The heavy metal element contents in soil affect the quality of soil environment. Their prediction using different models based on survey data is an important means to study the changing trends of soil element contents and soil environmental quality. Based on the data from 1∶250 000 multi-purpose regional geochemical surveys and 1∶50 000 land quality geochemical assessments, this study predicted the contents of five heavy metal elements in the soil of the study area in 2027 using the single-period incremental model and the input-output flux model individually. The results are as follows. The two models yielded different prediction results but consistent trends that the contents of five heavy metal elements increased to different degrees. Moreover, the single-period incremental model yielded larger increments than the input-output flux model. Among the various input channels of the flux model, Cd and Pb entered the soil mainly through dry and wet atmospheric subsidence, As and Cr entered the soil mainly through fertilization, and Hg entered the soil mainly through irrigation water. Based on the survey and prediction data of soil monitoring sites, the soil environmental quality grade was classified for these sites. The proportion of the sites for priority protection showed a downward trend, indicating that the soil environmental quality decreased year by year.

The copper mineralized bodies and orebodies of the Pulang copper deposit in Yunnan Province are mainly distributed in the Pulang complex porphyry body and were formed through complex multi-stage development. This study aims to detail the geophysical response and fractures of copper reservoirs and provide detailed orebody characteristics, fractures, and horizon burial depth to be referenced in the exploration and exploitation of the Pulang copper deposit. First, the borehole-log data in the Pulang copper deposit were sampled for comprehensive evaluation. Then, in combination with the drilling reports and data on partial core samples, this study analyzed the log response characteristics and fractures and identified the lithology of the Pulang copper deposit using mathematical statistics, three-dimensional cross plots, convolutional neural networks (CNNs), and fracture parameter calculation. The log response characteristics of the three major strata of quartz monzonite porphyries, quartz diorite porphyrites, and hornstones in the study area are as follows. The hornstone strata have relatively high resistivity, followed by the quartz diorite porphyrite strata and the quartz monzonite porphyry strata in sequence. The resistivity decreases significantly at the intervals with fractures occurring or at the relatively fractured intervals. The quartz monzonite porphyry strata have a relatively high charge rate (polarization rate) of up to about 10%. The hornstone strata have relatively high radioactive intensity than the quartz diorite porphyrite strata and the quartz monzonite porphyry strata. CNNs were used to identify and analyze the lithology of the three major types of strata based on log data, with an accuracy rate of 97.94%. Finally, this study identified fractures in these strata using dual laterolog data. The resistivity significantly decreases at intervals with fractures occurring and differs greatly between deep and shallow lateral resistivity. The quartz monzonite porphyry strata with a high copper grade have relatively low resistivity and relatively well-developed high-angle fractures. The results of this study are of significance for the identification of ore body characteristics and the exploitation of ore bodies in the Pulang copper deposit.

The ultradeep Ordovician limestone fracture-vug reservoirs in the Fuman oilfield on the south bank of the Tahe River in the Tarim Basin is the core target area for the production capacity construction of the oilfield.These reservoirs in the study area contain massive dissolution vugs formed by the formation fracturing due to the strike-slip faulting and thus are highly heterogeneous.The low-frequency models based on conventional wave impedance inversion are built using data on horizons,faults,and logs,and thus they cannot characterize the fault-controlled heterogeneity of the reservoirs.For this reason,this study proposed an iterative inversion method constrained by fault fractured zone facies to predict reservoirs.The technical process of this method is as follows.First,the original seismic data were interpreted to obtain the attribute volumes that can reflect the characteristics of the fault fractured zones of the reservoirs.Then,the attribute volumes were proportionally fused with the initial low-frequency model and the spatial profile data of high-quality reservoirs obtained from the conventional inversion based on wave impedance.As a result,a new heterogeneous low-frequency model was formed.Using this model,multiple rounds of iterative inversions were conducted.The inversion results can truly describe the characteristics of the fault fractured zones in the heterogeneous reservoirs.The prediction results of 10 wells had coincidence rates of up to 92.86%.As indicated by the application,the method proposed in this study can improve the reservoir prediction performance and the prediction precision of fault-controlled reservoirs,thus effectively supporting the work in the study area.

