The edge depth of geological body plays a crucial role in the semi-quantitative interpretation of gravity and magnetic potential field exploration. At present, the main inversion methods of geological body edge depth mainly include Werner deconvolution method, analytical signal amplitude method, local wave number method, Tilt-depth method, Euler deconvolution method and curvature attribute inversion method. These methods all have problems of solution selection, stability and adaptability. This paper mainly studies the adaptability of different types of data and models. Through basic principle analysis and model test, the results show that Werner deconvolution method and Euler deconvolution method are applicable to the most types of data sources, followed by curvature attribute, and Tilt-depth is the least; Werner deconvolution method, Euler deconvolution method and curvature attribute methods can adapt to many models, the Tilt-depth is least. For gravity data, the analytical signal amplitude of the first vertical derivative as the data source is applicable to all methods. For magnetic data, the analytical signal amplitude as data source is applicable to all methods. At the same time, it is suggested that other scholars should follow the following principles when using these methods to invert the edge depth of the two-dimensional body: It is recommended that Werner deconvolution is preferred, followed by curvature attribute and Euler deconvolution. The gravity data source of Werner deconvolution method and Euler deconvolution method is recommended to use the horizontal derivative of the first vertical derivative, and the magnetic data source is recommended to use the horizontal derivative. The gravity data source of curvature attribute method is recommended to use the analytical signal amplitude of the first vertical derivative, and the magnetic data source is recommended to use the analytical signal amplitude. In addition, based on the above research conclusions, some suggestions on the future research directions of the solution screening, stability and adaptability of the edge depth inversion are given.

This study summarized the progress and major application performance of gravity and magnetic techniques for onshore hydrocarbon exploration in China in recent years.By combining the research results of the authors,this study elucidated the new progress made in the gravity and magnetic techniques for hydrocarbon exploration from the prospect of acquisition,processing,interpretation,and application and sorted the application performance of these techniques in key fields including deep targets,complex areas,and volcanic rocks.Moreover,this study future analyzed the demand for the gravity and magnetic techniques for hydrocarbon exploration.By combining the new trends of gravity and magnetic exploration techniques at home and abroad,this study proposed the development direction and application prospect of gravity and magnetic techniques for oil and gas in deep strata and igneous rocks in complex areas.The results of this study show that significant progress has been made in gravity and magnetic exploration techniques,which play an important role in supporting the current hydrocarbon exploration.It is expected to develop high-precision and high-density gravity and magnetic exploration techniques and gravity-gravity-electricity-seismic collaborative innovation techniques.

Regularized joint inversion based on Gramian constraints is a hot research topic in the field of geophysical joint inversion. Given the difficulty in selecting weighted factors of the regularization and constraint items, it is necessary to introduce inequality constraints into the regularized joint inversion. To investigate the regularized joint inversion of magnetotelluric (MT) and gravity data based on Gramian constraints, this study compared the application effects of the penalty function method and the transform function method in the joint inversion and processed the measured data of a survey line in Xiangshan, Jiangxi Province. According to the results from model experiments, both methods can effectively constrain petrophysical parameters, and the penalty function method has higher flexibility but requires the artificial setting of the weighted factors. Moreover, the processing of the measured data shows that the joint inversion based on inequality and Gramian constraints is highly practical and can improve the precision of geophysical interpretation.

The Bohai Basin has the most offshore oil and gas fields discovered in China. As a potential hydrocarbon-rich sag in the Bohai Basin, the Qinnan Sag is of high value in exploration. Therefore, the study of the tectonic framework of the sag and its adjacent areas is of great significance and application value. Based on satellite gravity anomalies, this study determined the Bouguer gravity anomalies by correcting the influences of land topography and seawater and obtained the planar distribution and apparent depths of faults, the thickness of Cenozoic strata, and the boundaries of tectonic units using methods such as the normalized vertical derivative of the total horizontal derivative (NVDR-THDR), the Euler deconvolution, the minimum curvature potential field separation, and the fast for the gravity field based in a dual interface model. Based on the geological and geophysical data, this study analyzed the distribution and geophysical characteristics of major faults and tectonic units in the study area. The results of this study are as follows: The faults in the Qinnan Sag and its adjacent areas mainly have NE, NEE, and NW strikes and an apparent depth of primarily 1~10 km, which is up to 15~25 km at some positions of the sag-controlling faults and the intersections of the faults; The Cenozoic strata have a thickness of 0~11 km. The Cenozoic tectonic units are distributed in alternating NE and NEE directions, and their boundaries are mostly controlled by faults; Through further investigation, this study classified the sub-sag on the west side of the Qinnan sag as the Laoting sag and adjusted the boundaries of other tectonic units. The results of this study on the distribution of the faults and tectonic units can provide geophysical data for hydrocarbon exploration in the Qinnan Sag.

