As a method for effectively reducing the velocity model of the subsurface media,seismic tomography provides a reliable initial velocity model for full waveform inversion.The finite frequency characteristics of seismic wave propagation are realized from primitive ray toe to phase shift travel time tomography and instantaneous travel time tomography.From the acoustic wave equation to the elastic wave equation and from the isotropic medium to the VTI,TTI media,the simulation of the real underground medium is realized.The morbidity of mitigating tomographic inversion has also been a research hotspot.The commonly used methods have regularization,and the sensitive nucleus of Gaussian beam tomography has replaced the traditional ray-sensitive nucleus.Furthermore,in order to avoid the dependence of the accuracy of the imaging results on the true depth of the reflection bits on the common imaging gather,the angular domain double differential reflection tomography can converge stably and efficiently to the accurate migration velocity model.At present,tomography is gradually transitional to anisotropic media,data used are transitional from VSP to WVSP,and a single waveform is developed into multiple waveforms combined inversion.However,problems related to resolution and computational efficiency still require attention.

Located along the Au-Pb-Zn-Cu-Fe-P-barite-coal-coal bedgas metallogenic belt in Qujing-Shilin fold thrust zone, the Daibu Town-Deze Town area of Yunnan Province is an important phosphorus, lead and zinc ore concentration area in Southwest China. Based on stream sediment geochemical Survey at the scale of 1∶50 000 in the Daibu Town-Deze Town area, the authors made comparison and analysis of geochemical characteristics of different formations, with the purpose of confirming the enrichment and dilution regularity and assemblage characteristics of regional elements. The study focused on the Xiaomiga No. HS-23-A₁ geochemical anomaly of P-Pb-Zn-Mo and Tengziwa-Reshuicun No.HS-24-A₁ geochemical anomaly of Pb-Zn-Au, and found the following phenomena: the HS-23-A₁ anomaly is induced by the ore-hosting horizon of third member of Lower Cambrian Dengying Formation and Cambrian Qiongzhushi Formation;the HS-24-A₁ anomaly is caused by lead-zinc veinlet,whereasthe Au anomaly is due to the secondary enrichment in the weathering crust.The Xiaomiga No. HS-23-A₁ geochemical anomaly serves as a good prospecting target for deep orebodies.Two phosphorus orebodies were delineated, but the Tengziwa-Reshuicun No.HS-24-A₁ geochemical anomaly of Pb-Zn-Au is relatively not ideal.Finally, the authors summarized the prospecting indicators of phosphate and lead-zinc deposits. The results obtained by the authors lay a foundation for further prospecting work.

The geological structure of Yinchuan Plain is a Cenozoic fault basin, which belongs to the western marginal zone of Ordos block, and is sandwiched between the Helanshan uplift belt and the Taole-Hengshanbao thrust belt. It is also subjected to the east-west tensile stress of the Ordos block and the northeastward compression stress of the Alxa micro-continent, which forms complex geological structural features of this area. As an important part of the Tibetan block, the Ordos block and the Alxa block, and the important component of the north-south seismic belt, the Yinchuan fault basin has become one of the more active boundary structures in China’s mainland, and had many strong earthquakes in history. In order to interpret the deep geological structure of the Yinchuan fault basin, the authors employed 1∶200,000 regional gravity data, drilling data, seismic section, and magnetotelluric profile data as constraints to perform 2.5D human-computer interaction inversion in Yinchuan Plain. Based on this result, a deep 3D geological model of the Yinchuan Plain was constructed, which laid a solid foundation for regional stability evaluation, exploration and development of geothermal resources.