Sedimentary copper deposits are the predominant type of copper (cobalt) mineralization in the Central African copper-cobalt metallogenic belt. To improve the prospecting efficiency of such deposits, the feasibility of applying the hydrocarbon-mercury gas measurement method in the prospecting of sedimentary copper deposits was studied in the Mabende-Likasi area of the Democratic Republic of Congo. As indicated by the test results, two known ore bodies show remarkable anomalies of multiple indicators of hydrocarbon and mercury, but the anomaly distribution is controlled by the occurrence of orebodies. Based on these findings, this study summarized the anomaly pattern of hydrocarbon-mercury gas and primarily explored the anomaly causes. Moreover, this study conducted the prospecting prediction of concealed copper (cobalt) deposits in the study area. An industrial copper orebody was discovered through drilling in the delineated favorable target area, thus achieving achieved prospecting results.

Focusing on the spring and lake water in the Hongshan Lake in the Tianshuihai area, Xinjiang, China, this study explored the formation process of the hydrochemical components in the water and the geochemical characteristics and sources of the water bodies through hydrogeochemical testing and analyses. Accordingly, the hydrocarbon-related hydrogeochemical information was obtained. The results are as follows: The spring water in the Hongshan Lake is weakly alkaline in general and dominated by brackish water. The mass concentration of main ions in the water bodies increases with increasing salinity. The water has a hydrochemical type of Na-HCO₃ and is mainly charged by atmospheric precipitation, which interacts with the surrounding rocks during the deep circulation along faults or fractures. The salinity, hydrochemical type, and characteristic coefficient of spring water indicate that the groundwater in this area features weak hydrodynamic force and deep metamorphic degree, which are similar to the characteristics of the formation water associated with hydrocarbon in oil fields. Therefore, it can be inferred that the geological environment in this area is conducive to the generation and preservation of hydrocarbon resources.

Based on the characteristics of the physical geography,topography,and hydroclimatology of Morocco and years of experience in the geochemical survey in Morocco, this study divided the geochemical landscapes in Morocco and plotted the geochemical landscape zoning map of Morocco. As a result, Morocco was divided into six first-order geochemical landscape areas, namely a forest coverage area, a semi-arid high mountain area, a humid-semi-humid middle-low mountain and hill area, an arid-semi-arid middle-low mountain and hill area, an arid desert and gobi area, and a desert coverage area. According to the elevation and surface cutting intensity, the humid-semi-humid and arid-semi-arid middle-low mountain and hill areas were subdivided into four second-level landscape areas each, namely a hill area, a low mountain area,a shallow-cutting middle mountain area,and a medium-deep-cutting middle-mountain area. Based on this division scheme, this study proposed several suggestions for geochemical surveys in Morocco.

The establishment of the Quaternary stratigraphic framework is of great significance for the study of regional stratigraphic correlation and paleogeographic environment evolution. The sedimentary strata since the Late Pleistocene have been extensively studied, but the research on the complete Quaternary stratigraphic framework is not yet sufficient. Therefore, paleomagnetic, AMS 14C, OSL, well logging, and lithostratigraphic studies were conducted on borehole QK4 (depth: 285.98 m) in the Lubei Plain. Based on the systematic paleomagnetic sampling (398 samples), processing, and testing, it is considered that the cores from borehole QK4 recorded Brunhes normal polarity chron, Maruyama reversed polarity chron, Gauss normal polarity chron, and some of their polarity subchrons. Based on the magnetic age framework, as well as MS 14C, OSL, well logging, and lithostratigraphic characteristics, the Quaternary strata revealed by borehole QK4 were divided, and it was determined that the bottom boundaries of the Holocene, Upper Pleistocene, Middle Pleistocene, and Lower Pleistocene strata have depths of 4.11 m, 23.49 m, 118.70 m, and 147.35 m, respectively. Moreover, as the strata revealed, the strata revealed by borehole QK4 include the Cenozoic Heituhu, Dazhan, Pingyuan, and Minghuazhen formations from top to bottom. The results allowed for the establishment of the Quaternary stratigraphic framework in the southern Lubei Plain, thus providing reliable petrological, chronological, and paleomagnetic evidence for the Quaternary stratigraphic division and correlation and palaeogeographic environmental evolution in the southern Lubei Plain.

