient Great Wall.The GPR signal-reflected images reveal clear internal wall defects like pores,cracks,voids,and other hidden dangers.This study demonstrates the reliability of the GPR in detecting structures and defects of ancient walls,there by providing technical support for the structural protection of the ancient Great Wall.

The Triassic strata in the Lunnan area of the Tarim Basin represent a continental deltaic sedimentary system,with sedimentary subfacies including deltaic plain,deltaic front,and prodelta.The rapid phase transition of reservoirs and the high-frequency sand-mudstone alternating deposition create thin,highly heterogeneous reservoirs,rendering high-precision reservoir prediction extremely challenging.Under the guidance of sedimentary petrology and seismic sequence stratigraphy,this study conducted comprehensive seismic and geological research.Then,based on isochronous sequence interpretation,as well as seismic facies analytical results,this study established a lithofacies model.By constraining the pre-stack geostatistical inversion process,this study determined the spatial distribution of sand bodies.The practical application demonstrates that the proposed method enhances the vertical resolution of heterogeneous,thin reservoirs while significantly reducing lateral uncertainty.The predicted results align with actual drilling and production performance data and thus can provide valuable support for the efficient exploitation of hydrocarbon reservoirs.

The geomagnetic field is a vector field in space. However, traditional marine magnetic surveys focus on geomagnetic field intensity, failing to fully acquire and utilize rich information about the geomagnetic vector field. Given this, this study developed a towed marine geomagnetic vector measurement system. This system was designed to operate in dynamic marine conditions and ultimately acquire geomagnetic vector field data within the geographical coordinate system. Through sea trials of the system, grid line and repeat line measurements were obtained. After preprocessing the collected data, the measurement accuracy of repeat lines and crosspoints was better than 6.7 nT and 6 nT, respectively. The results of the sea test indicate that the measurement system has the preliminary ability to measure the geomagnetic vector field at sea, and it can be applied to geomagnetic field measurement tasks near or far sea, obtaining richer geomagnetic field information.

Seismic data processing reveals that internal multiples exhibit highly complex formation mechanisms,making their accurate identification and effective suppression a persistent challenge in geophysical exploration.Traditional methods for internal multiple suppression frequently require manual identification of subsurface reflection interfaces,making them difficult to apply to complex underground medium structures.Moreover,these methods are not only computationally cumbersome but also typically ensure only temporal and positional consistency when predicting internal multiples.The amplitude often deviates from observed values,requiring adaptive matching subtraction algorithms for effective suppression.This study developed an internal multiple suppression method based on Marchenko theory.Specifically,the wavefield relationships between the focusing function and Green’s function were constructed using the convolution and correlation reciprocity theorem of the Green’s function during data processing.The Green’s function was then solved using the focusing function,yielding either multiples or primaries constructed from the Green’s function.This method requires only the background velocity or the original data as operators during the iterative multidimensional correlation and convolution process,rendering it simple and computationally efficient. This study constructed an expression for the primary wave field using the Green’s function and the Marchenko equation.The tests using the SMAART model and actual data from the Gulf of Mexico demonstrate that the Marchenko method can effectively suppress internal multiples under the conditions of complex subsurface media.The iterative process requires no velocity information,providing significant advantages over conventional methods and great potential for application in complex underground environments where layers are difficult to distinguish.

This study investigated data from a 1:50,000 stream sediment survey in the Juxian-Wulian area, Shandong Province using factor analysis. By extracting eight representative factors, this study identified element assemblage types. Then, this study performed geochemical zoning based on the factor scores and discussed the relationships between various sub-zones and their geological background. Based on the geochemical zoning results, as well as geological conditions for mineralization, this study determined favorable geological bodies and prospecting targets and discovered new prospecting clues.The most significant mineralization combination in this area is Au-Cu-Ag-Mo-Bi, followed by Pb-Zn; The V-Ti-Co-Mn combination and Ni-Cr combination can serve as exploration elements, indicating that there may be favorable mineralization mechanisms in the center and deep parts of the combination anomaly zone. Finding volcanic craters and hidden explosive breccia tubes in the distribution areas of volcanic rocks in this region or area is an important direction for mineral exploration; In the area of Shichang Fangzi Village in the eastern part of the research area, there is a comprehensive zoning with a F₂-F₄-F₁ three factor combination model. The Mesozoic Buliu sequence and Weideshan sequence rock bodies are favorable geological bodies for mineralization, and the NE trending structural belt is a favorable place for mineralization, indicating the direction of prospecting.

