Syngeneic and epigenetic components in soil or regolith were discussed from definition. Epigenetic anomalies were classified as lateral and top anomalies,and top epigenetic anomalies are the base for deep penetration technology design. The principle of deep penetrating geochemical exploration technology is to extract the epigenetic components related to deep mineralization without destroying or less destroying the soil matrix (syngeneic components). The authors use a case study to illustrate what the epigenetic anomalies are and why conventional geochemical exploration (total) cannot be used for mineral exploration in overburden areas. From the perspective of extracting epigenetic anomalies in soil, the history, updates and problems of various deep penetration technologies are analyzed.

In order to solve the problem of deep prospecting in the Yuershanore ore block and its peripheral Hongyanxi-Ma'erqiaooreblock in the Woxi mining area, the authors carried out the tests of structural superimposition halo and hydrocarbon mercury comprehensive gas measurement in this area. Based on the study of the evolution law of hydrocarbon and mercury components in different geological bodies and different elevations and the characteristics of geochemical hydrocarbon and mercury anomalies formed in the upper soil of the orebody, the authors summarized the structure and superposition characteristics of soil geochemical anomaly field as well as the corresponding relationship with space so as to carry out the deep prospecting prediction. In addition, the test of the hydrocarbon and mercury superposition halo was carried out in the Hongyanxi-Ma'erqiao prediction areain the periphery. Based on the comprehensive study of prospecting methods, it is found that there are two different types of superposition fields in the soil geochemical field of Hongyanxi-Maherqiao ore block: one is deep source superposition field, where the correlation between Au and hydrocarbon components is good, the hydrocarbon anomaly components are complete, the Au and Hg anomalies are good, with deep source ore-forming hydrothermal superposition, and the deep prospecting potential is great; the other is syngenetic superposition field, where the correlation between Au and hydrocarbon components is poor, the element combination is relatively simple, and there is no hydrocarbon component anomaly, exhibiting little significance for ore prospecting.The hydrocarbon anomaly mode is dominated by dual bimodal anomaly mode, and there is a good hydrocarbon mercury comprehensive superposition anomaly in the low value area between the two peaks of hydrocarbon anomaly, indicating that there is a parallel blind vein in the depth. Drilling verification shows that the deep source superposition field has a gold orebody with a real thickness of 8.58 m and an average grade of 3.55×10^-6 gold, while the syngenetic superposition field only has gold mineralization. Good prediction results have been achieved.

A lead-zinc deposit in Hebei Province is the only medium-sized porphyry lead-zinc deposit in Yanshan area, Many years' geological exploration work after its discovery has not made major prospecting breakthrough.After comprehensive research on geophysical and geochemical exploration and geological data obtained over the years in combination with a series of work such as high-power IP area measurement,it is believed that the anomalous elements of geochemical exploration in this area are obviously in zoning form, the anomaly of the electrical shock is obvious, the metallogenic series is complete, and the prospecting potential is large.Through drilling verification, thick high-grade lead-zinc deposits were found in the periphery of the porphyry and in the contact zone,copper and molybdenum deposits were found in the depth, which form a complete metallogenic series of porphyry deposits. Therefore, a new breakthrough in prospecting in this area has been realized. This area has a potential to become a large lead-zinc deposit, thus further expanding the resource prospect of the region.