To remove the effect of terrain mass on observed gravity values, it is necessary to conduct terrain correction in gravity exploration. Terrains have the greatest impact on gravity values because they are the closest to observation points. However, the complex topographic relief makes it difficult to precisely determine the variation of topographic relief. Therefore, terrain correction is the most critical factor in the improvement of the precision of gravity exploration. The grid size of terrain data and the terrain correction radius are the key factors affecting the calculation precision of terrain correction. This study collected the DEM data with resolutions of 5 m, 10 m, 25 m, 50 m, and 100 m for plains, hills, and mountains. Based on these data, this study calculated conventional and generalized terrain correction values under different grid spacings and correction ranges and analyzed the influence of different grid spacings and correction radii on terrain correction in gravity exploration. The results are as follows: the gravity effect of the terrain mass above the geoid on the observation points was mainly concentrated in the range of 0~5 000 m and accounted for about 90% of the influence value of the total terrain mass. Attention should be paid to the correction of the middle and far areas during the terrain correction of hills and mountains, and it is necessary to appropriately increase the correction range of the middle areas; Different types of terrains had different requirements for grid spacings, and greater variations in topographic relief imposed higher requirements for the resolution DEM data. Based on the results of the comparative analysis, this study proposed some suggestions on the selection of DEM grid spacings and correction radii for different types of terrains. This study provides an important reference for the theoretical study and specification refinement of gravity terrain correction and has a great prospect for applications.

The Luoning area is located at the junction of the Xiaoshan Uplift and the Luoning Basin and falls into the Quaternary shallow overburden area. Large-scale silver-lead-zinc deposits such as Laoliwan and Zhonghe have been discovered in this area, and their formation is closely related to the acidic plutons controlled by fault structures. This study investigated the distribution of fault structures and acidic plutons based on the processing of 1:50000 gravity and magnetic data using the minimum curvature potential field separation technique, the normalized vertical derivative of the total horizontal derivative (NVDR-THDR) technique, the correlation analysis method, and the three-dimensional physical property inversion. The study results are as follows: (1) The Luoning area is affected by the NW-, NE-, and EW-trending structures; (2) Centering on the Laoliwan area, multiple sets of faults present a ring-shaped distribution with a radius of 6.5 km; (3) Multiple concealed plutons were discovered, and the boundaries of Laoliwan and Zhonghe plutons were re-determined; (4) The distribution of granites is controlled by ring-shaped structures and have a burial depth of about 3 km; (4) The ring-shaped structures are well correlated with magnetic anomaly gradient zones, where ores were found in many boreholes. Therefore, it is of great significance to carry out prospecting studies in these zones.

The western Zhen'an area enjoys superior ore-forming conditions of tungsten-molybdenum polymetallic deposits. A batch of large and medium-scale tungsten-molybdenum deposits such as Dongyang, Qipangou, Guilingou, Yueheping, and Hetaoping, have been discovered in this area, and they are related to intrusions. To explore tungsten-molybdenum ore bodies, it is necessary to carry out studies on intrusions related to mineralization, especially concealed intrusions. Based on high-precision gravity anomalies, this study extracted the gravity anomaly data of concealed plutons using the minimum curvature potential field separation method. Moreover, it investigated the plane positions of the concealed plutons in the western Zhen'an area by combining the geophysical characteristics of the exposed plutons, identifying five concealed plutons, namely Lanbandeng, Shapingcun, Yuehetai, Dongchuanjie, and Huangjinmei, through investigation. Moreover, this study conducted the 3D gravity anomaly inversion for typical concealed plutons, determining the spatial distribution characteristics of the concealed plutons. The Yuehetai and eastern Lanbandeng concealed plutons have been verified through boreholes, with high-grade wolframite being discovered. The method proposed in this study can provide technical support for the study of concealed plutons in the Zhen'an area and other areas, as well as important data for the study of the tectonic-magmatic-metallogenic evolution of the southern Qinling metallogenic belt.

As resource exploration deepens and becomes increasingly difficult,improving the imaging precision and the reservoir prediction accuracy under a complex tectonic setting has become a top priority of research.The full waveform inversion (FWI) method developed in recent years can be applied to complex geological structures.This method can reveal structural details in a complex geological setting using the dynamic and kinematic information in the pre-stack seismic wave field.However,this method involves many research elements such as model parameterization,building of inverse error function,data preprocessing,numerical simulation of wavelengths,and wavelet estimation.Thus,its development is bound to be a long-term gradual improvement process.The FWI method has been applied to actual observation data with the development of theory and computer technology.This study introduced the principle and processing flow of the FWI method and summarized its development history and its application status in marine and onshore seismic data,and deep seismic reflection data.Accordingly, this study presented the current application bottlenecks,data processing difficulties, and challenges of deep-crustal inversion imaging for subsequent research and application of the FWI method.