To achieve the goals of peak carbon dioxide emissions and carbon neutrality, geothermal energy has great prospects for utilization as a type of widely distributed green and clean energy. The tectonic fissure-hosted geothermal water is regarded as an important type of hydrothermal energy for development and utilization because of its high water yield and easy reinjection. This study systematically analyzed the regional structures, formation lithology, water storage space, and water yield property of the urban area of Meixian County in the west of Guanzhong Plain through the regional integrated geophysical exploration, aiming to guide the target area prediction and well placement of geothermal wells. The results show that three concealed faults are present in the target area, of which two faults with favorable water yield property and large scale can be regarded as the faults of the target area. Based on this, geothermal wells were arranged near the fault prediction lines on the hanging wall of the faults, and the weathered zones of the bedrock surfaces were penetrated vertically along the dip angles of the faults. Given the actual geological conditions, such as the faults and the burial depth of the bedrock surface, the geothermal wells had an average drilling depth of 500 m from the bedrock surface. The drilling results show that there are dual-structure thermal reservoirs in the target area, including thermal reservoirs of pore water in the Neogene clastics and those of the bedrock fissure water. Among the eight geothermal wells, seven wells have a water yield of more than 100 m?/h, which mainly originates from the bedrock fissure water, and only one well has a relatively low water yield, which is mainly sourced from the pore water in the Neogene clastics.

Glacial landforms, such as cirques, razorback ridges, horn peaks, and alpine lakes, are commonly developed in the surrounding areas of the Tangbu section of Dongcuoqu in the Nujiang River Basin in southeastern Tibet, indicating that intensive glacial activities once occurred in this area. However, field surveys show that proluvium and alluvial-diluvial deposits are mainly distributed in the Quaternary surface of this section. The comprehensive analysis of the audio-frequency magnetotellurics and high-density measurement results of this area show that the electrical characteristics of the Quaternary in this section are highly consistent with the moraine deposit structure. Combined with the commonly developed glacial landforms in the surrounding area, it can be inferred that the Quaternary stratum in this section is mainly dominated by moraine deposits, which are covered with a layer of proluvium and alluvial-diluvial deposits. From the perspective of the electrical structure characteristics of the geophysical exploration results, the resistivity results of the audio-frequency magnetotellurics can effectively reflect the structural characteristics including the thickness of the moraine deposits, glacial valleys on the bedrock surface, and moraine lenses, and the resistivity results from high-density measurement can well reflect the characteristics of moraine melange, moraine lenses, and the long axis direction of large boulders.

Conventional methods for reservoir lithology identification suffer low precision and efficiency since reservoir lithologies have various types and complex compositions and alternate frequently.This study proposed a reservoir lithology identification method based on multi-scale time-frequency-space feature combination.Based on the original logging characteristics,this method introduced the multi-scale frequency-domain components from the complementary ensemble empirical mode decomposition (CEEMD) to improve the longitudinal resolution of log curves.Moreover,a multi-scale convolutional neural network-bidirectional gated recurrent unit-attention mechanism (CNN-BiGRU-AT) model was constructed to extract the spatio-temporal features of log data containing multi-scale frequency-domain components.In this way,the joint learning of time-frequency-space features of log data was realized.Finally,the model output was optimized using the attention mechanism to reduce the propagation of error information.To verify the reliability of this method,an experimental analysis was conducted using the data from five wells that have relatively complete data.As revealed by the analysis results,the identification accuracy of training and verification sets containing multi-scale frequency-domain components was increased by 9.50% and 8.66%,respectively in the comparative experiments of different data combinations.The method proposed in this study yielded sample identification accuracy of 94.11%.Compared with support vector machine (SVM),backpropagation (BP) neural network,convolutional neural network (CNN),bidirectional gated recurrent unit (BiGRU),and CNN-BiGRU fusion models, the identification accuracy of this method increased by 16.21%,14.54%,11.69%,5.05%,and 3.38%,respectively.

Poor illumination poses great challenges to the imaging of small-scale faults and pores.Subsurface attenuation leads to amplitude loss and phase distortion of seismic waves,and ignoring such attenuation during imaging will blur migration amplitudes.The Q-compensated least-squares reverse time migration (QLSRTM) can improve the imaging of these small-scale structures,but it requires a huge amount of iterations and computational cost.To improve the imaging effect of these small-scale structures,this study proposed a geological-target-oriented joint QLSRTM (J-QLSRTM) that fully utilizes diffracted waves.In this method,a new objective function and gradient formula was constructed.Moreover,the Q-compensated wavefield propagation operators,Q-compensated adjoint operators,and Q-attenuated demigration operators were derived for both primary and diffracted waves based on the inversion and adjoint theories.The numerical examples verified that the proposed J-QLSRTM is superior to the conventional QLSRTM and the acoustic J-LSRTM.