A procedure to screen the elements used in the research on the elemental zonation in a primary halo is rarely conducted, which is not conducive to the acquisition of an accurate understanding of the rules of elemental zonation. In this paper, the authors chose the Zhajiatongna gold deposit in Qinghai Province as a study case and aimed to study the difference between ore-forming metallic elements in the ability of forming a primary halo through comparing the elemental enrichment degrees in the wall rocks, mineralized wall rocks, and orebodies and on the basis of 2 779 samples from the drill cores of the deposit. It is found that the concentrations of Au, As, Sb, Hg, W, and Ag progressively increase from the wall rocks through mineralized wall rocks to orebodies, indicating a greater possibility of forming a primary halo for these elements. Zinc is enriched only in the orebodies, with less possibility of forming a large-scale primary halo. Elements of Mo, Cu, Pb, and Sn show insignificant enrichment or even show depletion, indicating a less possibility of forming a primary halo.A trend of enrichment zonation of ore-forming elements was recognized: Au, As, Sb in the wall rocks, Au, As, Sb, W, Hg (Ag) in the mineralized wall rocks, and Au, As, Ag, Sb, W, Hg and Zn in the orebodies. Elements show a decreasing weight of enrichment in the mineralized wall rocks in order of As, Hg, Au, Sb, W, Mo, Sn, Pb, Zn, Cu, and Ag, suggesting the progressively decreasing ability of entering into the wall rocks from the orebodies in order of low-temperature metallogenic elements through medium-temperature metallogenic elements to high-temperature metallogenic elements. Therefore, in the Zhajiatongna gold deposit, elements such as As, Hg, Au, Sb and W are optimal for researches on elemental zonation and mineral prediction.

Rich iron ore has been drilled in the depth from 748 m to 1 542 m in Qihe-Yucheng area. As the Quaternary sediments cover more than 500 m in thickness, the geophysical field information of the rich iron ore is weak and hence the prospecting is difficult. By studying airborne and ground gravity and magnetic anomaly characteristics of mineralization anomaly and using methods such as reduction to the pole, vertical derivative and total gradient module, the authors further reduced the prospecting target and provided a basis for the drilling work. The authors extracted the direct prospecting information of rich iron ore, established the geophysical prospecting signs of this area and delineated 7 key exploration areas. The results of this research provide an important basis for the subsequent deployment of prospecting work in Qihe-Yucheng area.

Three-dimensional geological modeling is an important way to realize the background of deep mineral exploration. Based on three-dimensional modeling of ore-controlling geological bodies, this method can directly describe the spatial, genetic and evolutionary relationship between the ore controlling factors. At present, the 3D modeling mainly uses geological data, but in the absence of drilling and other known information, it is difficult to construct a reliable 3D geological model. In order to overcome the disadvantages of poor accuracy and low reliability of conventional 3D geological modeling, the authors put forward an effective method based on the prior information. In this approach, a series of sections obtained by the 2.5D interactive inversion and electrical inversion, combined with the sections of 3D physical property inversion, are employed to correct the process of building a 3D geological model. With this method, the 3D geological model of the dome structure in Pengshan area has been successfully established. On this basis, the cause of the formation of the Pengshan dome structure is discussed.

In exploration of the sandstone type uranium deposits, the effective information of gamma ray spectrum is often covered by surface information due to the influence of surface overburden and other factors. In order to extract information related to uranium mineralization, the authors carried out the application of thorium normalization by gamma ray spectrum in Dalin area. The residual anomaly of uranium extracted is in agreement with the distribution of the known uranium orebodies and faults. The analytical results show that the method of thorium normalization can exhibit the distribution of faults effectively. Within this area uranium mineralization is controlled by faults, the abnormal area of uranium residual is also the transition zone of oxidation-reduction, which provides the basis for the next exploration within this area.

The Fuxingtun silver-lead-zinc polymetallic deposit is the first large-scale silver-lead-zinc polymetallic deposit discovered in the Mesozoic continental volcanic basin in the Daxinganling metallogenic belt in the past two years. During the census of the deposit, geophysical methods such as high-precision magnetic survey on the ground, time-domain induced polarization method, and AMT sounding method were conducted. Geophysical methods played an important guiding role in the exploration of Fuxingtun silver-lead-zinc polymetallic deposit. ① Through the processing and interpretation of ground magnetic anomaly data (using RGIS software),the structure of the census area were determined; ② Using the characteristics of geomagnetic anomaly and apparent resistivity anomaly, combined with the exposed lithology on the surface, the caldera rifted basin was determined;③ Using the electrical sounding data, the formation process and structural characteristics of the faulted basin was determined, as well as the multi-stage of fault structure and the multi-stage of sulfide precipitation; ④ Based on the abnormal characteristics of apparent polarizability and the geological structure environment, the nature of the field source and the source of mineralization materials were determined;⑤ The intrusive body of cylindrical subvolcanic rock was delineated by AMT sounding data. Based on the above research results and drilling data, this paper studies the formation mechanism of the deposit and summarizes a set of application ideas for geophysical methods to find such deposits.