The structure in the west of the Weihe Basin is complex. At present, there are different views on the basic geological problems in such aspects as the division of the tectonic units, the characteristics of stratigraphic development and the properties of basement. In this study, the distribution characteristics and basement properties of the sedimentary strata in the western part of Weihe Basin were inferred by using four newly implemented magnetotelluric (MT) sounding profiles in Baoji area, in combination with the gravity data and through the comprehensive interpretation of gravity and electricity. The results show that, along the route from Longxian to Fengxiang, the resistivity anomaly is low, the gravity is high, the Cenozoic sediments are thin, and the basement is shallow. The Cretaceous strata are exposed in some areas, and the basement of the area is dominated by the Mesozoic strata. In Qianyang area, there are high resistivity value and high gravity value, and the surface outcrop is complex. There exist Cambrian, Ordovician, Triassic, Cretaceous, Jurassic and some other strata, and the basement is composed of Mesozoic-Paleozoic-Proterozoic strata. In the west of Fufeng, south of Qishan, the resistivity value drops sharply from the north and south sides, and the basement is assumed to be composed of metamorphic rocks. The northern part of Baoji to Meixian area is characterized by high resistivity and gravity, and the northern part of Baoji to Meixian area has partly exposed Cretaceous strata with Paleozoic-Proterozoic basement. The south of Baoji to Meixian area is characterized by high resistivity and low gravity. There is a large area of granite outcrops, with the basement composed of granite.

Based on the comprehensive utilization of drilling data,logging data and 2-D seismic data,the authors hold that the tight reservoir of Yanchang Formation in Heshui area of Ordos Basin has developed a complex fault system consisting of strike-slip faults,fault damage zones and small-scale fractures,which together affect the heterogeneity and flow capacity of underground reservoirs,thus having an important impact on oil and gas production.So faults,fault damage zones and natural small-scale fractures should be treated as a system to analyze the fracture characteristics of ultra-low permeability reservoirs.The authors hold that only considering small-scale fractures is obviously not comprehensive.This understanding has important implications for the study of fractures in ultra-low permeability reservoirs in Ordos Basin.

Because of complex reservoir forming conditions,strong heterogeneity and indistinct regularity of conventional logging response,it's difficult to conduct exploration effectively in the carbonate reservoir.The effectiveness evaluation of fractured reservoir is the main problem in the exploration and development of deep oil and gas.Seismic survey is limited to identitying small scale fractures or faults because of low resolution,and it is difficult for conventional logging method to accurately evaluate the geological characteristics because of the shallow investigation depth.The dipole shear wave imaging technique has been developed in recent years,which can image borehole acoustic reflectors within the range of 20~30m based on low frequency of dipole shear wave.Monopole radial profiling of compressional slowness can be used to retrieve P-wave velocity variation in well bore within 1m,which can indicate the reversibility of the reservoir.The dipole shear wave imaging is a good way for finding the extension of the wellbore fractures and the concealed fractures near the well,and monopole radial profiling of compressional slowness can reflect the change of P-wave velocity near the wellbore.In a comprehensive way,the reservoir with such characteristics as well developed fractures,long extension of fractures or existence of concealed fractures near the well bore and remarkable variation of compressional slowness indicates great potential for reservoir reconstruction.This method was applied to processing several wells in Hexiwu Qianshan in Huabei Oilfield,and the results correspond well with the results of liquid production after the reservoir reconstruction,and hence the method is worthy of further popularization and application.

Multi-channel transient electromagnetic data suffer seriously from cultural noise, and removal of periodic cultural disturbance has been a major problem in the multi-channel transient electromagnetic method. In some cases with only quite a few power lines configured regularly, the power line interference can be reduced by exchanging the receiver and source. The method by reversing source current polarity then stacking them period-by-period works better for step-current source. When only homogeneous earth is considered, the perpendicular electric component, which is in fact noise, can be measured and then subtracted from the in-line electric component. Digital recursive notching is a relatively robust way in which the periodic noise can be suppressed. It is well known that recursive notching is very fast; however, holes resulting from pre-deconvolution notching and transient response of digital recursive notcher has to be highly regarded. In this paper, several key points in removal of periodic power line noise in multi-channel transient electromagnetic data using digital recursive notch are studied. First of all, a modified version of so-called zero-pole digital recursive notcher design method, where filter coefficients are evaluated from notch width that makes significant physical sense and make analysis more clear, is proposed. After that, research on post-deconvolution notching, which directly deals with earth impulse response, is conducted. In addition, factors influencing transient response and notch result, such as notch width, initial conditions, and shape of earth impulse response, are analyzed. The results indicate that appropriate selection of initial conditions can effectively reduce the transient response of digital recursive notcher and thus remove periodic noise in earth impulse. Finally, reasonable result is obtained by applying the post-deconvolution digital recursive notch to real field data.