Southern Sichuan Province has widely developed karsts and densely distributed coal mine goafs, which cannot be accurately detected and identified using a single existent exploration method. Consequently, large-scale and industrial drilling for shale gas is prone to induce failures and complex events. In light of the complex topographic and geological conditions in southern Sichuan, this study conducted tests and comparative analysis using multiple engineering geophysical exploration methods including electrical resistivity imaging, shallow seismic method, transient electromagnetic method, audio-magnetotelluric method, and microtremor survey method. As a result, an integrated engineering geophysical exploration technology for shale gas well platforms in southern Sichuan was formed and applied to the construction of shale gas well platforms. As indicated by drilling results, the integrated technology can effectively identify unfavorable geological bodies (e.g., shallow karsts, coal mine goafs, and overburdens) at a depth of less than 1000 m and provide technical support for siting shale gas well platforms, optimizing casing programs, predicting drilling risks, shortening drilling cycles, and protecting ecological environment, with remarkable economic, social, and ecological benefits having been achieved. Moreover, this integrated technology provides a technical guarantee for the construction of both the Changning-Weiyuan national shale gas demonstration zone and the southern Sichuan shale gas exploration and development pilot zone and accelerates the shale gas development in southern Sichuan.

Carbonate reservoirs have various pores and complex pore structures.However,the microstructure of rocks cannot be characterized using conventional saturation evaluation models,making it extremely difficult to perform the saturation evaluation of carbonate reservoirs.Given this,this study proposed a Thomeer saturation model combined with the nuclear magnetic resonance (NMR) logging based on the data of capillary pressure curves and NMR logging.Specifically,information about the structure of the pore system in the mercury injection data was analyzed,and then the capillary pressure curves of multiple pore types were obtained through fitting using the Thomeer function.Finally,the complex pore structure was characterized using multiple Thomeer curves.The NMR logging is the only logging method that can continuously and quantitatively characterize the pore structure of reservoirs.The Thomeer parameters B_v,P_d,and G and the modal element Porositon of the maximum pore throat diameter were calculated using the logarithmic mean of T2 transverse relaxation time for NMR (T2LM) and the NMR total porosity (MPHS),as well as the classification of pore throat R35.Accordingly,the saturation evaluation model for carbonates reservoirs with complex pore structures was constructed.This model allows for the continuous evaluation of formation pore structure that cannot be achieved using experimental methods.This model was applied to the saturation evaluation of the carbonate reservoirs with complex pore structures in oilfield X in the Middle East.By comparison with the J function model and Archie's formula,this model decreased the relative error from 0.496 and 0.442,respectively to 0.272,better characterized the variation trend,and achieved encouraging application effects regardless of the saturation of reservoirs.Therefore,this model can minimize the impacts of carbonate reservoirs with complex pore structures and improve the precision of the reservoir saturation evaluation.

This study aims to explore the current field distribution characteristics and detection influencing factors of the focusing DC induced polarization (IP) method for tunnels. The study processes are as follows: the normal and anomalous potentials of the spatial electric field were calculated using the finite element method; a homogeneous 3D geoelectric detection model was constructed using the Comsol software, the model was divided into grid cells using the adaptive algorithm for tetrahedral mesh generation, and the numerical calculation precision was compared and analyzed; the distribution and change patterns of the focusing current field were investigated, and the range of the current ratio of the focusing effect was determined, and a 3D geoelectric model was constructed for anomalous geological structures in front of the tunneling section, and the influences of factors such as the area of the tunneling section, interference bodies, and current ratio coefficient of focusing effect on the IP effect parameters were simulated through the forward modeling using the equivalent resistivity method. The results are as follows: the focusing DC IP method was highly sensitive to the detection of the unfavorable geological bodies in front of the tunneling section; the impact of the interference bodies in the tunnel cavity on the detection of the anomalous target bodies can be ignored; the farther the lateral anomalous interference bodies from the tunnel floor, the less the impact on the detection of the anomalous target bodies, and the exploration distance can be effectively increased by increasing the area of the tunneling section and the current ratio coefficient of the focusing effect. This study can be utilized as a basis and reference for the inversion using the focusing DC IP method and is greatly significant for promoting the development of the focusing electrical exploration theory.