As one of the large tin-polymetallic deposits in the world, the Dachang deposit has complicated metallogenic mechanism and rich hidden mineral resources. In order to detect the distribution and study mineralization mechanism of the concealed deposits around the cage and cover rock in the Dachang ore district, the authors finely processed the audio magnetoelectromagnetic data covering the Dachang ore district, and obtained a two-dimensional electrical structure model within the depth of 3 km. According to the results of resistivity model, the location of concealed granite and orebody was determined. Granite is characterized by high resistance and is buried at a depth of about 1.5 km, with the formation of ridge uplift along the fault structure. The low-resistivity orebody is located in the middle Devonian strata at the top of granite, so it is inferred that the orebody was developed from the granite at the bottom, which indicates that granite has an obvious ore-controlling effect. According to the zonal characteristics of copper in the near place and tin in the distant place as well as anomalies of metallic elements in the Dachang ore district, it is most possible to find skarn type Zn-Cu deposits and Sb-W deposits. The research shows that, in the late Cretaceous period, the magmatic hydrothermal fluids of the middle and lower crust together with a small amount of upper mantle rose to the shallow Devonian strata of the crust along the basement fault in the NW direction, and then formed mineralization with surrounding rocks through crystallization differentiation.

Urban active fault detection plays an important role in the process of urban development and construction and also in ensuring the safety of people's lives and property.In this paper,with the purpose of identifying the activity of Luocheng fault and Shangtianqiao-Simen fault and on the basis of geometry,kinematics and chronology of the fault determined by the seismic geological survey,the authors detected the specific location of the fault that lies at the most likely active segment and is covered by the Quaternary sediments by high-density electrical method and seismic imaging method,which was then verified by drilling arrangement.In addition,the latest active age of the fault was determined through the offset relationship between the fault and the Quaternary overburden.The results show that the location of Luocheng fault and Shangtianqiao-Simen fault in the concealed segment can be accurately detected by the high-density electrical methods and seismic mapping method,and the fault activity age is determined to be the early Pleistocene based on the fact that fracture surface,scratch,cataclasite and structural brecciaa are developed,but the fault does not cut the Quaternary overburden.According to the requirements of relevant specifications,Luocheng fault and Shangtianqiao-Simen fault have not been active since the late Pleistocene,so the construction planning of Luocheng county does not need to take avoidance measures,and the appraisal results provide safety guarantee for the project construction of Luocheng County in the future.

Through the improvement of CH-3 UAV aeromagnetic survey system of measurement and control software and hardware, differential GPS positioning data synchronization, system adaptability modification, and horizontal transverse gradient measurement, the authors carried out 1∶25 000 large scale aeromagnetic survey test in Rudong coastal tidal flats area in Jiangsu Province, and verified the high precision measurement and control so as to improve the system stability and other key performance. Good application results were achieved in concealed rock mass, and fault structure and magnetic interface distribution were inferred, which shows that the method has broad application prospects in providing effective basic geological and engineering geological information for the development and utilization of the beach area.

The shallow resources of lead-zinc deposits are gradually decreasing in eastern Bangpu of Tibet, and hence deep and side exploration is imperative. The authors used CSAMT to carry out deep exploration and make prospecting prediction of lead-zinc deposits in the Bangpu-Digei mining area. The geophysical profiles were deployed in accordance with the 100 m×40 m survey network, and 373 physical points were determined. CSAMT data processing was conducted for the magnetic field intensity so as to calculate the full-region apparent resistivity and obtain the full-region apparent resistivity data at 42 840 sites. Then, the CSAMT anomaly map of full-region apparent resistivity in the exploration area were compiled, and four abnormal areas of electrical conductivity were delineated, i.e., high resistivity abnormal areas R1, R2, R3 and low resistivity abnormal areas R4. Combined with previous exploration data, the authors carried out geological interpretation of CSAMT data and established corresponding prospecting prediction model. The further drilling verification results prove the reliability of CSAMT prediction results.