In shallow engineering investigations, the small-loop transient electromagnetic (TEM) system is challenged by limitations such as overweight equipment, significant transmitter-receiver mutual inductance, and high manpower requirements. Hence, this study introduced an improved system. Based on the opposing-coils transient electromagnetic (OCTEM) theory, this study calculated the magnetic field distribution of the generalized opposing-coils antenna device. Furthermore, it designed and developed efficient portable antennas and the supporting system (collectively referred to as the portable OCTEM system). Subsequent field experiments demonstrate that while ensuring exploration accuracy, the portable OCTEM system can enhance the investigation efficiency by effectively mitigating the transmitter-receiver mutual inductance and significantly reducing manpower requirements. This study preliminarily verifies the feasibility of the portable OCTEM system, providing a novel technology route for developing downsized shallow exploration equipment.

Marine controlled-source electromagnetics (MCSEM) is used to explore resources such as oil and gas hydrates, as well as deep geological structures, by revealing resistivity differences below the seabed. Different excitation frequencies correspond to varying detection depths. To enhance the resistivity imaging of targets beneath the seabed, this study investigated the MCSEM-based technology for generating arbitrary-frequency waveforms to flexibly alter the excitation frequency and improve the exploration effectiveness and efficiency. Using the direct digital frequency synthesis (DDS) chip AD9833 and the joint control of a microcontroller and a complex programmable logic device (CPLD), this study achieved the generation of arbitrary-frequency waveforms with limited precision. The test results indicate that this technology can effectively enhance the spectral adaptability and flexibility of MCSEM.

The method of structural superimposed halo to find blind ore is a new method to find blind ore, which is based on the study of the theory of primary halo to find blind ore-the axial zoning of primary halo, and puts forward two new theories of ‘primary superimposed halo theory’ and ‘structural superimposed halo theory’. The accuracy of blind ore prediction by superimposed halo of structure is determined by the correctness of prediction marks and indexes. Based on the summary of seven common signs of structural superimposed halos in the prediction of deep blind ore deposits in more than 100 hydrothermal deposits, four important quantitative qualitative prediction signs are upgraded to quantitative prediction indicators. The structural superimposed halo prediction signs and indicators of 17 different combinations of accurate prediction of blind ore and discrimination of ore body denudation degree in the deep and periphery of the mining area are described in detail, and a practical ideal model of structural superimposed halo for predicting blind ore and discriminating ore body denudation degree is established. The common prediction signs and indicators of the model have important guiding significance for the prediction of deep blind ore in typical hydrothermal deposits, and have achieved remarkable prospecting results in more than 100 mine applications.

The exploration and exploitation practices in the Sichuan Basin in recent years indicate that breakthroughs have been achieved in the Jurassic continental tight sandstones.Nevertheless,due to the low porosity and permeability of tight sandstone,conventional post-stack inversion frequently exhibits limited resolution,failing to meet the accuracy requirements for the prediction of actual exploration reservoirs.This necessitates pre-stack inversion for detailed characterization of tight sandstones,while S-wave velocity is crucial to pre-stack inversion.Based on continental exploration wells drilled in the southeastern Sichuan Basin in recent years,this study developed a petrophysical modeling technique for dense sandstones in this region.Specifically,given the low permeability of tight sandstones and the uneven mixing of fluids in the pore space,the Domenico model was preferentially employed to calculate the pore fluid modulus.Although fluid modulus and density are inevitably variable under the actual subsurface conditions,previous studies typically use constant values to conduct petrophysical modeling for tight sandstones.In this study,depth-dependent values were applied.Tight sandstones in the southeastern Sichuan Basin generally exhibit a porosity of less than 10%.Therefore,calculations using the Nur and the Krief models will yield high errors.Given this,this study preferred using the Lee-Pride model to calculate the skeleton modulus and controlled the relationship between the rock matrix and the skeleton by introducing the value of the cementation parameter.The application of the established petrophysical model of tight sandstone to an actual survey area indicates high agreement with data from actual wells.Additionally,based on log statistics,Poisson's ratio,the most sensitive parameter is used for high-precision pre-stack inversion in the proposed technique,enabling detailed characterization and prediction of the internal structure of channel sandstones.