Laochang, Lancang, Yunnan is one of the most important polymetallic mining areas in the southern part of Sanjiang Tethys metallogenic belt. After years of mining, the shallow resources are nearly exhausted. In recent years, granite porphyry and porphyry polymetallic mineralization have been newly discovered in the deep part of the mining area, highlighting the prospecting potential of deep polymetallic deposits. In order to trace the occurrence of deep ore-controlling strata and structures in the study area and help to make a breakthrough in deep ore prospecting, high-power induced polarization method and audio magnetotelluric method were implemented to image the deep structure situated. Results obtained from the inversion of the measured induced polarization and electromagnetic data recuperated the distribution of induced polarization anomalies and the characteristics of deep electrical structure within the study area. Combined with the available regional geological settings, the main conclusions are as follows: The low resistance and high polarization anomalies in the northwest of the survey area are deeply related to the surface ferromanganese, silver manganese, and deep polymetallic mineralization, and the high resistance and high polarization anomalies in the middle and east of the survey area are in good agreement with the deep polymetallic mineralization. The upper Carboniferous limestone and dolomite strata are thick in the west and thin in the east, with the west strata dipping to SW and the east strata overlying the Yiliu Formation of the lower Carboniferous. The concealed granite porphyry dips in NE direction, and the coupling part between its deep 2 300~2 800 m horizontal section and deep fault is a favorable area for deep polymetallic mineralization. Notably, joint interpretation yielded from the high-power induced polarization method and the audio magnetotelluric method applied improved the reliability of deep polymetallic ore detection and provided more information of positioning the subsequent drilling layout.

The Qiemoge Mountain area in Tianjun County, Qinghai Province has a cold, semi-arid grassland landscape. A pegmatite belt with a width of 300~500 m and an intermittent extended length of 7 km has developed on the surface of this area. The rare Li-Be ores have been discovered during the current exploration in this area. To provide a reliable geochemical basis for the prospecting of rare metals and rare earth elements (REE) in areas with similar landscapes, this study conducted the grain-scale experiment and validity investigation in this study area using the large-scale micro-channel system geochemical survey technique. Based on the 1∶25,000 geochemical survey, grain sizes of -4~+ 20 meshes, -4~+ 40 meshes, -10~+ 40 meshes, and -10~+ 60 meshes were adopted in sampling for the experimental study in the zones bearing pegmatite veins. The contents of Cu, W, Sn, Be, Li, Nb, Rb, Zr, La, and Y were analyzed. The results show that relevant elements exhibited significant enrichment and dispersion characteristics and the geochemical distribution of these elements agreed well with the geological and mineral characteristics when grain sizes of -4~+ 40 meshes and -10~+ 40 meshes were adopted for the sampling of Be, Li, Nb, Rb, and Zr, grain sizes of -10~+ 40 meshes were adopted for the sampling of rare earth elements such as La and Y, and grain sizes of -10~+ 60 meshes were adopted for the sampling of nonferrous metal elements such as Cu, W, and Sn. The results of this study prove that the large-scale micro-channel system survey technique can obtain significant results in the geochemical prospecting of rare metals and REEs in areas with similar landscapes.

Jianchi Town of Shaanxi Province is located in the Nanjiang foreland-superimposed basin on the northern margin of the Yangtze Plate. To determine the prospecting potential, this study conducted a 1∶25,000 stream sediment survey in the study area. Based on the testing results of 12 elements and compounds closely related to mineralization, namely K₂O, Na₂O, CaO, MgO, Cl, S, B, Rb, Cs, Li, Br, and I, this study analyzed the geochemical characteristics of these elements and compounds and determined that Li is the major metallogenic element, Li-B-Rb-Cs-K₂O is the indicator element association for the prospecting of lithium deposits, and the spatial morphology of Li agrees with that of various geological bodies. By combining the metallogenic geological setting, this study delineated 18 integrated anomalies. Through the follow-up examination of the anomalies, multiple lithium ore bodies (mineralized points) were discovered, indicating that the study area has favorable metallogenic geological and geochemical conditions and great prospecting potential.

The Saima alkaline complex is a unique and complex geologic body. It is well known for its diverse rock types and mineral types and high contents of uranium, thorium, and rare and rare earth elements. This study analyzed and summarized the geological exploration results of the Saima alkaline complex area in recent years, discovering that the rocks in the second intrusive stage of the Saima alkaline complex show the wide mineralization of rare and rare earth elements, with a moderate- to low- mineralization temperature. There are mainly two types of deposits in Saima alkaline complex area, namely the residual magmatic metasomatism type and the skarn type. Furthermore, the prospecting potential of the whole alkaline complex was analyzed by combining the 1∶200,000 stream sediment survey data and the 1∶10,000 primary halo survey data. Three predicted metallogenic zones of rare earth and radioactive elements were delineated in the Saima alkaline complex and its surrounding area, namely Saima-Gujia, Aiyang, and Shuangshanzi. This study is of great significance for the prospecting of rare and rare earth polymetals in the Saima alkaline complex area.