Based on the latest 1∶250 000 gravity data of Delingha area and combined with the relevant known data, the authors carried out the new extraction and inversion interpretation of gravity anomaly. The study shows that the current gravity anomaly characteristics in Delingha area can reflect the basement structure. In this paper, 14 regional fault structures were interpreted by wavelet fault analysis method, and the basement structure of "five depressions and three uplifts" in Delingha area was recognized by the density interface inversion calculation of Parker method. The uplift and depression pattern of the current regional basement in Delingha area was defined, the undulating change and depth of the uplift and depression of the basement were inferred, and the attribution and supplement of some previous achievements were made. The authors hope that the result of this study will play a guiding role in the deep structural analysis, mineralization research and oil and gas resource prediction in Delingha area, especially in the Chaidong basin.

M02 member of Upper Dual Formation of Lower Cretaceous in B Oilfield in Kazakhstan belongs to braided fluvial deposits.The reservoirs are mainly gravel-bearing sandstone and fine sandstone.Sand bodies change rapidly in both vertical and horizontal directions.Uncertainty of reservoir distribution laws seriously restricts the progressive exploration and development process of the oilfield.Based on a new round of fine structure interpretation,the comprehensive application of a series of reservoir prediction techniques such as fine synthetic seismogram calibration,seismic forward modeling,seismic attribute analysis,conventional seismic inversion and geostatistical inversion was successfully implemented,which eliminated the multi-solution of seismic attribute analysis,made clear sand reservoir macroscopic distribution laws,and finely depicted the distribution characteristics of thin sand bodies in M02 breaking through the limitation of conventional seismic resolution.Finally,a comprehensive technological sequence of seismic reservoir prediction techniques suitable for this oilfield was established.Successful application of this technology sequence in this region provides a powerful basis for rolling evaluation and water injection development and has made a great contribution to increasing reserves and production of the oilfield.Meanwhile,it has reference and guidance significance for reservoir prediction in similar blocks.

In thin overburden area,the application of shallow P-wave reflection to fault detection can only obtain the reflected waves of the bedrock top surface,but it is difficult to accurately determine the location and buried depth of the fault.In this paper,the authors first applied shallow P-wave reflection method to obtain the approximate location and buried depth of the fault,then used ultra-shallow S-wave reflection method to confirm the location and supplement the shallow fault information.Through the joint detection, more reliable localization of the fault plane position was achieved,and more abundant structural feature information of faults ranging from shallow to ultra-shallow depths was obtained.On the basis of joint detection,the drilling exploration composite geological section was arranged to verify the existence of the fault.The results show that the P-wave and S-wave joint detection of buried faults in thin overburden area is more effective than a single method.It can obtain more fault information and can provide a more reliable basis for the layout of drill exploration composite geological section.

This paper briefly reviews the history and the overall work deployment of the U.S. National Uranium Resource Evaluation (NURE) program, with emphasis placed on the key techniques of airborne exploration. The airborne exploration included airborne gamma-ray spectrometry (AGRS) and aeromagnetic survey, which collected radiometric and magnetic data over the conterminous United States and Alaska. The airborne program systematically covered each 1° by 2° national topographic map series (NTMS) quadrangles, which were used to locate potential radioactive mineral deposits. The program played an important role in uranium resource and environmental radiation level evaluation, which has far-reaching definition and meaning. The experience and practices of the program should be used for reference. According to the current status of China's survey, top-level design for AGRS should be strengthened. This paper also proposes a national program of AGRS surveys for achieving coverage of terrestrial radioactivity and building a measurement and monitoring system with Chinese characteristics.

