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  • Table of Content
      10 February 2015, Volume 39 Issue 1 Previous Issue    Next Issue
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    Article
    High precision computation and numerical value characteristics of gravity emendation values arising from mass of the Earth's crust at the distance over 169 km from the observation point
    AN Yu-Lin, GUO Liang-Hui, ZHANG Ming-Hua
    Geophysical and Geochemical Exploration. 2015, 39 (1): 1-11.   DOI: 10.11720/wtyht.2015.1.01
    Abstract   HTML   PDF (7882KB) ( 583 )

    In the previous textbooks of gravitational prospecting, the computation of gravity emendation values arising from mass of the Earth's crust at the distance over 2 km from the observation point is confined only to an area of circular ring 2.0~166.7 km in breadth and the computation expressions coming into existence in the orthogonal coordinate system are adopted. China Geological Survey has generalized in recent years the computation program of gravity emendation value that adopts the computation expressions both in the orthogonal coordinate system and in the spherical coordinate system; nevertheless, the computation of gravity emendation values remains confined to an area of circular ring 2.0~166.7 km in breadth and fails to take into account the gravitation arising from mass of the Earth's crust at the distance over 166.7 km from the observation point.10 years ago, the authors deduced alone gravity expression of the hexahedron with a spherical crust form and other expressions related to the computation of gravity emendation values. After this, adopting these expressions, the authors conducted researches on high precision computation and numerical value characteristics of gravity emendation values arising from mass of the Earth's crust in pure spherical coordinate system, with the following computation achievements obtained: ① high precision computation result of "Gravity Emendation Value arising from Mass of the Earth's Crust at Distance Over 169 km From Observation Point" (GEVMECDO 169 km FOP) at the square grid 40 km in breadth on whole Earth's land and ocean surface; ② high precision computation achievements of GEVMECDO 169 km FOP at longitude and latitude grid of China's continent; ③ high precision computation achievements of GEVMECDO 169km FOP at the square grid 0.556km in breadth in local 3°×2° area along the large curved portion of the Yarlung Zang Zangbo River.Based on analyzing numerical values distribution characteristics of GEVMECDO 169 km FOP on the whole Earth's and local surfaces, the authors have arrived at the following conclusions d: ① The maximum, minimum and mean values of gravity emendation values on the whole Earth's surface are 106.990 mgal (87.877°E, 32.271°N), -41.146 mgal (166.122°E,28.327°N) and -16.439 mGal respectively; the distribution characteristics of these values are in the main consistent with the distribution characteristics of the Earth's land altitude/sea depth values. ② The distribution characteristics of gravity terrain emendation values in a local area arising from mass of the Earth's crust in large circular rings 169-1 272 km in breadth are in the main consistent with the distribution characteristics of land altitude values in this local area. These data suggest that there are high frequency components in gravity emendation values of the area with larger altitude differences,and these high frequency components with terrain altitude values have positive correlation. These facts differ remarkably from the opinions put forward by many researchers. In fact, these high frequency components result from larger altitude differences of neighboring points in a local area. ③ No mater how large the differences of altitudes /sea depths in a local area and its peripheries are, these GEVMCDO 1 272 km FOP are approximately close to a very small constant and may not be computed; ④ Where the altitude or sea depth of local area and its peripheries changes smoothly, the gravity emendation values of the whole mass of the crust over the distance of 169km are approximately close to a constant and hence may not be calculated. The results achieved by the authors have important significance for perfecting high precision computation of gravity emendation values arising from mass of the Earth's crust. The authors suggest introducing these achievements into new textbooks of gravitational prospecting and also propose to study and extend this research topic with high precision and high speed with the purpose of convenient application of gravity emendation values arising from mass of the Earth's crust on the basis of these achievements.