The Autonomous Underwater Vehicle (AUV) equipped with a magnetometer conducts underwater magnetic anomaly detection, enabling long-duration and large-scale continuous sampling. It offers advantages such as concealment, high efficiency, high practicality, wide application range, strong maneuverability, and robust endurance. To improve measurement accuracy, synchronous seabed magnetic field data is needed as a reference to counteract environmental magnetic noise. To address this, a submarine optically pumped magnetometer was developed to provide a reference for processing AUV magnetic anomaly detection data.The submarine optically pumped magnetometer consists of a magnetic field measurement unit and an acoustic release unit, capable of high-precision autonomous acquisition of the total magnetic field on the seabed, as well as underwater acoustic release and recovery. The magnetic field measurement unit includes an optical pumping probe, electronic unit, counter, battery pack, and nylon pressure chamber. The acoustic release unit includes an acoustic transducer, acoustic communication board, electro-corrosion decoupler, cement block, buoyancy block, and frame. This design addresses key technical challenges such as miniaturization, autonomous acquisition, and underwater acoustic communication.In 2022, a magnetic anomaly detection test was conducted in the offshore waters of Qingdao. The test results verified the autonomous seabed magnetic field acquisition and the release and recovery functions of the submarine optically pumped magnetometer, providing effective reference data for underwater target detection.

The Galinge iron deposit in Qinghai is overlain by deposits measuring greater than 150 m in thickness. The great burial depths of ore bodies lead to gentle magnetic anomaly morphology, making it difficult to characterize the spatial distribution of ore bodies. Therefore, this study employed three-dimensional magnetic anomaly inversion to determine the three-dimensional distribution characteristics of subsurface magnetic intensity in the study area. Given the prior information of non-magnetic surrounding rocks, the three-dimensional magnetic intensity model clearly presented the spatial distribution of the ore bodies and reflected the presence of intense magnetic bodies at depths of less than 500 m in existing boreholes. Accordingly, it can be inferred that there exist concealed ore bodies at depths exceeding 500 m in the study area. The results of this study suggest that three-dimensional magnetic anomaly inversion can effectively improve target identification, providing clear information on the horizontal positions, depths, and scales of magnetic ore bodies. The proposed inversion method can offer strong support for drilling design and reserve estimation, warranting promotion in detailed exploration of solid minerals.

In thereconstruction of actual subsurface structures, strong noise limits the accuracy of the magnetotelluric (MT) method,causing adverse effects on later data interpretation. Given this and the characteristics of the MT time series,this study analyzed different types of noise in the MT time series,proposing a signal denoising technique based on variational mode decomposition (VMD) and long short-term memory (LSTM) predictive reconstruction. First, baseline drift correctionwas performed for the original MT datausing the VMD signal decomposition algorithm. Then, the time series was further decomposed into multiple different intrinsic mode functions (IMFs) through VMD. The LSTM time series detection model was trained using interference-free data in the RSE component, which was then identified. Afterward, the time intervals containing noise weremarked, the increasement of noise was calculated, and the noise information wastransmitted to the original signal for truncation and removal. Finally, an LSTM multi-dimensional prediction model was trained for the IMFs, followed by the prediction of missing values under various modes. The predicted results under all modes were combined to obtain the final predicted MT signals. After signal reconstruction, a secondary signal-noise separationwas performed for spike-pulse noise that was not effectively identified through VMD. TheVMD-LSTM-based signal denoisingtechnique can accurately identify strong noise in MT signals by merely processing the time series intervals containing noise, thuseffectively preserving interference-free data. Moreover, its prediction errors can berestricted within the allowable error range of the data processing for MT signals. Therefore, this technique enjoys significant denoising effects.

The construction of the Beishan underground research laboratory (URL) is a key initiative under China's 13th Five-Year Plan. During the construction and operation of the URL, extensive scientific data will be generated in field experiments. To ensure the integrity, reliability, authenticity, and traceability of these data and to ensure that researchers can manage and utilize various types of data in an efficient and convenient manner, it is necessary to develop a dynamic management system tailored for the scientific data of the URL. The purpose is to provide data support and a decision-making basis for the R&D of disposal engineering technologies and safety assessments. This study introduces the background and overall requirements for the development of the scientific data dynamic management system for the Beishan URL, proposes a general design scheme, and provides a comprehensive overview of the system's functional architecture and content. The system is primarily composed of modules for system management, system status management, basic data management, metadata management, experimental information management, experimental data management, data quality management, and data visualization. This system has been preliminarily applied to the management of field experimental processes and data for the Beishan URL, yielding encouraging results.