Affected by the complex surface geological conditions,the degree of geological survey in coastal tidal-flat areas is quite low,which limits the development level of relevant geological survey methods.Shallow seismic exploration technology plays an important role in the geological survey of coastal shoals.However,seismic data acquisition in this area is restricted by the applicability of exploration equipment,especially the source.In order to meet the detection requirement in coastal tidal flats and consider the complex near surface conditions,the authors carried out an experimental study of applicability analysis of shallow seismic sources,which also took the resolution,SNR and work efficiency into consideration.Light and flexible sources were selected in this paper,orderly including the tamping source,hammering source,drop-hammer source and sparker source.A comparison between different sources shows that spark source gets the best performance in such aspects as reflection wave frequency,frequency band,continuity in seismic events,detecting depth,SNR and noise resistance,which can also improve the acquisition efficiency of shallow seismic detection.The application result shows that spark source has a good applicability in shallow seismic detection for coastal tidal flats.

The study of the resolution improvement of Radon transform is one of the research hotspots in seismic data processing area.The commonly-used resolution improvement methods are carried out in the frequency domain.However,the weighting of the Radon model in the frequency domain is coupled,and it will impose the same weight on all the events,leading to the artifacts generated by high energy seismic events.This paper presents three resolution improvement methods of Radon transform in the time domain:Iterative Shrinkage Thresholding (IST),Fast Iterative Shrinkage Thresholding (FIST) and Sparse Radon Transform Iterative Shrinkage (SRTIS),with a comparison of their compute efficiencies and results.Synthetic data and real data test results show that SRTIS is superior to the other two methods in computation effect and efficiency,and it has a better multiple attenuation capability.

Due to the lack of layer, the constant change in borehole formation, the fewer logging curves in key intervals, the complex borehole environment, the complex relationship between logging response and reservoir parameters and some other factors, the logging interpretation of horizontal well in shale gas is difficult. Aimed at tackling this problem, the authors adopted the evaluation technique flow of "Formation method of horizontal well logging-Analysis of response differences between horizontal wells and between horizontal and vertical wells-Correction of horizontal well curves-Parameter evaluation method based on vertical wells" to evaluate TOC in shale gas for horizontal wells. In the logging evaluation, in view of the complex response law, the histogram method is used to analyze the logging response law and, in consideration of the fact that there are fewer logging curves for horizontal wells in the logging evaluation, a dual information fusion method is proposed based on combination with curve overlap method so as to comprehensively utilize the logging curve information. The results show that this method can correct horizontal well logging curves based on fully analyzing the logging response differences, and the dual information fusion method has the advantages of full use of logging information, high accuracy of evaluation method and simple operation.

Since the application of the time-frequency analysis method in the field of geophysics,it has been favored by geophysicists and is widely used to detect faults and cracks.Therefore,seeking for time-frequency analysis methods with higher precision has become the goal pursued in the field of seismic signal processing.The improved short-time Fourier transform method has low accuracy of time-frequency analysis due to its own window function limitation.In order to improve the time-frequency resolution to a greater extent,the authors squeezed the time-spectrum values after the improved short-time Fourier transform,and developed synchronous extrusion improved short-time Fourier transform.The synthetic signal analysis results show that synchronous squeeze improved short-time Fourier transform has higher time-frequency convergence,and can more accurately characterize the time-frequency characteristics of the signal.The theory shows that the high-frequency components of seismic data can accurately engrave tiny secondary cracks,and ant tracking technology is an effective means to detect crack and fault information.Therefore,based on the high-resolution time-frequency analysis method and the ant tracking technology,the authors predicted the three-dimensional data volume of the South China Sea by cracks.The results show that the method can describe the micro-cracks and associated folds well,and the recognition accuracy is obviously improved as compared with the algorithm of the traditional ant tracking method,thus proving the effectiveness and practicability of the proposed method.