The precision evaluation of an aeromagnetic survey system is an important part of a magnetic survey. This study obtained airborne and ground magnetic data through flight experiments in a certain survey area of Inner Mongolia. Then, the high-precision ground magnetic survey data was upward-continued to the height of the flight course using the interpolation-iteration and equivalent source methods. Finally, the external coincidence precision of the aeromagnetic survey system was evaluated by comparison with the aeromagnetic survey data. The precision evaluation results of the two continuation methods are better than 5 nT, reflecting the actual precision level of the aeromagnetic survey system. Therefore, the research methods in this study can provide references for the evaluation of the external coincidence precision of an aeromagnetic survey system and can also be used for online calibration of the scale factor, deviation, and other parameters of newly developed aerial magnetometers.

The phase difference (i.e., time difference) and amplitude difference between the geomagnetic data of the offshore work area and the geomagnetic diurnal variation data of the remote stations are still challenges to the precision of the marine magnetic survey network. Based on the stations on both sides of the East China Sea and three stations in Europe at higher latitudes, this study analyzed and made statistics on the numerical differences in morphological characteristics, phase differences, and amplitude differences of the diurnal variation curves during the daytime, nighttime, and the periods of intense magnetic disturbance. The results are as follows. During the daytime, the phase difference between the stations is constantly changing, resulting in a large amplitude difference around noon. During the nighttime, the data of the stations have consistent phases, and the amplitude difference is mostly less than 4 nT. During strong magnetic disturbance activities such as magnetic storms, the phases of the stations are consistent, and the amplitude difference is even smaller than that during quiet days. According to the survey data of the ocean, the absolute value of the difference at intersections between the survey lines during magnetic storms and quiet days is less than 3.2 nT. The variation characteristics of the phase difference and amplitude difference of the geomagnetic diurnal data between stations facilitate the diurnal variation correction of the marine geomagnetic data.

This study designed a group of 2D peak-valley comprehensive terrain models with different widths and slopes and investigated the influence of differently undulating terrains in mountainous areas on the audiomagnetotelluric (AMT) data and corresponding distortion characteristics from seven aspects, namely polarization modes, frequency, positions of measurement points, the width of a mountain top, the elevation difference and slope of terrain, and phase curves. The results are as follows. The transverse magnetic mode (TM mode) is more susceptible to terrain than the transverse electric mode (TE mode). The undulating terrain has little influence on the high-frequency parts of AMT data but has a great influence on their low-frequency parts. The apparent resistivity and phase of different frequency points at a measurement point reflect the comprehensive influence of all terrains within the skin depth level rather than just the influence of a single mountain peak or valley near the measurement point. Measurement points located at the mountain peaks are more easily affected by terrains than those in the valleys. Moreover, narrower mountain tops correspond to greater elevation differences of terrain, and steeper terrain exerts greater influence. In addition, the comparison of the 2D_TE results of the inversion considering and not considering terrains show that the 2D inversion considering terrains can effectively eliminate the influence of terrain. The 2D inversion considering terrains was carried out for measured AMT data. As indicated by the inversion results, the 2D inversion considering terrains can effectively eliminate the false high and low resistance anomalies and relieve the "hanging surface" phenomenon of signals, and the results corresponded well with the horizons with encountered manganese of three boreholes.

In the compensation of the aeromagnetic gradient tensor data based on superconducting, the simulation results of the compensation model often differ from the compensation results of the survey data. To establish a model that is valid for measured data, this study analyzed the sources of errors, proposed a comprehensive compensation model by combining magnetic interference, installation errors, and the degree of unbalance, and determined the method to solve the model. Moreover, this study compensated the measured data using the comprehensive compensation model proposed and verified the compensation effects. The experimental results show that the comprehensive compensation model is applicable to the compensation of measured data since it can not only effectively reduce the influence of external interference but also can improve the quality of magnetic gradient tensor data and achieve significant compensation effects.