This study investigated the Panxi area as an example to delineate faults and determine their current activity levels using aeromagnetic data and precise relocation results of small earthquakes. A total of 42 faults were delineated in the study area. Among them, 21 faults were inferred to be active currently, including 10 newly inferred active faults. This study examined the three-dimensional structural characteristics of some local sections of major faults in the study area. The results indicate that precise relocation results of small earthquakes can identify highly active faults and characterize their deep structures. Additionally, based on the delineation of basement faults using aeromagnetic data, the locations of active faults were constrained, and concealed active faults within the sedimentary cover were also determined. The proposed method holds certain practical significance for promoting research on the spatial distribution and activity of fault structures using aeromagnetic data.

As a semi-airbone transient electromagnetic (TEM) platform, drones inherently generate electromagnetic signals that may interfere with the collected transient electromagnetic data. This study investigated the impacts of drone noise on the collected data. Through outdoor experiments and systematic performance testing, this study analyzed the impacts of drone noise under varying rotor speeds, suspension lengths, flight height, and flight speeds. Accordingly, this study proposed methods for suppressing drone noise, such as determining the optimal suspension length and incorporating shielding layers. The study was conducted using the KWT-X8L-25 octocopter drones, but the research methodology and philosophy are also applicable to other drone models, thus serving as a reference for the selection of semi-airborne TEM platforms.

This study aims to improve the seismic exploration effects in the Upper Paleozoic strata of the Yin'e Basin.With the Juyanhai depression in the western Yin'e Basin as an experimental area,it investigated the previous seismic acquisition characteristics and current data processing techniques of the area.Through field seismic acquisition experiments and data processing research in the laboratory,it explored and summarized the seismic exploration techniques for the Upper Paleozoic strata in the Yin'e Basin.Key findings are as follows:(1)The combination of shot holes and seismic vibrators is recommended for seismic excitation in the area according to local conditions;(2)The receiving array length takes precedence over the receiving density;(3)Targeted processing techniques including anisotropy processing,spectral-constrained deconvolution,and wedge transform adaptive denoising can effectively improve the quality of deep seismic imaging.This study provides a reference for relevant research in similar areas.

Currently,velocity spectrum analysis methods widely used for ground-penetrating radar(GPR) signals mostly construct velocity spectra by superposing the amplitude energy of coherent signals to estimate electromagnetic wave velocities in subsurface media.In the case of multiple peaks and troughs in signal wavelets,velocity spectra constructed using these amplitude-based methods display multiple energy clusters,adversely affecting the identification,picking,and velocity estimation of subsequent energy peaks.Hence,this study proposed a method for estimating electromagnetic wave velocities in subsurface media based on common-offset GPR signal envelope and 3D velocity spectrum analysis.By scanning the signal envelope of hyperbolic diffracted waves in the GPR profile,the proposed method constructed the 3D velocity spectra of superimposed energy varying with zero-offset two-way travel time,test velocity,and measuring point position.Moreover,it extracted the slices of 2D velocity spectra according to the positions of hyperbolic vertices in the 3D velocity spectra.On this basis,the test velocities corresponding to the energy peaks in the slices of 2D velocity spectra were picked as the electromagnetic wave velocities in subsurface media.The numerical test results show that compared to the amplitude-based methods,the signal envelope-based 3D velocity spectrum analysis method obtained velocity spectra characterized by fewer continuous energy clusters,more concentrated energy,and minor velocity estimation errors,thus more effectively constructing the velocity model with inverse-time migration.

To determine the optimal prospecting target in the Bishan area, Xianghuang Banner, Inner Mongolia, this study conducted a geochemical survey at 1∶10,000 scale. Using multivariable statistical analysis, this study analyzed 14 elements (i.e., Au, Ag, Cu, Pb, Zn, Mn, Mo, Li, W, Sb, Bi, B, Hg, and As) in soil samples from the study area. The results indicate that six elements, including Au, Ag, Pb, Zn, Li, and As, exhibited high enrichment degrees, suggesting their significant metallogenic potential. The anomalies of high-content elements are principally dictated by the outer contact zone between tuffs/tuffaceous volcanic breccias and granites in the Lower Permian Sanmianjing Formation. The ore-forming elements are primarily controlled by the NW-trending fault zone. Alterations like silicification, binarite, pyrite, galena, and sphalerite alterations serve as principal prospecting markers. Based on the geological conditions for mineralization in the Bishan area, this study delineated three composite anomalies and two prospecting targets, with Ag ore bodies discovered through engineering validation. Soil geochemistry proves crucial for the successful identification of polymetallic ore bodies, thereby providing a significant foundation for subsequent mineral exploration efforts.