Mahalanobis distance is a multivariate outlier detection method. At present, there are many outlier detection methods based on Mahalanobis distance. The purpose of this paper is to compare the advantages/disadvantages of various Mahalanobis distances in identifying multivariate outliers and to select a more suitable method for identifying multivariate anomalies. The authors selected 1∶500 000 stream sediment data in the East Kunlun Mountains of Qinghai Province to compare the effects of four methods: classical Mahalanobis distance, robust Mahalanobis distance based on minimum variance determinant (FMCD), robust mahalanobis distance based on Adaptive minimum variance determinant (Adaptive), and robust mahalanobis distance based on Comedian (Comedian) in identifying Cu, Co, Cr, Ni, V, Fe; Cd, Cu, Mo, Pb, Zn, Ag and three association outliers of Au, As, Sb. The result shows that the Comedian method is the superior, while the classical method is the worst. So Comedian method is the most effective multivariate outlier detection method in this area.

The discontinuity characteristic of fluvial facies sandstone reservoir due to lithology,physical property and micro-structural changes is an important factor that hinders fluid flow and affects the efficiency of injection and production.Therefore,the study of these discontinuity characteristics is of great significance for oilfield development.Such discontinuous features usually appear as seismic amplitude and waveform changes,distortion of seismic phase axis,et al.Since the scale of discontinuous features is usually smaller than the resolution of seismic data,it is difficult to accurately identify them by conventional methods.Model forward analysis found that curvature attributes have high detection accuracy for sand body discontinuity.The application of reservoir unit in an oilfield in Bohai shows that the reservoir discontinuity detection results with curvature attributes are consistent with tracer test results of the later production dynamics,which verifies the reliability of the method and provides a powerful support for the efficient development of the oilfield.

The staggered sampling grid can automatically ensure that the electromagnetic field distribution obeys the law of energy conservation. Based on the staggered sampling grid, the authors deduced the two-dimensional finite difference forward process of magnetotelluric survey, and realized the two-dimensional forward program. Compared with one-dimensional analytical solution, the algorithm is proved to be correct and has high accuracy. Then, using the finite memory quasi Newton optimization algorithm, the authors realized the staggered sampling grid finite difference two-dimensional inversion. The correctness of the inversion algorithm was verified by theoretical model inversion, which shows that the efficiency of quasi Newton inversion with finite memory is better than that of nonlinear conjugate gradient. Finally, the deep structure of the survey area was found through the inversion and interpretation of the magnetotelluric data from Guanegou in Dangchang County, which shows that the algorithm has strong practicability.

To enhance the precision of slowness extraction of component waves in array acoustic logging data,the authors,based on simulated annealing algorithm and the theory of slowness-time coherence (STC) method,put forward a new method to process array acoustic data by combining simulated annealing algorithm with slowness-time coherence method.The core of the algorithm is to transform the correlation coefficient of slowness-time coherence method into the energy function of simulated annealing algorithm so that the global optimization capability of simulated annealing algorithm can be utilized to extract the slownesses of component waves.For compressional wave,the energy ratio of short window versus long window method can be applied to the computation of arrival before annealing,so that the two-dimensional search can be simplified to one-dimensional;for other component waves,the algorithm is used respectively to extract the slownesses by two-dimensional search of slowness and arrival.Examples show that,compared with conventional compressional wave logging,the precision of the processed results of compressional wave is 9.94% better than that of conventional STC;the results of shear wave have a difference of 0.29% to those of conventional STC while the difference of Stoneley wave is 0.42%.The algorithm can enhance the precision of slowness extraction of component waves to a certain extent,performing well in application.

The aero full tensor magnetic gradient data contain complex motion noise, which is distributed from low frequency to high frequency in the spectrum, and is mainly white noise. So, how to effectively suppress the motion noise is a great challenge. The traditional digital filtering can only filter the noise with the specified frequency band, but it can not effectively separate the noise mixed in the full tensor magnetic gradient useful signal. In view of the fact that Kalman filter is a fast, efficient and real-time optimization estimation method, the authors applied it to the aero magnetic full tensor gradient data processing, and built the state equation and observation equation reasonably. Model test proves that the method is effective and can be applied to real-time processing of aeromagnetic full tensor gradient data.