Upward continuation is one of the important methods used to separate gravity anomalies. However, how to quantitatively select an appropriate upward-continuation height has always been a problem in the application of this method. Given this, this paper proposes a curvature analysis method based on the least square method to quantitatively determine a reasonable upward-continuation height. The steps of this method are as follows. Perform upward continuation to different adjacent heights for observation data, and then use the least square method to estimate the least square error of the upward continued value of adjacent heights.There is a maximum curvature in the least square curve of upward-continued values of all adjacent heights.At the point of the maximum curvature, the local anomalies are attenuated to the greatest extent, while the regional anomalies are preserved as far as possible. Therefore, this point can be approximately regarded as the optimal upward-continuation height. As indicated by tests using the data of a theoretical model, the method proposed in this paper can be used to qualitatively determine a suitable upward-continuation height, thus providing an important reference for the selection of upward-continuation height in practical applications.

The MTU series magnetotelluric sounders produced by Phoenix Geophysics Ltd. in Canada have been widely used in various fields of earth exploration because of their advantages, such as small weight and stable and reliable data acquisition. However, their special data formats make the data processing troublesome. At present, most of the data processing depends on the SSMT-2000 software developed by Phoenix Geophysics, which is not conducive to the improvement and application of data processing methods. By studying the formats of data files of MTU series magnetotelluric sounders, this study used the UltraEdit software to analyze the structure and rules of the data files and analyzed and studied TBL, CLB, CLC, and TS files based on the C# programming language. As a result, this study transcoded the data files from indigestible binary files into plain files that are easy to understand and provided the modification and editing module of TBL parameter files, the data analysis module of CLC and CLB files, and the transformation module of TS files. The data measured in the field were edited using the program developed in this study. The test results verify that the program can modify TBL file parameters, analyze CLB and CLC files, and convert TS files. Therefore, this study provides a new idea and method for studying such binary files.

There is a lack of selection bases in the geochemical anomaly identification and the reconstruction of the geochemical background conforming to the metallogenic distribution using deep learning algorithms with different network structures. Given this, based on the 1∶200 000 stream sediment data of the copper-zinc-silver metallogenic area in southwestern Fujian Province, this study extracted the combined structural characteristics, spatial distribution characteristics, and mixed characteristics of multiple elements in the samples using three unsupervised deep learning models, i.e., AE, MCAE, and FCAE. Then, these characteristics were used to reconstruct the geochemical background and simulate the metallogenic distribution. The results show that the anomaly areas delineated by the FCAE model were the most consistent with the known copper ore occurrences, followed by the MCAE and AE models. The FCAE, MCAE, and AE models had an area under the curve (AUC) score of 0.80, 0.78, and 0.61, respectively. Moreover, the FCAE and AE models were not sensitive to the change in the convolution window size. These results indicate that when deep learning algorithms are constructed for geochemical anomaly identification, the algorithms based on the extraction of spatial distribution characteristics or mixed characteristics perform well, and those based on the extraction of combined structural characteristics or mixed characteristics have a strong anti-interference ability for the noise caused by the change or inconsistency of the spatial observation scale. This study provides some effective selection bases for constructing geochemical anomaly identification models based on deep learning algorithms.

The deep strata in the Ledong area of the Yinggehai Basin have a complex pressure structure.As indicated by the surveyed pressure data,strata at different depths and horizons have greatly different pore pressure.Especially in the Huangliu Formation,the pore pressure shows a large transverse span.Moreover,it tends to reduce at the top but rises rapidly at the bottom,with a pressure coefficient of up to 2.3,indicating the presence of significant pressure mutation.Pressure prediction using only the undercompaction model yields large errors and thus is prone to induce engineering accidents.To effectively predict the formation pressure,it is necessary to determine the genetic mechanisms of overpressure.This study effectively identified the genetic mechanisms of the overpressure using the cross plots of vertical effective stress vs logging response.The identification results show that the genetic mechanisms of the deep overpressure in the Ledong area mainly include mechanical unbalanced compaction,chemical compaction,vertical pressure transmission along faults,and hydrocarbon-generating pressurization.A proper pressure prediction method was established based on the defined genetic mechanisms,thus improving the prediction precision and ensuring the smooth construction of drilling engineering.

Owing to the limitations of both the field environment for seismic data acquisition and the performance of instruments,the seismic signals collected in seismic exploration are inevitably mixed with strong noise,thus greatly affecting the subsequent processing and interpretation.In recent years,multi-scale geometric analysis methods have become an important topic in noise suppression owing to their unique advantages.This study proposed suppressing the seismic noise using a non-local mean (NLM) algorithm in the Shearlet domain.First,the non-subsampled Shearlet transform (NSST) was performed for seismic signals.Then,the decomposed coefficient subset was further processed using the NLM method,and the weight function was improved by using eight Sobel operators to approximate the omnidirectional structure.Finally,the inverse Shearlet transform was performed for the coefficients to obtain the denoised seismic signals.Experimental results show that this combined algorithm can effectively suppress the random noise and preserve the weak events,thus showing high practicability in the seismic data processing.