The second member of the Xujiahe Formation (the Xu-2 Member) in the Anyue area of the Sichuan Basin enjoys abundant tight gas reserves.However,this member has complex geological characteristics,and conventional amplitude versus offset (AVO) analysis has relatively low precision in predicting the gas-bearing property of the reservoir in this member.Therefore,it is necessary to develop a more fine-scale seismic prediction method. Based on the analysis of single-well petrophysical characteristics and forward models,the AVO attributes of the dominant frequency range were selected through the frequency division AVO inversion based on wavelet transform.Then,these AVO attributes were fused to form the gas-bearing indicator,using which the distribution of favorable gas-enrichment zones in the Xu-2 Member of the Anyue area was predicted.The results are as follows:The gas zones in the Xu-2 Member primarily present class IV AVO anomalies;For the gas and water zones,their AVO responses in the dominant frequency range (35~45 Hz) differed significantly from those in the full frequency band,and their gas-bearing response characteristics were more pronounced in the dominant frequency range;The AVO attributes sensitive to the gas-bearing property included the difference in the S-wave velocity,the difference in Poisson's ratio, and the fluid factor.The gas-bearing indicator was obtained through the fusion of these AVO attributes,and the negative anomalies of the gas-bearing indicator were indicative of favorable gas-bearing zones;The seismic-log correlation shows that the AVO attributes in the dominant frequency range yielded positive gas-bearing prediction effects.The method proposed in this study is expected to provide technical support for unconventional oil and gas exploration.

The area around Maduqiao Village, Langqiao Town, Jing County has great potential for the development of high-quality mineral water. However, due to the geological conditions and the inhomogeneity of water-bearing media, the investigation of the distribution range of the mineral water in the area and the quantitative evaluation of the water quantity and quality have always been challenges to the development and utilization of mineral water in the area. With the Langqiao area of Jing County as the target area, an application study on the comprehensive geophysical prospecting method that comprehensive ground geophysical prospecting with hydrogeological logs was conducted, achieving important progress. The major results are as follows: (1) The fault structures in granodiorites were precisely located through comprehensive ground geophysical prospecting, and the horizon of tectonic fissure water was precisely identified based on hydrogeological logs; (2) The metasilicate natural mineral water for drinking with a single well water yield of 50~80 m³/d was identified; (3) The water-rich fault structures in the study area have a medium to shallow burial depths of about 75~140 m and primarily have a NW strike. These results reveal the spatial distribution characteristics of the mineral water-bearing structures in the study area and are of great significance to the subsequent investigation of the mineral water range. Moreover, the systematic research philosophy and technical methods used for the Langqiao area of Jing County in this study can guide the mineral water exploration in similar areas.

To investigate the water yield properties of the aquifers in the hanging and foot walls of coal seams under the extremely-thick low-resistivity layer, this study conducted the hydrogeological exploration using the wide-field electromagnetic method (WFEM) targeting a coal mine in the Huainan area, Anhui Province. The geological results obtained through multiple means, such as test analysis and data acquisition and interpretation, agree well with the downhole conditions. As indicated by the successful WFEM application in the hydrogeological exploration of the coal mine, the WFEM features strong penetrability, large investigation depth, and high accuracy. Therefore, the WFEM can be used as a new geophysical exploration method for the hydrological survey of large-depth coal fields.

As a karst reservoir with the highest altitude in Wenshan City,the Xiaohewei reservoir has been suffering from severe water seepage since its completion.Despite several seepage control treatments,the seepage of the reservoir is still not effectively controlled.To determine the locations of underground karst seepage pathways of the reservoir and guide the later seepage control project,this study detected the seepage pathways in the project area combining the high-density resistivity method and the audio magnetotelluric method.The 2D inversion trial calculation of geophysical testing data indicates the feasibility of combining the two methods.The methods show highly consistent geophysical anomaly positions and can accurately reflect the geological conditions at different burial depths.Thus,their detection results can be referenced for later design and construction.Based on the inversion of measured data,the surface geological data,and the drilling verification means,it is speculated that the reservoir mainly has two NNE-directed karst water-bearing seepage pathways with an elevation of more than 1 800 m.These two karst seepage pathways (No.1 and No.2) are located near the contact zone between limestones and siliceous rocks,and in the karst fissures inside limestones,respectively.Based on the geophysical exploration results,this study also puts forward some suggestions on the deployment of the curtain grouting project for later seepage control of the Xiaohewei reservoir.