In this paper, the authors analyzed the suitability of 2D nonlinear conjugate inversion method in railway tunnel AMT exploration under complex topographic and geological conditions. Based on typical modeling and inversion research, researchers can find out the best key parameters to control inversion algorithm so as to avoid fake abnormalities shown on inversion results. Researches show that 2D nonlinear conjugate inversion works well in railway tunnel AMT exploration. If the true model is like the model type described in this paper, inversion result can be efficiently improved by inverting TE&TM mode data, inverting frequencies less than 1 000 Hz, using small smooth factor and choosing the half space initial model close to the shallow layers' resistivity.

Overburden pressure is the source power of sedimentary compaction,and is also the key data to compute core pressure.This paper shows density variation with overburden pressure and core pressure,the effect of different thicknesses of mudstone on overburden pressure and core pressure.It is proved that the maximum core pressure variation is 0.02 while density variation of mudstone is 0.3 g/cm³ from 100 to 400 m,and overburden pressure is almost the same by density integration which is filtered form 3 to 250 Hz,which represents low-frequency tendency.Therefore,on the basis of the relationship between the effective stress of the normal compacted formation and the pressure of the overlying strata,a fast method was established for converting the pressure field according to the well-controlled seismic layer velocity field,which was verified by multiple drill holes in some structure of West Bohai Sea,thus satisfying rapid exploration.

During the acquisition of ground penetrating radar (GPR) data, noise would inevitably be mixed in by the influence of external factors, which seriously interferes with the identification and interpretation of effective echo. Therefore, the authors used the bilateral filtering algorithm to remove noise from ground penetrating radar data. By adding White Gaussian Noise to the forward record of ground penetrating radar to simulate the measured ground penetrating radar record, the synthetic record containing noise was filtered by bilateral filter. The results show that the bilateral filtering algorithm can remove most of the White Gaussian Noise, highlight the effective echo information and increase the peak signal-to-noise ratio (PSNR) from 15.845 1 to 22.147 7. Furthermore, the bilateral filter was used to filter the measured records. The filtered results show that the noise removal effect is better, which indicates that the bilateral filter could be effectively applied to the denoise of ground penetrating radar data.

This study was based on soil geochemical survey data obtained in Beijing plain. The methods of mathematical statistics, factor analysis, correlation analysis and regression analysis were used to study the horizontal and vertical distribution characteristics of soil elements, and the influencing factors were discussed. The result shows that the content of CaO, MgO, Na₂O, Hg, Cd, Sr, Ba, and Sn in soil is high and that of Sb, As, Th, W, Br, U, I, Mo and organic matter is low. The result of R-type factor analysis shows that factor F1 reflects the characteristics of the original soil background, factor F2, factor F4 and factor F6 reflect the influence of human activities on the distribution characteristics of soil elements, factor F3 reflects the basic information of soil parent material, and factor F5 reflects the basic characteristics of soil parent rock. The vertical distribution characteristics of elements were modeled by regression analysis. The regression coefficient R² is 0.542~0.960, and the effect is good. From the regional scale, it is preliminarily determined that the depth of human activities on Cu, Hg, Pb and Zn is 150~200 cm, and that on N, P, S, Se, and organic matter is 50~100 cm. In general, the content of 39 elements such as Se, Bi, Li, organic matter, Mo and W in cinnamon soil is higher than that in alluvial soil.The relationship between the values of 29 elements such as As, Cd, Cr, Ni, N and B in different soil textures are in order of sandy loam<sandy clay loam<clay loam<loamy clay. The content of Cd, N, P and organic matter in cultivated soil is significantly higher than that in forest land. The content of harmful metals and nutrients in the soil of the central urban area is higher than that in the suburban area.