Conventional splicing methods aim to serve structural interpretation and align the reflection energy and frequency of large strata based on seismic data themselves.They adopt seismic data only from one study area in processing data of overlap zones,failing to fully utilize the effective information in seismic data of all study areas.Consequently,the resulting low-fidelity seismic data in overlap zones severely affect subsequent discrimination of reservoir connectivity and hydrocarbon-bearing properties.This study proposed a weighted fusion-based data spicing method for overlap zones,where seismic data from different study areas are fused with corresponding weights to generate a trace of seismic data.The application of the proposed method to actual seismic data shows that the processing results based on the fusion and splicing of data in overlap zones can effectively improve the quality of seismic data,with high continuity of seismic events on the profile, contributing significantly to the discrimination of the connectivity of shallow sand bodies.

Understanding the distribution patterns of selenium in soils and crops is critical to developing selenium-rich industries. Enshi City in Hubei Province is known for its extensive selenium-rich soils, establishing this city as a promising area for selenium-rich agriculture. This study investigated Xintang Township in Enshi. Based on the organization and analysis of the geochemical data of 2 469 soil samples and 237 crop samples of maize, potatoes, rice, radish, cabbage, and tea, this study offered a systematic summary of the selenium distribution in soils and factors influencing selenium content in crops in the study area. The results indicate that the topsoils exhibit selenium content ranging from 0.14×10^-6 to 25.74×10^-6, with a background value of 0.81×10^-6, which is 3.7 times the national background of selenium content in soils. Selenium-rich soils cover 86.23% of the total area of the study area, and two NEE-directed selenium-rich belts are found. The spatial distribution of selenium in soils is closely related to soil-forming parent materials. Soils with Permian black rock series as parent materials exhibit notably higher selenium content, with an enrichment coefficient of 3.74. In high-selenium-content areas, rice, radish, and cabbage exhibit selenium enrichment rates exceeding 65%. Except for potatoes, crops display positive correlations between their selenium content and the selenium content in their root soils, with tea showing the highest correlation (P<0.01, R=0.84). This suggests a close relationship between the selenium content in crops and their root soils. The crops in cultivated areas with Permian black rock series and Triassic carbonate rock series as soil-forming parent materials exhibit high bioconcentration factors of selenium, with soils and crops with Permian black rock series as soil-forming parent materials presenting the highest average selenium content. This highlights the significant impacts of soil-forming parent materials on crop selenium content.

Seismic data collected in the field frequently suffer from missing values due to constraints of acquisition cost or terrain. Data reconstruction is a critical step in seismic data preprocessing. Based on the compressed sensing theoretical framework, this study subsampled synthesized data using the 2D random undersampling technique. Then, the 3D seismic data were divided into a series of time slices. By introducing the sparse Shearlet transform and using the convex set projection (POCS) algorithm, this study conducted sequential data reconstruction for various time slices. As a result, a Shearlet transform-based time-domain 3D seismic data reconstruction method was developed. Numerical experiments and measured results demonstrate that the proposed reconstruction method exhibits a higher signal-to-noise ratio, a higher computational speed, and better effects than a Curvelet transform-based approach.

Despite bearing valuable recyclable elements, mine tailings pose environmental risks. However, there is a lack of studies on the geochemical characteristics of tailings in China and abroad, hindering their appropriate treatment and reuse. This study collected tailing samples from the Han-Xing Iron deposit in Hebei Province, China and conducted the analysis and tests of these samples. This study determined the concentrations and chemical speciation (i.e., exchangeable, carbonate-bound, Fe-Mn oxide-bound, organic-bound, and residual forms) of elements including Fe, Co, S, Cu, and Zn in tailing particles with varying grain sizes. Accordingly, it explored the implications for the exploitation and utilization of tailing resources, along with the assessment of environmental risks. This study provides deeper insights into the geochemical characteristics of tailings, producing positive impacts on the exploitation and utilization of tailing resources, as well as the prevention of environmental risks.