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    Landscape division suitable for geochemical exploration
    GUO Zhi-Juan, KONG Mu, ZHANG Hua, YANG Fan, XU Ren-Ting, WANG Cheng-Wen, WANG Qiao-Lin, SONG Yun-Tao, HAN Wei
    Geophysical and Geochemical Exploration. 2015, 39 (1): 12-15.   DOI: 10.11720/wtyht.2015.1.02
    Abstract   HTML   PDF (1051KB) ( 674 )

    According to the characteristics and requirements of the geochemical exploration in China, geochemical landscape map was compiled on the basis of the landscape classification, with the division and summarization conducted in connection with the natural geography and geographic and geomorphic conditions. The results achieved by the authors not only provide the reference material for application of geochemical exploration data and interpretation of results, but also are of guiding significance for choosing the appropriate methods and techniques.

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    Research status and development trends for geoelectrochemical methods
    SUN Bin-Bin, LIU Zhan-Yuan, ZHOU Guo-Hua
    Geophysical and Geochemical Exploration. 2015, 39 (1): 16-21.   DOI: 10.11720/wtyht.2015.1.03
    Abstract   HTML   PDF (574KB) ( 642 )
    Geoelectrochemical methods (CHIM) have been greatly changed after decades of development. Traditional low-efficiency technology has been replaced by extremely efficient methods. This paper reviews the history of CHIM's development and summarizes the progress made in recent years. Principles and methods of "independent power dipole CHIM technique" are introduced. Furthermore, questions related to method's application promotion are discussed and expected, such as commercialization of technical devices, technical system's standardization and mechanism of anomaly's formation.
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    The development and prospect of the spectral induced polarization method
    YANG Zhen-Wei, ZHENG Wei, LI Xiao-Bin, Wang Hua-Feng
    Geophysical and Geochemical Exploration. 2015, 39 (1): 22-28.   DOI: 10.11720/wtyht.2015.1.04
    Abstract   HTML   PDF (838KB) ( 708 )

    This paper mainly describes the research progress of spectral induced polarization method in the aspects of the system of instruments such as SIP-FUCHSII,V8, characteristics of the electrode arrangement and the methods of inversion. The data models include Cole-Cole model, CPA model, common Cole-Cole model and theoretical model SNP. The inversion methods include fromleast square inversion from 1D to 2D and even 3D. The applications of the spectral induced method in many fields in recent years are enumerated. In the end, the research direction of SIP is predicted: (1) 3D electromagnetic forward based on EM effect and IP effect simultaneously is the research focus and frontier in the future; (2) the detection of organic pollution used by SIP will become the new application field in the future.

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    Characteristics of soil geochemical anomalies and prospecting potential of Nanling area in Luoning Country, Henan Province
    DU Bao-Feng, CAI Zhi-Chao, WANG Chuan-Xian, ZENG Xiang, CHANG Yong-Wei, ZHANG Xin-Yuan
    Geophysical and Geochemical Exploration. 2015, 39 (1): 29-34.   DOI: 10.11720/wtyht.2015.1.05
    Abstract   HTML   PDF (2525KB) ( 656 )

    Located in the juncture between the Qinling orogenic belt and the southern margin of the North China Craton, the Nanling area in Luoning County of Henan Province belongs to the northern subzone of the Xiong'ershan lead-zinc-gold-silver polymetallic metallogenic belt. Based on 1:10 000 soil geochemical survey, the authors analyzed the element geochemical characteristics, single-element anomalies and geological environment for the occurrence of anomalies in the Nanling area, and finally delineated four comprehensive anomaly areas. Through verification, the authors found a lead-silver mineralization body in No.Ⅰanomaly area. In combination with an analysis of metallogenic geological environment, the authors hold that this area has promising prospecting potential for lead-zinc-silver resources and is a favorable area in search for epithermal filling metasomatic lead-zinc-silver polymetallic deposits. Continual work in the area is likely to get a breakthrough.

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    Gravity and magnetic anomalies and ore-prospecting orientation in Tunxi area,Anhui Province
    LIU Chun, REN Ming-Jun
    Geophysical and Geochemical Exploration. 2015, 39 (1): 35-40.   DOI: 10.11720/wtyht.2015.1.06
    Abstract   HTML   PDF (1149KB) ( 465 )

    Based on gravity and magnetic, geological and mineral resources data, this paper described characteristics of aeromagnetic and gravity anomalies in Tunxi area and, in combination with physical characters, analyzed geological factors responsible for the aeromagnetic and gravity anomalies and their reflections for geological structure and mineral resources. Gravity and magnetic anomalies are very clear in Tunxi area, which reflect the distribution regularity of basement, capping bed and intrusive rocks. It is held that Tunxi basin is a Paleozoic basement and hence the prospecting space can be considerably enlarged. It is also considered that Zhuxi type superlarge skarn tungsten-copper deposits are likely to be found in the Paleozoic basement of the red bed basin.