Multiple suppression is the key to marine seismic data processing.Efficient and accurate identification and suppression of multiples while protecting primary reflected waves is the focus of seismic data processing.This study carried out the multiple suppression in the S-transform domain using the CMP stacking based on the similarity of seismic signals between the common midpoint (CMP) gather and the stack trace.First,the initial multiple subtraction was completed through the normal moveout (NMO) correction of multiple velocity and subtracting the stack trace data from the CMP gather data.As a result,the residual multiples in the wave field exist in the form of random noise.Then,the NMO correction was conducted for the velocity of primary reflected waves of the seismic wave field, for which multiples were subtracted.Afterward,the similarity filtering was conducted for the S-transform spectra of the CMP gather,with the stack trace of the primary reflected wave velocity as the initial model.In this way,the residual multiples were eliminated.The validity tests based on both the theoretical data and the actual data show that the method proposed in this study can efficiently suppress multiples and improve the imaging precision of reflected waves.

Soil monitoring is of significance for guiding the determination of the ecological quality of soil, the active ecological restoration and prevention of soil pollution, and the sustainable monitoring and utilization of land resources. To investigate the temporal and spatial changes in the soil monitoring indices in Yixing City, Jiangsu Province, this study collected the geochemical data on 426 soil samples taken during the multi-purpose geochemical survey of Yixing City in 2004 and 4 458 soil samples taken during the 1∶50 000 land quality geochemical survey in 2015. Based on these data, this study analyzed the changes in important soil environmental parameters of the study area using the geographic information system (GIS) and statistics. Moreover, it determined the changes in the parameters or element concentrations using box-whisker plots and t-tests, conducted an error analysis using the nugget value (C₀) based on the semivariance function, and evaluated and analyzed different spatial variables. The results are as follows. From 2004 to 2015, the organic matter (OM) and nutrient elements such as nitrogen, phosphorus, and boron showed an upward trend; the pH of soil showed a significant downward trend; the contents of selenium and heavy metals such as cadmium, copper, lead, and zinc showed an upward trend, and the arsenic content did not change significantly.

Based on the statistical analysis of the Se distribution in 8,835 soil samples and 240 sets of crop-root soil samples, as well as related survey data in the Shizuishan area of Ningxia, this study summarized the element geochemical characteristics of the local Se-rich soil and explored the development and utilization prospects of the soil and related issues. The study results are as follows. ① The newly delineated Se-rich land (soil with Se content of ≥0.222×10^-6; local standard of Ningxia) covers a total area of more than 1,000 km², including more than 25% of Se-rich farmland, and the effective Se content is mostly over 10% of Se in the soil; ② The Se-rich soil has pH of greater than 7.5 and organic matter content of less than 10.26%, without heavy metal pollution. There are significant positive correlations between the Se content and the contents of organic matter, B, Mn, Mo, Cu, and Zn and a negative correlation between the Se content and pH; ③ The correlation coefficient between effective Se and Se in the soil is r = 0.39, and those between effective Se and OM, CEC, and N are 0.33 to 0.5; ④ Among the 10 types of Se-rich agricultural products (i.e., Se-rich wheat) obtained in Se-enrich soil through spot check, the wheat has been proven to have the strongest capacity to absorb Se, with an average bioconcentration coefficient of 0.12; ⑤ Since the unique Se-rich soil resources in this area is of great value in development and utilization, it is necessary to strengthen the R&D of characteristic Se-rich crops (i.e., wheat, rice, wolfberry, and grape) and the development of relevant Se-rich standards through scientific research and reasonable planning.