Based on the land quality geochemical survey data obtained in the Zhelong-Gasa area, Yunnan Province, the authors studied geochemical characteristics and main influencing factors of Cr and Ni in surface soil and analyzed Cr and Ni content characteristics of agricultural products. The results show that the content of Cr and Ni in the surface soil is mainly controlled by the geological background. The content of Cr and Ni in the soil developed in the Guangshan-Pingyakou rock mass (σ) of the study area is significantly higher than that in other strata. The medium values of Cr and Ni in different types of soils are quite different, and land use also affects the content of Cr and Ni in the soil. The Cr and Ni values of agricultural products such as corn, citrus, tea, sugarcane, bananas, and walnuts in the study area do not exceed the food safety standards. Only the values of 11 rice Cr samples exceed the Cr content standards set by national standards,accounting for 11.3% of the total rice samples. The overall evaluation of agricultural products in this area shows safety. The area of agricultural land such as paddy field, dry land, garden land and grassland in this area is 554.73 km², of which, the area of safety area is 408.61 km², accounting for 73.66%, the area of risk area is 112.96 km², accounting for 20.36%, and the area of control area is 33.16 km², accounting for 5.98%.For some areas with soil Cr and Ni pollution risk, measures are proposed such as soil and water conservation, fertilization adjustment, and water-dry rotation to prevent and control pollution risks.

In this paper, the Wuqing Sag, a fourth-level tectonic unit where the water source in the north of Wuqing is located, was selected as the research area, and 95 groundwater sampling points were set up. Fluoride groundwater in the first aquifer was taken as the study object.Based on hydrogeological survey and sample analysis, the authors investigated spatial distribution of F^- concentrations as well as evolution feature and genesis of fluoride groundwater in shallow aquifer from Wuqing Sag by means of hydrogeochemical plot, statistic analysis and geochemical modeling. The results show that the mass concentration of F^- in shallow groundwater in the study area is generally high, the distribution trend is that the concentration in the NW-SE direction is the highest, and the concentration gradually decreases toward both sides, that hydrogeochemical types of groundwater with high F^- concentration are relatively complex, and have the characteristics of weak alkali, high sodium and low calcium, and that the formation of high-fluorine water is mainly controlled by the strong evaporation and concentration, fluorite dissolution, calcite-dolomite precipitation, and F^- desorption in this area.

The microtremor survey method is a new environmental protection geophysical exploration technology with strong anti-interference ability, large detection depth and wide application range. It has been widely used in structure, boulder, karst cave and some other fields. However, the single point data acquisition method represented by circular array is limited by the field conditions. It is difficult for this method to achieve high-efficiency and high-density data acquisition of long profile. This paper presents an efficient data acquisition technology based on linear array with multiple coverage in order to solve this problem. Based on the idea of multiple coverage observation system in seismic exploration, the dispersion curves of multiple measurement points can be obtained by setting up a linear array at one time, which greatly improves the utilization rate of single station data acquisition. The feasibility and effectiveness of the technology were studied by applying the technology to the detection of boulders along subway of Fuzhou airport. The experimental results show that the high-efficiency data acquisition technology based on linear array multiple coverage greatly improves the efficiency and density of microtremor data acquisition, effectively improves the detection accuracy and detection depth, and provides a new array layout scheme for urban complex ground environment.

Aiming at tackling the problem of whole-space transient electromagnetic response signal identification in water-bearing goaf and based on induced electromotive force (EMF)-apparent resistivity and time-depth conversion relationship, the authors obtained the spatial distribution law of apparent resistivity with depth variation of the whole sector by using the finite element numerical simulation and field measurement method, extracted the EMF attenuation curve of the measuring point in the low resistance abnormal area, and calculated the voltage rise amplitude of the measuring point varying with the detection angle. Based on the above research, the authors carried out the drilling verification and borehole peeping, and analyzed the content of the drilling water samples. The results show that the transverse angle consistency of transient electromagnetic response of water-bearing goaf is higher than that of vertical depth, and the rising amplitude of EMF in the abnormal region of low resistance is opposite to the difference of induced voltage, which shows a sharp increase in the initial stage of secondary field observation followed by slowing down, reaching more than 10 times on the whole. Drilling engineering and geochemical exploration analysis further verify the geophysical exploration results.