To evaluate the fracturing performance of two horizontal wells of well Anye-2,this study explored the layout of the fracturing monitoring network and data acquisition and processing using the fracturing monitoring technique combined with the wide field electromagnetic method.Through the qualitative and semi-quantitative difference analysis of the pre-,in-,and post-fracturing monitoring data,this study preliminarily determined the propagation direction of induced fractures and semi-quantitatively calculated the parameters such as fracture length and height.For each fracturing interval,the parameters such as fracture height and length were quantitatively determined through fine-scale inversion with depth as constraints and difference calculation.The fracturing monitoring results show that the fractures at two horizontal wells had lengths of 100~125 m and heights of 20~25 m.The fracturing production was guided by evaluating the fracturing performance of each fracturing interval.The fracturing results of the previous interval were used to guide the fracturing of the subsequent interval.Finally,the fracturing performance of all fracturing intervals was evaluated.The application results show that the wide field electromagnetic method can effectively predict the spread direction and range(e.g.,fracture length) of fracturing fluids,achieving encouraging performance.

With more than 20 years of development, the X-ray fluorescence core scanners (XRF-CS) have been widely applied in the elemental analysis of multi-type sediment cores, the paleoenvironment reconstruction, and the exploration of mineral reservoirs and their abundance, exhibiting great potential for application. However, there is a lack of studies on the influencing factors and correction of the elemental signals output by XRF-CS (especially in China), which restricts the proper use of XRF-CS and the accurate interpretation of their data. Compared with conventional XRF techniques, XRF-CS enjoy a high processing speed (only 1/10 of the time for conventional analysis), high continuity, non-destructive scanning, and a high resolution (up to 0.02 mm). However, XRF-CS only output semi-quantitative values of elemental signals and thus fail to accurately identify the element compositions. This study summarized the influencing factors of the values of the elemental signals output by XRF-CS in terms of instruments and cores, together with the degrees of the influences. On this basis, this study proposed achieving the balance between the intensity of elemental signals output by XRF-CS and cost by selecting appropriate scanning steps and exposure time on the premise of the optimal instrument setting. This study also suggested that the influences of water content and particle sizes on elemental signals should be eliminated as far as possible by drying in the air and smoothing the core surface during the scanning. To improve the accuracy of elemental signals output by XRF-CS, this study systematically introduced three types of international common calibration models and their application potential, namely the normalized median-scaled (NMS) model, the log-ratio calibration equation (LRCE) model, the improved multivariate log-ratio calibration (MLC) model, the normalized polynomial-scaled calibration (NPS) model, and polynomial-corrected multivariate log-ratio calibration (P-MLC) model. Finally, this study proposed further enhancing research on the comparative analysis of the influence exerted by the same factor among multiple types of XRF-CS; the optimization of calibration models and development of visual software packages; the equipment of multiple sensors for integrated scanning, and the extensive applications in the exploration and evaluation of geological and mineral resources.

Given the particularity of biological samples, this study employed microwave digestion and inductively coupled plasma-optical emission spectrometry (ICP-OES) for the simultaneous determination of 12 elements in biological samples, including aluminum (Al), ferrum (Fe), magnesium (Mg), calcium (Ca), sodium (Na), potassium (K), manganese (Mn), phosphorus (P), titanium (Ti), barium (Ba), strontium (Sr), and zinc (Zn). By optimizing the pretreatment conditions of microwave digestion samples, this study selected the mixed reagent of reverse aqua regia (10 mL) and hydrogen peroxide (1 mL) as the digestion reagent, and an appropriate experimental procedure for the microwave digestion system to ensure complete decomposition of samples. Moreover, this study selected the optimal plasma excitation conditions, analytical spectral lines of elements, and background subtraction position to ensure high determination sensitivity of elements and interference-free spectral lines. This study plotted the calibration curve with the national primary reference materials for biological components as the calibration series, making the calibration series consistent with the sample matrix as much as possible. The simultaneous determination method had a total dilution multiple of 100, eliminating the interference of the matrix effect. The results show that this method had a detection limit of (0.04~4.93)×10^-6 and a relative standard deviation (RSD) of 1.41%~5.13%, showing high precision. As verified by the national primary reference materials, this method had a relative error (RE) within ±10% and determined values consistent with standard values. Therefore, this method is accurate and reliable, meeting the analysis requirements of biological samples.