Effectively identifying the stratigraphic and landslide structures in landslide-prone areas is significant for disaster prevention and mitigation. By investigating the landslides in the Xuelang Mountain scenic spot in Wuxi, this study analyzed the differences between two-and three-dimensional inversion using the high-density resistivity method. Accordingly, this study explored methods for eliminating the banded effect in the three-dimensional inversion, performed three-dimensional resistivity inversion under the constraints of high-precision surface elevation data and borehole-derived prior information, and constructed a three-dimensional geological model for the study area. The results indicate that three-dimensional resistivity inversion enjoys distinct advantages in complex landslide surveys. The banded effect can be effectively suppressed by optimizing the grid spacing, damping coefficient, and filter parameters for inversion. Furthermore, the terrain-induced impacts and the multiplicity of solutions of the inversion can be significantly reduced using constraints of refined terrain data and prior information, thus improving the resolutions of stratigraphic boundaries and landslide structures. Through three-dimensional resistivity inversion and geological modeling, this study determined the three-dimensional stratigraphic structure, along with the spatial distributions of the landslide bodies and sliding surfaces, and investigated landslide mechanisms, providing important data for the survey and control of landslides in the study area.

The spectra of high-order pseudo-random electromagnetic signals encompass all the frequencies required for exploration engineering, it has the characteristics of enhancing work efficiency and strong anti-interference capability, and has been applied in electromagnetic exploration in urban environments. This study extracted effective information from high-order pseudo-random signals in the electromagnetic survey conducted in areas with strong powerline interference within the special exploration area of the Phase I engineering of the Jinan Urban Rail Transit Line 8. To efficiently extract high-quality effective information, an envelope assessment algorithm was combined with high-order pseudo-random signals. Specifically, the actual signal interference was accurately estimated by analyzing the spectral envelope values. This allows for screening received signals, thus further mitigating the impacts of powerline interference and its harmonics. As a result, more effective frequency and geoelectric information were obtained, providing abundant effective electromagnetic data for subsequent inversion and interpretation. The novel method serves as a technique for effective information extraction for future electromagnetic sounding in a complex urban environment.

Small- and micro-scale faults fractures (fractures and faults with fault throw less than 10 m) that originally developed in shale strata have a significant impact on the probability of penetration, stimulation volume, and production capacity of high-quality reservoirs in horizontal well sections. Therefore, it is critical to conduct fine-scale fault and fracture prediction. However, any single method struggles to accurately identify and predict these faults and fractures. Based on the developmental conditions of small-and micro-scale faults and fractures in the shale gas reservoirs of the Longmaxi Formation in the southern Sichuan Basin, this study conducted forward modeling, response mechanism analysis, and characterization of fracture responses, developing a prediction method integrating predicting and modeling. Furthermore, this study preferentially investigated techniques including seismic data processing, small-scale fault and fracture prediction, multi-scale fracture modeling, and fusion characterization. The results of the proposed method were highly consistent with the geological anomalies including small and micro-scale faults, lost circulation, and inter-well pressure channeling observed during the drilling of horizontal wells in the shale gas reservoirs of the Longmaxi Formation. Furthermore, these results exhibit a strong positive correlation with the single-well production capacity. All these corroborate that it is feasible to use this method to predict small- and micro-scale faults and fractures. This study can serve as a reference for predicting small-scale faults and fractures in other strata of the same type.

Conventional inversion and forward modeling of large-scale potential field data from gravity and magnetic exploration, demanding high computer performance, exhibit low efficiency. Hence, this study defined a footprint determination method for potential fields, analyzed the influencing factors, and innovatively proposed a footprint-FFT strategy for forward modeling of potential fields. The footprint-FFT algorithm improved the forward modeling process from three aspects: (1) Kernel matrices were calculated based on the potential field-derived properties, significantly reducing their size; (2) A footprint concept for potential fields was introduced and defined, decoupling data scales from kernel matrix sizes, thus improving the kernel matrix computing efficiency and reducing the hardware cost; (3) Based on the above, the computing area was divided into subspaces, and the footprint-FFT strategy was first proposed for the batch computing of potential fields in subspaces, accelerating the forward modeling process. By reducing the computational complexity and storage of the kernel matrix, the method proposed in this study significantly improved the operational speed while ensuring computational accuracy. This method enabled the fast forward modeling of potential fields with more than 1 billion grids on a laptop computer within a few minutes. Theoretical examples demonstrate that this method has high efficiency and moderate requirements for computer configuration, manifesting considerable potential in the forward modeling and inversion of large-scale potential field data.