The time domain finite element algorithm has been widely used in airborne electromagnetic three-dimensional forward modeling. However, due to the large airborne electromagnetic measurement area and dense sampling, the forward calculation is huge, and the traditional serial algorithm cannot meet the calculation efficiency requirements. In view of such a situation, the authors carried out parallel acceleration algorithm research to solve the problem of insufficient computational efficiency. Based on the limited range of influence of aviation electromagnetic system, the local grid technology is used to divide the computing task into multiple sub-grids, that is, a set of grids for each source, and the forward calculations of each grid are independent of each other, and hence no data dependency is existent and there is good parallelism. In this paper, MPI technology is used to allocate multiple sub-grid forward tasks, and parallel computing is performed on each process. For each forward subgrid, in the forward modeling of the time domain finite element algorithm, the parallel matrix is calculated by OpenMP technology. The numerical simulation results of the typical electrical model show that the MPI+OpenMP parallel forward algorithm developed in this paper can effectively improve the forward speed, and the maximum acceleration ratio can reach 10 times.

Filtering is one of the crucial technologies for data processing in airborne gravimetry. Aimed at the wavelet filtering especially, the authors developed the wavelet low-pass filter for data processing in this paper. Based on the wavelet packet analysis, the wavelet packet tree was optimized according to the signal frequency range of corresponding estimated wavelet packet decomposition level, the desired low-pass cutoff frequency and the node’s arranged order on the basis of the “frequency” order of the wavelet packet coefficients from the low frequencies to the high frequencies. The main characteristics of the orthogonal or the biorthogonal wavelets were analyzed, and the new threshold processing schemes were proposed in this paper, The authors made the experimental researches on filtering GT-airborne gravity data using the wavelet filter. The results show that the discrete Meyer wavelet’s filtering has achieved the best effect among the wavelets available, and this wavelet filter for airborne gravity data has almost as good satisfactory filtering effect as GT-1A result, with the root-mean squared difference between 0.2 mGal and 0.3 mGal in comparison with GT-1A result.

In order to finely implement the characteristics of the Jianbei structure and fault system,explore the spatial distribution law of Jurassic strata,improve the imaging accuracy of breakpoints and sections,and implement the distribution of small faults and concealed faults so as to provide strong support for bedrock lithologic traps,the authors used high-precision seismic exploration technology with low-frequency vibrator "two widths and one high" (wide azimuth,wide band,high density) in this area.This technology can record wave field information more completely,with low frequency information and less space and false noise.It is conducive to the study of broadband processing and azimuthal anisotropy of thin interbedded reservoirs.In this paper,from the aspects of wave field characteristics,signal-to-noise ratio and frequency of the region,the authors used the low-frequency vibrator "two widths and one high" wide-band,wide-azimuth high-resolution amplitude-preserving processing technology to image small faults and bedrocks.The fine characterization shows that the "two widths and one height" method has unique advantages in wideband and wide-range data processing.

In this paper,the channel sand body of Fuyu oil reservoir in Y₅ well area of Zhaoyuan area in northern Songliao Basin was chosen as the research object.In view of the phenomena that the sand body thickness is thin,the lateral change is prominent,and the seismic response characteristics of the sand body of the same thickness are inconsistent,the authors adopted the time-frequency analysis technique based on the simulation analysis of the seismic response characteristics of the target sand body.The generalized S transform was used to optimize the sensitive frequency of different thicknesses and combined sand bodies in the frequency domain,and the data were reconstructed based on the sensitive frequency to eliminate the sand.The body and the seismic profile characteristics were inconsistent,and it was better to predict the sand body distribution by seismic attributes.The research results show that using the sensitive frequency to reconstruct the seismic attributes extracted by the data body can effectively improve the prediction accuracy of the thin-layer channel sand body and greatly reduce the risk of oilfield exploration and development.