The strike-slip fault system and the fractures and vugs in fault-controlled reservoirs have become new Ordovician exploration targets in the Shunbei area.This study explored a multi-attribute quantitative prediction technique for the single-well production of fault-controlled reservoirs,aiming to provide a scientific basis and technical support for well deployment and well trajectory optimization in the fault zones of the Shunbei area.Faults serve as pathways for hydrocarbon migration in fault-controlled reservoirs.Their connectivity to provenance areas can be characterized by their longitudinal extension and the width of the fault zone,and their convergence can be characterized by their lateral extension and the planar intersection structure between major and secondary faults.Both characteristics of faults were used to indicate the fault characteristics in the oil source conditions for oil accumulation.The space for hydrocarbon accumulation in fault-controlled reservoirs is dominated by dissolution fractures and vugs,such as caves.The fracture-vug characteristics,which represent the space for hydrocarbon accumulation and its connectivity,were characterized by the scale of fault-controlled reservoirs,the volume of the fractures and vugs,and the density of fractures in faults.The single-well production of fault-controlled reservoirs is related to both the fault characteristics and the fracture-vug characteristics.Therefore,the quantification of fault characteristics and the fracture-vug characteristics is the basis for the quantitative prediction of single-well production.The fault characteristic values were determined through the fine-scale interpretation of faults based on seismic data and their multiple attributes.Moreover,the range of fault-controlled reservoirs was delineated based on structure tensors;the distribution and volume of caves,fractures,and vugs were characterized using the amplitude of anomalous bodies;and the density of fractures in faults can be characterized using the maximum likelihood probability.Then,the three attributes were fused to determine the fracture-vug characteristic values.Finally,the quantified fault characteristic values and fractured-vug characteristic values were fused into the characteristic value of fault-controlled reservoirs.Through the statistical analysis of the characteristic value and annual liquid production of drilled wells,the statistical relationship between the annual fluid production and the characteristic value of fault-controlled reservoirs was determined,thus achieving the quantitative prediction of the single-well production of fault-controlled reservoirs.

In marine seismic exploration,seismic reflection characteristics play an important role in AVO analysis,inversion for seabed parameters,and structural analysis.When seismic waves propagate in the ocean,their seismic reflection characteristics are affected by the seawater layer and the sediments beneath the seabed.However,previous studies mainly focus on the influence of the sediments beneath the seabed,while there is a lack of studies on the effects of the seawater layer on the seismic reflection characteristics.This study analyzed the changes in the seismic wave field during the seismic wave propagation in the seawater layer.Based on the boundary conditions of fluid-solid and free interfaces,this study derived the P-P amplitude ratio between the incident and reflected waves on an elastic interface and obtained the mathematical expression of the seawater layer effect accordingly.Then,this study analyzed the influencing factors,such as the frequency of incident waves,the depth of the seawater layer,the impedance contrast of the seabed,and the incident angle,on the filtering effect of the seawater layer.The analysis results are as follows:The seawater layer had a periodic frequency selective filtering effect on seismic P-waves;The period of the frequency selective filtering effect was inversely proportional to the frequency of incident waves and the depth of the seawater layer and was directly proportional to the incident angle;A higher incident angle corresponded to severer attenuation of seismic P-waves;The effects of impedance contrast on amplitude was related to the frequency of incident waves and the depth of the seawater layer.Finally,the study verified the effects of the seawater layer on seismic reflection characteristics through numerical simulations.

Terrestrial heat flow has a high reference value for the evaluation of geothermal resources since it can directly indicate the Earth's internal heat on the surface.However,no high-quality and high-resolution terrestrial heat flow measurements have been conducted in the Songliao Basin due to costly and difficult conventional heat flow measurements based on the drilling technology.Machine learning,as a technology for data analysis,can identify patterns in data and utilize these patterns to automatically calculate unknown data.This study calculated the regional terrestrial heat flow using the machine learning method.Based on the measured data of global terrestrial heat flow and the geological structure data,both the Kriging regression algorithm and the machine learning algorithm were used to calculate the terrestrial heat flow in a known heat flow distribution area,as well as the root mean square error and the correlation coefficient.The machine learning algorithm yielded results with a smaller error and a higher correlation.Then,the terrestrial heat flow in the Songliao Basin was calculated using the machine learning method.As revealed by the calculation results,the terrestrial heat flow is the highest (more than 80 mWm^-2) in the Songliao basin and gradually decreases outward in a circular pattern centered on the area between Daqing and Songyuan.The results are highly consistent with the measured results of the regional geothermal gradient,providing a reference for further analysis of the distribution patterns of geothermal resources in the Songliao Basin.Finally,the sensitivity of geological characteristics was analyzed using the Sobol method to quantify the effects of various parameters.This study verifies that the machine learning method has a high research and application value in the calculation of terrestrial heat flow.