This study aims to enhance the measurement accuracy of the electric field by reducing the range shifting and background noise of electric field sensors in the electromagnetic detection system. First, it ascertained the design requirements of electric field sensors by investigating the mechanisms of the range drift and background noise. Second, it established the Ag-AgCl-based preparation process for graphene-based stable electrolyte gel. Third, it optimized the multi-cell multi-contactor electrode structure based on polymeric microporous membranes. Finally, it developed a graphene-based electric field sensor characterized by low range drift and background noise. This sensor can retard internal ion diffusion by leveraging the ion retention ability of graphene and the multi-cell structure composed of reaction, transition, and buffer zones. Consequently, the range drift caused by changes in the ion concentration is reduced. The internal and contact resistance of this sensor can be reduced through the conductive ability of graphene and the enhanced contact with the ground via multiple contactors, respectively, thereby reducing the sensor's background noise. The graphene-based electric field sensor developed in this study shows range drift not exceeding 20 μV/24 h, and background noise not above 25 nV/√Hz. This sensor was applied to a 24 h field magnetotelluric sounding test conducted in the Duobaoshan area, Heilongjiang Province, yielding high-quality electric field data in the frequency band of 0.000 125~320 Hz, with the apparent resistivity phase curve aligning with the result of commercial electrodes. Therefore, the graphene-based electric field sensor proves effective in fieldwork.

As an important part of gravity investigation, the performance tests of gravimeters are required throughout field surveys. In these tests, mean squared error (MSE), accuracy, and root mean squared error (RMSE) are commonly employedto quantitatively describe the test results. The comparison of the theoretical equations for dynamic and consistency tests in specifications on geological surveys, petroleum, and measurement reveals a pronounced confusion in the usage of MSE, accuracy, and RMSE. This issue is observed in the consistent equations forconsistency testsin these specifications. Through investigations into the equations used in the dynamic and consistency tests inthe threespecifications, this study analyzed the differences between mean MSE and RMSE, elucidated the normativity of RMSE relative to MSE, and determined the applicablerange of RMSE. To avoid confusion, it is recommended that accuracy be used for qualitative expression and RMSE for quantitative expression in these specifications.

The inversion of petrophysical data can image the microscopic fracture structures inside rocks, revealing the evolutionary patterns of fractures within rocks and soil with changes in external environments. Hence, it is an intuitive and reliable method for investigating the mechanisms of deep geotechnical disasters. This study presented a petrophysical data acquisition system and resistivity-based forward modeling and inversion algorithms. Based on the above, this study conducted numerical simulations of 2D and 3D inversion imaging of petrophysical data. As indicated by the numerical simulation results, 2D inversion imaging can characterize millimeter-scale rock fractures with high/low resistivities, whereas 3D inversion imaging can accurately locate and effectively identify millimeter-scale fractures and vugs with high/low resistivities. Moreover, data measurement and inversion imaging were conducted on rock samples subjected to microwave-induced fracturing in three states: heated sandstone before failure, sandstone heated to a molten state, and molten sandstone in a cooled state, preliminarily revealing the variation patterns of sandstone fractures under microwave heating. Overall, this study provides a novel method for exploring the mechanisms of deep geotechnical disasters.

In actual exploration, the surface-to-borehole transient electromagnetic (TEM) method is prone to be affected by irregular transmitter loops and inclined boreholes, resulting in increased measurement errors of the three-component induced magnetic fields and decreased interpretation accuracy. By establishing surface-to-borehole TEM method-based three-component measurement models under the excitement of transmitter loops of various shapes, this study derived the calculation formulas for surface-to-borehole TEM responses under inclined boreholes through coordinate transformation. Then, it achieved one-dimensional forward modeling of the full-space TEM field using a numerical filtering algorithm. The calculation results of multiple typical models indicate that the three components of the transient magnetic fields were significantly influenced by the shapes of the transmitter loops, with the impacts on horizontal components x and y far more significant than those on vertical component z. The transmitter loops of regular polygons with even edges as the sources exhibited uniform and symmetric distribution of the TEM fields of the three components. Under the condition of the same perimeter, a greater number of edges of the transmitter loops associated with greater primary field energy excited by the loops. Therefore, rectangular transmitter loops as the sources prove the most cost-effective. The inclination and offset primarily affected the amplitude of the three-component responses. In contrast, the borehole azimuth mainly influenced the sign of the horizontal components, bearing rich information on location. Therefore, in the exploration using the surface-to-borehole TEM method, it is necessary to accurately determine source paths and the geometric morphologies of boreholes to make essential corrections, thus improving the accuracy and reliability of interpretations.