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    The role and effect of geophysical exploration in the ore-prospecting work of the Daijiazhuang Pb-Zn deposit in Dangchang County, Gansu Province
    JIN Hong-Wen, LI Bai-Xiang, MENG Zhen, HUA Tian-Yue
    Geophysical and Geochemical Exploration. 2015, 39 (1): 41-47.   DOI: 10.11720/wtyht.2015.1.07
    Abstract   HTML   PDF (6319KB) ( 714 )

    This paper puts forward some new opinions concerning the role and effect of geophysical exploration in different ore-prospecting stages of the integrated geophysical-geochemical exploration of the Daijiazhuang Pb-Zn deposit. The regional gravity and magnetic field characteristics were firstly used to determine the boundary between East Qinling and West Qinling and reveal the different geological-geochemical backgrounds and ore-controlling conditions; the IP measurement played the indirect ore-prospecting role in the reconnaissance and detailed investigation stages by means of detecting differences in physical characters of the objects; the rock-forming and ore-forming oxidation and reduction environment was investigated by means of high-precision magnetic measurement of the difference of weak anomalies; during the exploration and mining stage, the CSAMT was used to extend the known ore-bearing position outward, make locating and predicting and guide the mining work.

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    The effect of magnetotelluric (MT) sounding in oil-gas exploration in middle and upper Yangtze region
    Aisikaer, ZHANG Jian-Long, TAN Qin-Yin, Wushouaili, LIANG Sheng-Xian
    Geophysical and Geochemical Exploration. 2015, 39 (1): 48-53.   DOI: 10.11720/wtyht.2015.1.08
    Abstract   HTML   PDF (1446KB) ( 583 )

    Using magnetotelluric (MT) sounding technology, combined with the geological and physical characteristics of the survey area, the authors made a ground-underground comparative analysis of the fractures, folds and strata in middle and upper Yangtze region. The results show that the divisions of the structures are basically consistent with the distribution of surface structures. Integrated stratigraphic distribution, resistivity anomalies and geological conditions were used to explain the characteristics of the local structure. According to the local structural features and stratigraphic sequence, combined with the oil and gas geological analysis, the authors preliminarily hold that the electric characteristics of local structure in the western and central parts of the profile is clear, and that Cambrian and Sinian strata are buried under 4 000 m, the Silurian and Ordovician low resistivity beds are stably distributed, the capping beds are extensively developed, and the faults have relatively plugging properties, which are favorable for the preservation of Cambrian and Sinian oil and gas.

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    The application of relative amplitude compensation technology to lithologic reservoir exploration:A case study of lithologic gas reservoir in an oilfield of eastern China
    SU Shi-Long, HE Zheng-Hua, DAI Xiao-Yun, WANG Jiu-Shuan, ZHANG Hui, XIN Hua-Gang, LIU Yan-Na
    Geophysical and Geochemical Exploration. 2015, 39 (1): 54-59.   DOI: 10.11720/wtyht.2015.1.09
    Abstract   HTML   PDF (2431KB) ( 438 )

    Relative amplitude of seismic data processing research is a complicated system engineering.The authors analyzed the key to evaluating the deconvolution and relative amplitude compensation in practical seismic data processing flow,and pointed out that Yu wavelet statistical deconvolution has better predictive deconvolution in relative amplitude,and that residual amplitude compensation needs to use prestack elastic impedance or post-stack inversion results to verify relative amplitude of residual amplitude compensation.According to the principle of relative amplitude,the relative amplitude of seismic data are processed in the target area,and then pre-stack elastic parameters inversion is used to forecast the oil-gas possibility.The prediction result is consistent with the drilling result,thus demonstrating that the relative amplitude flow and methods have good application prospect.