As shown by the geochemical survey of national land quality, the land with excess fluorine in China covers an area of about 315 000 km². As an element closely related to human health, fluorine has received wide attention and has been studied. Especially in recent years, the high-fluorine fertilizers used in agricultural activities have become a potential source of fluorine in soils. Moreover, the circulation and migration patterns of fluorine in soils, animals, and plants are yet to be further investigated. To prepare for a new round of national soil survey and modern health-related geological survey, it is necessary to develop a method to accurately determine the fluorine content in chemical fertilizers. Through experiments, this study compared four methods for sample decomposition, namely the extraction methods based on HCl boiling, NaOH molten water, and the Na₂O₂ molten water and the HCl ultrasonic extraction method at room temperature. The results show that the optimal method for sample pretreatment is to extract and decompose samples using ultrasound and HCl at room temperature, adjust the acidity using NaOH-H₂SO₄, and take sodium citrate as the ion buffering agent. Through investigation, the ultrasonic extraction time and temperature were determined to be 20 min and 20 ℃, respectively. The main quality parameters of the method were determined under the optimal sample pretreatment conditions, including the limit of detection of 1.63×10^-6, the precision of 0.98%, and the recovery rate of 91%~108%. The results of this study show that the pretreatment of this method is simple, fast, and easy to operate. With the mode of establishing standard curves in sections, the quality parameters determined can fully meet the requirements for the analysis of chemical fertilizers.

Studying the occurrence of natural gas hydrates (NGHs) is of profound significance for NGH exploration. The evaluation of the NGH saturation mainly relies on the Archie equation using the electrical parameters of rocks. The key to accurately calculating the NGH saturation is to select corresponding values of rock electrical parameters for different geological environments, especially the porosity index (m) and the saturation index (n). However, it is still a challenge to select the optimal m and n values for NGH evaluation in resistivity logging. To ascertain the relevant resistivity regularity of NGHs and the determination method of rock electrical parameter values in the Archie equation, this study systematically reviewed relevant references and summarized the resistivity influencing factors of NGHs. Moreover, this study analyzed the influencing factors for the accurate evaluation of the NGH saturation based on the Archie equation. Accordingly, this study generalized the resistivity characteristics of NGH-bearing sediments and proposed the application research direction of the Archie equation.

As an important part of urban infrastructure, underground water supply pipelines frequently leak or break due to disrepair,corrosion,and poor construction quality.It is of great significance to identify the leakage locations and affected areas of underground water supply pipelines using a non-destructive testing method for the purpose of early warning and follow-up treatment.This study conducted simulated detection experiments and analysis of underground water supply pipeline leakage using the ground penetrating radar (GPR) method.Firstly,this study established the leakage model of water supply pipelines in sandy soil using the SEEP/W module in the GeoStudio software and calculated the volumetric water content of different leakage locations and leakage times.Then,it established the relative dielectric constant and conductivity model for water supply pipeline leakage using the Topp equation and the empirical equations of electrical conductivity and water content.On this basis,this study conducted the GPR simulated detection of the water supply pipeline leakage model with different leakage locations and different leakage times using the finite difference time domain (FDTD) method and analyzed the simulation results.Finally,this study conducted the GPR-based physical simulated detection tests of water supply pipeline leakage and compared the test results with the numerical simulation results.The study results are as follows.Compared with the hyperbolic diffracted wave of the water supply pipelines without leakage,that of the water supply pipelines with leakage at different locations are stated as follows.For the leakage on the upper side,a longer leakage area and a larger leakage area were associated with an earlier present hyperbolic diffracted wave with weaker energy,while the horizontal position of the hyperbolic diffracted wave's vertex remained unchanged.For the leakage on the lower side,two hyperbolic diffracted waves appeared,which moved up and down individually.Moreover,a longer leakage time corresponded to two weaker and more separated hyperbolic diffracted waves.The horizontal positions of the hyperbolic diffracted waves' vertexes remained unchanged.For the leakage on the left (right) side,a longer leakage time was associated with a weaker hyperbolic diffracted wave,whose vertex deviated farther toward the upper left (right).The simulated detection results of this study can provide a reliable basis for early warning and follow-up treatment of water supply pipeline leakage.

With the rapid development of the economy and society,traffic loads have increased sharply,gradually causing a series of pavement diseases.Ground penetrating radar (GPR),which is a non-destructive testing technique,can present the echo information of subsurface targets on the GPR profile.The echo information of diseases,such as voids,cavities underneath the pavement,and loosely infilled voids,constitutes a region of interest(ROI) on the GPR profile.The traditional manual ROI extraction method features high technical requirements and high laborious intensity due to massive data.Therefore,this study proposed an automatic ROI extraction method that combines the threshold segmentation data and the row-column variance.The experimental results show that the method proposed in this study can effectively extract the location information of multi-type and multi-target ROIs.This method has great potential for improving road detection efficiency based on GPR.