With the increasingly refined and complicated exploration and development goals,the least-squares inverse-time migration based on inversion theory has gradually become the current development trend.In order to make the least-squares reverse-time migration better for the exploration and development of oil and gas reservoirs,analyzing the imaging effects under different conditions helps to guide the processors to make appropriate adjustments in the actual data processing.For this reason,in view of the migration velocity error and the noise in seismic data in the actual exploration process,the authors made a comparative study of the imaging effects of least-squares reverse-time migration under different conditions.The results show that,in the case of systematic errors in migration velocity,the imaging depth of interface will have errors,and it is difficult for the imaging profile to reflect the actual structure;the influence of smoothed migration velocity errors on least-squares reverse-time migration is much smaller than the systematic error of migration velocity,and proper smoothing can improve the imaging quality,but excessive smoothing can affect the imaging quality;the least-squares reverse-time migration can suppress part of the noise;nevertheless,as the noise in the seismic record increases,the weak reflection gradually cannot be resolved,and it is difficult to reflect the underground structure.

Conventional seismic facies analysis based on seismic sedimentology principle mainly uses seismic slicing technology to extract RMS amplitude attributes along the target layer.When the signal-to-noise ratio of seismic signals is low and the target layer is thin,the accuracy and reliability of seismic facies analysis will be easily affected.In this study,on the basis of the principle of seismic sedimentology,the feature vectors of seismic waveforms were extracted along stratigraphic slices,and then the Agglomerative Hierarchical Clustering (AHC) method was introduced to classify seismic facies.Waveform AHC is an unsupervised machine learning algorithm.Compared with the traditional method of seismic facies analysis for stratum slices,the method based on waveform clustering considers the amplitude, phase and frequency attributes of seismic signals synthetically through the change of waveform characteristics.It has better anti-noise capability and higher horizontal resolution.The stability and applicability of this method have been proved by physical model data testing and practical data application.It has been proved that this method has a good capability of distinguishing sedimentary facies characteristics,and hence it is a new kind of reservoir facies analysis tool and has a good application prospect.

The leaching of elements of mobile forms is one of the effective techniques in deep penetrating geochemistry in search of concealed deposits. The leaching time as an important factor has a great effect on the leaching results because of the different action modes of extractant, target elements and minerals. The total reflection X-ray fluorescence spectrometry (TXRF) was used to determine the change of the leaching amount of mobile forms of Cu, Pb, Zn, Ni and Mn with the leaching time. The results showed that the leaching amount of analytical elements increased rapidly within 1 hour, increased at a high rate within 7 hour and reached a balance at 24 h. The nonlinear kinetic model of w_t = w₁ exp(-k₁t) + w₂ exp(-k₂t) was established to simulate the leaching course for mobile forms of elements adsorbed by two forms in soils. In the equation, k₁ which is relatively fast represents the leaching rate of the non-obligate adsorption of mobile forms of elements such as ion form, electrostatic adsorption form, and existence in the form of nanoscale metal particles, while k₂ which is relatively slow represents the leaching of the obligate adsorption of mobile forms of element, such as clay adsorption form, weak binding form of iron and manganese oxide or organically bound form.The kinetic model further provides a basis for exploring the leaching mechanism of mobile forms of elements.

At present, the dilemma of long sample testing cycle, waiting and prompting reports is a common phenomenon. In the past three years, the mineral geological survey project in southwestern Guizhou Province mainly focused on Carlin-type gold deposits, and the project team introduced visual colorimetry which was proposed in the 1990s.Through repeated comparative tests, part of the method was improved and equipment was upgraded, then a set of integrated analysis box was developed, which is convenient for field transportation and use. Compared with the test results of the same samples in the laboratory, it is shown that the performance indicators can meet the needs of rapid qualitative judgment such as detection limit and test accuracy. These results prove that this means can effectively assist the frontline geologists in timely judging the newly discovered mineralization phenomena and new ore spots in the field investigation process, thus improving the effectiveness in gold prospecting work.