To improve the inversion accuracy of reservoirs in the Paleogene strata with limited wells and sedimentary and structural complexity, two key technologies were used in seismic data processing: sparse pulse inversion for primary wave estimation and anisotropic Q-pre-stack depth migration (PSDM). This contributed to improved quality of seismic gathers and imaging. Then, the pre-stack simultaneous inversion method was applied as follows: (1) Stacking velocity and layer-constrained Dix inversion were employed to obtain a low-frequency model of P-wave impedance; (2) Elastic impedance inversion was performed using angle-stacked data and well-calibrated wavelets, yielding far, medium, and near elastic impedance; (3) Initial P- and S-wave impedance, as well as initial density, were obtained through Fatti inversion; (4) Pre-stack simultaneous inversion was performed to obtain the final P- and S-wave impedance and density; (5) Lithology and physical property inversion results were used to predict the reservoir distribution range. This method, driven by three-dimensional seismic data and exhibiting low dependence on logs, can serve as a reference for reservoir prediction under similar geological settings.

Survey grid layout is a preliminary task of geophysical and geochemical exploration. The widespread use of handheld GPS has greatly facilitated navigation and positioning in small-to medium-scale geophysical and geochemical field surveys. This study, based on coordinate transformation theory, presented a method for generating large numbers of GPS waypoints for both regular and irregular survey grids for geophysical and geochemical exploration. Furthermore, an associated software program was developed. The software enjoys simple interfaces and convenient operations, enabling the quick generation of survey grids suitable for applications such as gravity, magnetic, and resistivity surveys, soil surveys, and stream sediment surveys. Therefore, this software can be used for field navigation.

Ray tracing-based first-arrival traveltime tomography is widely used to construct near-surface velocity models to achieve the static correction of seismic data from complex near surface.However,this method necessitates the calculation of ray paths for first-arrival traveltimes and the iterative updating of initial velocity models.As a result,significant computational time is required when applying this method to measured 3D high-density seismic data.To address this issue,this study proposed a method for quickly building 3D near-surface velocity models utilizing diving wave traveltimes under rugged surface.Specifically,based on the ray and traveltime equations of diving waves corresponding to velocities subjected to lateral and vertical changes under rugged surface,the velocity distribution from the observation surface downward was determined using common offset gathers.The proposed method eliminates the need for ray tracing and iterative updates of initial velocity models,offering high modeling efficiency.Tests based on data from theoretical models verified the effectiveness of the proposed method.When applied to measured 3D seismic data,the proposed method yielded static correction results comparable to those obtained using the Fresnel-volume first-arrival traveltime tomography while significantly improving computational efficiency.

Soil carbon pools constitute a crucial part of global terrestrial carbon pools. Hence, investigating soil carbon pools is critical for understanding the global carbon cycle and changes. Based on the soil carbon data obtained from a multi-purpose regional geochemical survey, this study estimated the densities and stocks of organic and inorganic carbon of soil at depths ranging from 0 to 20 cm, 0 to 100 cm, and 0 to 180 cm in oases on the northern margin of the Tarim Basin. Moreover, it delved into the spatial distribution of carbon density. The results of this study are as follows: (1) The compositions of soil carbon pools varied with the soil depth in the study area. At depths ranging from 0 to 20 cm, the organic carbon stocks accounted for 20.66% of the total carbon stocks. With an increase in soil depth, the organic carbon stocks gradually decreased, while the inorganic carbon stocks gradually increased. At depths ranging from 0 to 180 cm, the inorganic carbon stocks represented 85.73% of the total, suggesting that inorganic carbon predominated in the compositions of soil carbon pools; (2) The soil in three depth ranges exhibited organic carbon densities of 1,956.45, 7,913.37, and 119,73.19 t/km², which were all below the national average level, and inorganic carbon densities of 71,722.84, 37,605.54, and 71,914.93 t/km²; (3) The compositions of soil carbon pools varied somewhat across statistical units. In terms of soil types and land use types, the densities of organic and inorganic carbon were higher in fluvo-aquic soil, brown calcic soil, irrigation-silting soil, and solonchak but lower in aeolian sandy soil and irrigated desert soil. Cultivated land exhibited the highest densities of organic and inorganic carbon in the soil, whereas unused and construction land manifested the lowest carbon densities; (4) In terms of topography, undulating mountains manifested the highest soil organic carbon density, whereas alluvial-proluvial plains displayed relatively high inorganic carbon density; (5) The spatial distribution of soil carbon density in the study area was characterized by high organic carbon densities in the Yanqi Basin, medium organic carbon densities in part of Kashgar Delta (western and southern localities and eastern margin), and high inorganic carbon densities in the Aksu area. Overall, under the background of extreme drought, the oases on the northern margin of the Tarim Basin show high potential for inorganic carbon sink, with soil carbon sequestration significantly influenced by soil types, land use types, and geomorphologic landscapes.