Existing log modeling methods fail to consider the directionality of geological deposition, yielding low modeling precision.To overcome this obstacle,this study proposed an inverse-distance weighted (IDW) modeling method under logging azimuth occlusion by analyzing the advantages and disadvantages of the IDW log modeling method.The new method proposed in this study adopted the IDW interpolation formula under azimuth occlusion.In addition to the influencing factors of the distance between known information points and interpolation points,the new method also considered the azimuth occlusion between known information points.Moreover,this study quantitatively described the influence of azimuth occlusion between known samples by integrating the weighting coefficients of non-azimuth occlusion.As indicated by the comparison between the new method and conventional methods based on numerical experiments and actual data,the modeling results of the new method showed gentler and more natural spatial variation,which conformed to the variation patterns of geological deposition.In sum,the method proposed in this study reflects the spatial continuity and directionality of geological deposition,has distinct advantages in improving the precision of geological log modeling,and thus can be widely applied to practical applications.

To investigate and assess the characteristics of cadmium, lead, and zinc in the soil and crops in the farmland around the old industrial area in the south of Baotou City, this study analyzed and tested the heavy metal content in soil, crop root soil, and seeds, assess the pollution according to relevant standards, and conducted the risk assessment and source analysis of heavy metals using the pollution index, the bioconcentration factor, and human health risk index. The results are as follows:Regarding the soil environmental quality, the soils in the study area are dominated by clean soils, with the polluted soils distributed primarily on both sides of the old sewage canals.The sites of over-limit root soils are also primarily distributed around the old sewage canals.Among the heavy metal morphologies, carbonate-bound, Fe-Mn-bound, and residue heavy metals account for relatively high proportions, while exchangeable heavy metals (water-soluble and ion-exchange) account for relatively low proportions. Most of the seed samples exhibited normal and low enrichment of heavy metals. Compared with other crops, sunflower seeds showed super adsorptivity of cadmium, lead, and zinc, posing significant non-carcinogenic and carcinogenic health risks to children and adults.

This study sampled the soil and the corresponding roots, stems, and leaves (including large leaves, new leaves, and sprouts) of tea plants from three ecological tea plantations in Qiongzhong County, Hainan Province. Based on these samples, this study investigated the migration of heavy metals in the soil-tea plant system and analyzed the migration patterns of heavy metals and the health risks caused by heavy metals in tea. As indicated by the results, the Pb, Cr, Cd, As, and Hg concentrations in the soil are slightly higher than the background values of corresponding soil elements in Hainan, showing non-significant accumulation. The enrichment of heavy metals varies significantly in different organs of tea plants. Specifically, Cr, Zn, Pb, Hg, and Cd are enriched in roots, while Cu and Ni are enriched in leaves; Pb, Cd, and Hg have higher concentrations in large leaves than in new leaves and sprouts, indicating that these elements are enriched with the growth of leaves; Cu, Ni, and Zn have higher concentrations in sprouts than in leaves, showing that these elements are enriched in the growing parts of leaves. Bio-concentration factors (BCF) indicate that soil physicochemical composition, heavy metal species, and leaf age have effects on the absorption of heavy metals by tea leaves. The results of the risk assessment show that the target hazard quotients (HQ) and hazard indices (HI) of all samples are less than 1, indicating acceptable health risks caused by heavy metals in tea. This study can provide a scientific basis for the prevention and control of heavy metals in tea plantations and has a positive guiding significance for managing tea plantations and ensuring the health of tea consumers.

Vanadium (V) is an essential trace element required by organisms for maintaining their normal life activities. It is also a harmful element listed as a priority environmental pollutant by the United Nations Environment Programme (UNEP). The study of the migration and enrichment patterns of V in the soil and plant system is of great practical significance for further understanding the ecological geochemical behavior of V and ensuring the safety of agricultural products and human health. This study systematically sampled the soil and plants in some ordinary farmland in Linyi City, Shandong Province and analyzed and tested the contents of V and its associated elements in the soil and plant samples. Moreover, this study conducted the source analysis and pollution assessment of V and investigated the migration and transformation patterns of V in the soil-plant system using statistical methods such as descriptive statistics, correlation analysis, and cluster analysis, as well as the single factor pollution index method, the potential ecological risk index method, and the biological enrichment coefficient method. The results are as follows: V is relatively concentrated in the study area, and its content increases with an increase in the Fe and Ti contents and decreases with an increase in the SiO₂, Na₂O, Sr, and CaO contents; The V in the study area mainly originates from the weathering of parent rocks, and the parts with a high V content is related to magnetite; As shown by the results of the single factor index method and the potential ecological risk index method, V is relatively clean in the soils of the study area, but attention should be paid to the pollution of the associated Cd; V is enriched primarily in the roots of plants, and plants' absorption capacity of V is generally negatively correlated with the contents of Cu, Pb, Zn, Ni, Co, Cd, and especially Cr in soils and is positively correlated with the As content in soils. This study enriches the ecological geochemical theory of V and provides a scientific basis for regional agricultural production, environmental quality assessment, and ecological pollution control.