In view of the problem of residual signal (also known as energy leakage) in the noise profile of the existing conventional denoising method in the parameter selection,this paper proposes the energy leakage recovery method of adaptive K-SVD to achieve effective recycling of signals.Firstly,a high-quality sample is obtained by using traditional methods such as wavelet threshold and fx domain denoising to perform dictionary construction,and then the correlation coefficient matching criterion is introduced to sparsely decompose the residual profile so as to realize the secondary separation of random noise and residual effective signal.The experimental results show that the proposed algorithm can better balance the denoising and amplitude preservation of seismic signals and has adaptability.

Gaussian beam tomography uses the Gaussian beam operator to compute the travel-time tomographic kernel function instead of the conventional ray tomographic kernels,which can improve the accuracy and stability of velocity building.However,the absence of prior geological information sometimes leads to the lack of geological understanding of the results.On such a basis,by introducing the preconditioned model regularization operator,a method of Gaussian beam tomography velocity building under the constraint of structure-guided filter is derived,whose key is to construct the structure-guided filter operator.In this paper,structure tensors were calculated by seismic profiles,and geological structure features were introduced by anisotropic diffusion smoothing operators as regularization constraints for inversion.This method is entirely data-driven and achieves the "soft constraint" of tomographic inversion,which not only reduces the issue of multiple solutions of inversion but also improves the inversion resolution,and hence can obtain a reasonable velocity model with geological recognition.The validity and practicability of the Gaussian beam tomography velocity building with structure-guided filtering were verified by its application to synthetics and practical data.

Thin inter-bedded reservoirs,lithologic reservoirs and subtle reservoirs have gradually become the focus of exploration and development,which requires higher resolution processing methods and fidelity processing.In the process of improving resolution of conventional seismic data processing,the focus is mainly concentrated on the study of improving resolution methods,and there is a lack of systematic and comprehensive quantitative evaluation and analysis methods and software modules for improving resolution effect.In order to meet the urgent need of improving resolution quality monitoring,the authors carried out the study and development of evaluation methods and technical modules for improving seismic resolution effect so as to optimize the processing technology,process and parameters of improving resolution efficiently,comprehensively and reliably monitor the processing process of improving resolution,and realize the quantitative evaluation and analysis of the effect of improving resolution processing of seismic data.Quantitative evaluation method of improving resolution effect was applied to Shawan Formation thin layer reservoir in Chepaizi area.Quantitative evaluation and analysis of the effect of whole process of improving resolution processing were carried out.The capability of identifying thin layer has been greatly enhanced after improving resolution processing,and ideal results have been achieved.

The main noise source of time-domain airborne electromagnetic survey is sferics that affects the quality of data. In practical work, how to remove sferics efficiently and quickly is the key to data preprocessing. Previous studies of trimmed mean/median filter have a good effect on sferic noise removal. However, there are some problems with single-window-filter. Small window filter does not completely remove the sferics, while large window filter can remove the sferic noise well, but the data at the power on, peak and power off will be over-averaged. Therefore, this paper proposes the hybrid window trim-mean filter, that is, small window parameter filter is adopted for the data at the power on, peak and power off every half cycle, and large window parameter filter is adopted for other data. This method can ensure the trend of data change and better remove the airborne noise at the same time. The removal of sferic noise can not only improve the SNR of data but also increase the exploration depth and provide high-quality data for data processing.

This study combines the deep learning with the identification of gravity anomaly body. Based on the CNN (convolutional neural network) which has been gaining its use in the past several years in the field of image identification, the contour image of gravity signal is taken as the unidentified image, while the space parameters of the gravity anomaly body will be identified through CNN. In the training phase, a large number of the 3D anomaly bodies are generated with random variation of parameters, then the network is fed with parametric labels and the computed gravity contour images. The testing is performed with generated testing models to estimate the performance of the trained model. The trained CNN accuracy shows excellent accuracy in the identifications. Then the CNN model is tested with measured main gravity anomaly data of Kauring area in West Australia, and the identified parameters of the 3D anomaly body are compared with known results. It is shown that the generalization of CNN can handle identification of the measured gravity data.