Bioavailable selenium (Se) is an important indicator used to evaluate the supply capacity of Se in the soil to plants. There is a lack of national standard methods for testing bioavailable Se in the soil in China presently. This study used ten different chemical extractants to extract bioavailable Se from the soil. The results show that the extraction capacity of extractants was in the order of NaOH (10.57%) > SOL-Se+EX-Se (8.10%) > AB-DTPA (6.79) > NaHCO₃ (4.99%) > K₂SO₄ (4.57%) > KH₂PO₄-K₂HPO₄ (4.33%) > KH₂PO₄ (3.05%) > SOL-Se (2.28%) > EDTA (1.40%) > NH₄F-HCl (1.22%). Among them, the bioavailable Se extracted from the soil by KH₂PO₄, NaHCO₃, SOL-Se, KH₂PO₄-K₂HPO₄, and AB-DTPA was significantly correlated with the Se content of crops. As revealed by the relationship between the percentage content of bioavailable Se in soil and soil properties, the percentage content of bioavailable Se in soil significantly correlated with indicators such as the chemical index of alteration (CIA), LOI, pH, Eh, P, and SiO₂. Among them, pH and Eh mainly affect the existence form of Se in the soil, while indicators such as CIA, LOI, P, and SiO₂ reflect the alteration degree of soil and the effect of adsorbates on bioavailable Se in soil. The results of this study can provide data support and a scientific basis for the development of Se-based ecological agriculture and the development and utilization of Se-rich land resources.

Based on the evaluation data of agricultural geological surveys in Minhou County, Fujian Province, this study investigated the distribution of selenium contents in the surface soil of the cultivated land and garden plots in Minhou County and its major controlling factors. Moreover, it analyzed the selenium contents in agricultural products. The results are as follows. The selenium content in the surface soil is controlled by the geological setting. The areas with Late Jurassic concealed granite porphyries occurring have significantly higher soil selenium content than other areas. Moreover, different landforms, soil types, and land uses have certain effects on selenium content in the soil. Most of the agricultural products in the study area have low selenium content. The main selenium-rich crop is rice, which has a selenium accumulation rate of 78.6% according to the preliminary evaluation. However, some rice samples had excessive As or Cd content. Therefore, attention should be paid to the risk of excessive heavy metals in the development and utilization of selenium-rich rice. Based on the distribution of clean selenium-rich soil and the selenium-rich characteristics of agricultural products, this study determined nine potential areas of natural selenium-rich land in the study area.

To quickly and effectively detect the hidden hazards of dams,this study proposed the microtremor B-mode ultrasound technology based on linear arrays.Most of the (earth) dams also act as highways,and the vibration signals generated from running vehicles propagate along dams.Therefore,this study proposed deploying linear arrays along the dams,with the vibration propagation direction consistent with the signal receiving direction.In this way,abundant vibration sources can be provided for detecting hidden hazards of the dams.The results of this study show that the data on multiple exploration points can be simultaneously acquired using the multi-channel acquisition technique based on linear arrays,thus improving the efficiency of field data acquisition.Moreover,the influence of source differences can be avoided,and the lateral resolution and the accuracy of exploration results can be improved.The technology proposed in this study was applied to the pre-flood safety inspection of a dam in Jiujiang,Jiangxi Province.Three low-velocity hidden hazards were identified in this dam and were presumed to be the weak layers of the dam foundation and the loose media of the dam body.Practices have proved that this technology effectively counteracts the deficiencies (i.e.,low efficiency and lateral resolution) of the previous microtremor exploration.Moreover,this technology allows scanning at a spacing of 1 m or 0.5 m,thus improving the lateral resolution.This study will provide efficient and accurate guidance for dam safety management.

As a fast and nondestructive geophysical exploration technique,the natural source surface wave technique performs well in exploration in a complex urban environment by extracting surface waves and other information using the natural earth vibration.This study applied this technique in an urban planning area to ascertain the distribution characteristics of the strata in the area through section interpretation,the extraction of site evaluation parameters including equivalent shear wave velocity and predominant period,and 3D visualized plotting.It can be concluded that the planning area has no concealed fault and thus has excellent site conditions.The results of this study can be utilized as an important reference for the site evaluation of similar areas.

To explore in detail superficial paleochannels in Xiong'an New Area,this study investigated two profiles in the study area using the high-density resistivity method based on previous remote sensing.The interpretation results were verified through drilling.The distribution range of the paleochannels that was delineated using the high-density resistivity method was more accurate than that obtained from remote sensing.This study determined that the superficial paleochannels in the study area exhibit curved,tortuous,and braided planar distribution,achieving excellent application performance in the detailed exploration of superficial paleochannels.This study provided a new idea for future exploration and study of superficial paleochannels and can be used as a reference for the selection of methods used to investigate paleochannels in similar geological conditions.