In this paper, the isoline tracking algorithm was studied and the corresponding software was developed. This study improves the function of geophysical data processing and interpretation system. Also, it provides method and technical support for the study and development of all independent domestic software. Based on grid data access interface and plug in technology and combining contour features, the authors developed the software for contour tracking by building a progressive tracking algorithm model. The developed software unifies the grid data access interface and maintains the integrity of system functions. Tests on real field data demonstrate that the tracking algorithm has reached the international general software level in both effect and efficiency, and can meet the requirements of system design.

There are multiple combinations of sandstone and mudstone interbeds and also plenty of coal seams in the middle-shallow strata of Mahu sag's slope zone, due to the slow slope background and shallow lake environment of water oscillation since Jurassic. In addition, the lithologic reservoir can be found in the zone, but the shielding effect of coal seam makes it impossible to predict the reservoir, due to the unclear response of the thin interbed from seismic and acoustic logs. Therefore, the wave impedance inversion cannot distinguish sandstone from mudstone clearly. In view of such a situation, the technique of Pseudo-acoustic curve reconstruction was used in this study. By analyzing multiple well logs, the density and neutron curves, which can weaken the influence of coal seam and reflect the characteristics of sandstone and mudstone interbeds, were selected to rebuild pseudo-acoustic curves and then perform inversion with the rebuilt curves, thus improving greatly the accuracy of reservoir prediction.

Based on the sampling data of soils, rocks and agricultural products in the Jiucheng-Jiemao area, Yingjiang County, Yunnan Province, geochemical characteristics of selenium in soils and main influencing factors were studied, and the characteristics of selenium content in agricultural products were analyzed. The results show that the range of selenium content in soils of the study area is 0.01×10 ^-6~2.22×10 ^-6, the average value is 0.23×10 ^-6 and the area of selenium-rich soil is 73.41 km ², accounting for 17.47%, that selenium is mainly in the form of residue state, but the percentage of water soluble state and ion exchange state which can be effectively absorbed by crops is only 3.32%, and that the content of selenium in soil is mainly influenced by soil-forming parent materials, silica-sesquioxide ratio, organic matter and pH value. According to the relevant evaluation criteria, a total of fifteen coffee beans, one Australian nut, two rice and five sugarcanes can meet the requirements of safe selenium-rich food. The safe selenium-rich rate of four kinds of agricultural products is 100%, 10%, 1.32% and 16.67% respectively, which is basically consistent with the distribution position of selenium-rich soil.

One of the main problems in the ecological researches is natural environmental radioactivity. In this study, the activity concentrations of naturally formed ²³⁸U, ²³²Th, ²²⁶Ra and ⁴⁰K radionuclides were measured for various types of soil samples collected from Guangdong Province. Samples in 49 siteswere selected within the study area. The concentration of radionuclides of ²³⁸U is in the range from 17.9 to 209.1 Bq/kg, with the average value being 84.3 Bq/kg; that of ²³²Th varies from 10.6 to 263.8 Bq/kg, with average value being 103.0 Bq/kg;that of ²²⁶Ra varies from 12.0 to 206.0 Bq/kg, with average value being 77.7 Bq/kg; and that of ⁴⁰K varies from 15.3 to 1557.6 Bq/kg, with average value being 463.3 Bq/kg. The gamma absorbed dose rates in air is in the range of 27.2~265.9 nGy/h, with an arithmetic mean of 126.8 nGy/h, while the annual effective dose rates (AEDR) are in the range of 33.3 to 326.1 μSv/y, with an arithmetic mean of 155.5 μSv/y. The calculated values of radium equivalent activity (Raeq) and external hazard index (Hex) for the soil samples in the study area is 260.7 (33.5~619.0) Bq/kg and 1.2(0.15~2.8), respectively. Sample sitesare assigned to regional bedrock, geomorphic landscape and soil type, respectively, resulting in three categorical variables. Random forest regression and correlation analysis show that the bedrock influences the levels of natural radioactivity in soils most seriously, followed by the soil type and then by the geomorphic landscape. The activities determined in Guangdong Province are generally higher than the average values of China and the values abroad, but are lower than the safe range of radioactive level.

The 0~20 cm surface soil, the horizontal profile soil and the 0~200 cm vertical profile soil samples were collected systematically to determine the content of soil fluoride and related indicators, and the distribution characteristics and influencing factors of soil fluorine content in surface soil and profile soil were studied. The results show that the fluorine content in the surface soil of the study area ranges from 448×10 ^-6 to 1 009×10 ^-6, with the average content being 685×10 ^-6. The distribution characteristics of fluorine content in surface soil are obviously restricted by geological and geomorphological conditions. The soil with high fluoride background (>730×10 ^-6) is concentrated in the sub-clay of Qhb group, and the landform is flood plain.The surface soil fluorine is positively correlated with TFe₂O₃ (r=0.76), Mn (r=0.79), CaO (r=0.66) and Al₂O₃ (r=0.59), and negatively correlated with w(SiO₂)/w(Al₂O₃).In the vertical section, soil fluorine is mainly concentrated in 0~155 cm. Iron and manganese oxides are important factors that restrict the vertical distribution of soil fluorine.

In the construction of large-scale hydropower stations, a large amount of waste slag is produced and is often deposited in the nearby site, thus forming a large scale waste accumulation body. Under the condition that the thickness and trend of the slag accumulation body are not ascertained, the excessive heap load will easily cause the collapse accident, so it is very important to investigate the distribution of the slag accumulation body. In this paper, the high density resistivity method was used as the main method, and the high density resistivity method was used to verify the abnormal area and key position of the electrical method. At the same time, drilling holes were arranged at the site for comparative analysis. The results show that the high density electrical processing results are in good agreement with the results of transient Rayleigh surface wave method and borehole data. Through this investigation, the authors basically detected the distribution of abandoned slag deposits. High density electrical method and transient Rayleigh surface wave method are effective methods for investigating slag deposits.

Rocks along the Three Gorges reservoir area are cracked due to the influence of structure,weathering and water-level-fluctuation area.In this paper,the finite difference forward algorithm program was used to simulate and calculate the radar response characteristics of the fractures of dangerous rock body.The results show that different inclined fractures have different GPR response characteristics.According to the corresponding relationship between model and simulation results,fractures can be identified from field measured data.Taking the geological radar detection of Banbiyan dangerous rock zone in Chongqing as a study case,the authors successfully identified the fractures of dangerous rock bodies by inferring and interpreting the field measured data of ground penetrating radar.The case study itself can be used as a reference for the detection of the fractures of the dangerous rock body in other water-level-fluctuation areas.

Under the condition of deep overburden,it is important to economically and quickly judge the complex geological problems in hydropower engineering survey.Surface wave exploration technology with field source compensation has the advantages of economy,rapidity,good stability and little interference from outside.It has been applied in many fields with good results achieved.Starting with complex geological problems and based on comparing and analyzing the detection effects of high density resistivity method,magnetotelluric method and surface wave exploration method,the authors hold that the large depth surface wave detection technology can effectively avoid the influence of complex geological conditions in surface layer,improve the detection depth and accuracy to a certain extent and solve geological problems in a certain range.

Influenced by normal fault F2 of right abutment,karst is extensively developed in a reservoir and, as a result, there exists the leakage problem. Although several anti-seepage treatments have been conducted,leakage problem still exists in the near-dam reservoir area,and the situation has been getting worse and worse. In this study. the seepage of the reservoir was detected by flow field method,natural electric field method and high density resistance method. According to the results obtained, comprehensive geophysical prospecting method can accurately obtain the location information of seepage source and seepage channel of the reservoir; the sealing quality of old tunnels is poor and there are leakage problems, which also leads to concentrated seepage and large-scale scattered immersion of the downstream side dam body; the low mountain body on the right bank of the dam has seepage entrance and may be connected with the spring water point at the foot of the downstream mountain; the F2 fault zone on the right abutment of the dam has poor imperviousness,and there exists a leakage passage connected with the concentrated seepage points at the outcrop of downstream faults.