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    The TEEM technology for quick identification of‘sweet spot’ of shale gas and its applications
    ZHOU Yin-Ming, LIU Xue-Jun, ZHANG Chun-He, ZHU Yong-Shan
    Geophysical and Geochemical Exploration. 2015, 39 (1): 60-63,83.   DOI: 10.11720/wtyht.2015.1.10
    Abstract   HTML   PDF (1030KB) ( 1045 )

    Based on a study of the electromagnetic characteristics of marine carbonate samples collected in southern China, the authors have reached the conclusion that shale beds typically show low resistivity on sections in marine carbonate areas, and this means that the shale beds can be identified with electromagnetic technique. In addition, measurement data of rock samples and core samples show that organic-rich shale beds have high polarization, which is closely related to high TOC, and this implies that we can identify‘sweet spot’ area of shale gas by using polarization anomaly. TFEM (Time and Frequency Electromagnetic) combines both time-domain sounding and frequency-domain sounding into a joint system, which induces target shale beds with a high-power transmitter. The method can help seismic technique to quickly identify target‘sweet spot’ of shale beds. The authors firstly analyze the physical properties of target shale beds, and then demonstrate the method for extracting electric and polarization anomalies aiming at the target beds. The combination of TFEM and seismic method makes the shale beds exploration more economical. This paper introduces this new and effective approach for quick identification of‘sweet spot’ and improving the success rate of shale gas exploration.

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    Examples of high resistivity anomaly containing fissure hot springs
    HUANG Zhuo-Xiong, YANG Xing-Mu
    Geophysical and Geochemical Exploration. 2015, 39 (1): 64-68.   DOI: 10.11720/wtyht.2015.1.11
    Abstract   HTML   PDF (956KB) ( 571 )

    United profile method and high-density electrical method were used for the groundwater geophysical exploration in Huangliu, Jiusuo and Yacheng surveyed areas near the Jiusuo-Lingshui faulted zone in Hainan Island. The authors found that water yield of the drill hole at the low-resistivity anomaly place of the Jiusuo surveyed area is low, whereas water yield of the drill hole at the lumpy high-resistivity anomaly place of the Huangliu surveyed is relatively large. In the Yacheng surveyed area, drilling at the high-resistivity place found bedrock fissure-type hot springs. It is preliminarily held that the low-resistivity place in the above surveyed area has low water yield due to rock fracturing, serious argillation and poor water quantity, whereas the water yield of the drill hole at the lumpy high-resistivity place is relatively high due to the facts that bedrock fissures are not filled with soil and mud and the hydraulic conductivity is fairly good.

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    Tectonic geochemistry of the central segment of the East Kunlun Mountains in Qinghai Province and its geological significance
    AN Guo-Ying
    Geophysical and Geochemical Exploration. 2015, 39 (1): 69-75.   DOI: 10.11720/wtyht.2015.1.12
    Abstract   HTML   PDF (1091KB) ( 439 )
    Geological survey in the middle part of East Kunlun Mountains is very insufficient. Based on geochemical information of 39 elements and oxides acquired by the scale 1:500,000 regional geochemical exploration, this paper deals with the geochemical characteristics of different tectonic units and major fault structures, combined with geological background. According to the parameter values of the elements,this paper sums up the elements distribution of different tectonic units and the basic law of earth crust evolution,and classifies groups of elements anomalies into seven elements geochemical anomaly zones in the region. Different fault structures have different geochemical characteristics, i.e., high-temperature ore-forming elements occur in Kunzhong faults whereas low-temperature metallogenic elements exist in Kunnan faults, so that the most important Au-Cu and Au-Sb polymetallic belts lie on both sides of Kunzhong faults and Kunnan faults zones. The mineralization in the different tectonic units shows different features from the north to the south,i.e., the elements evolved in order of Cu, Cd, Fe, Au, Pb, Zn, Ag, W, Sn-Au, As, Sb, Cu (Co), Pb, Zn-Au, Sb, As, Hg (Cu, W, Sn) southward.
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    Origin of oil and gas geochemical anomalies in the Qianjiadian sag
    RONG Fa-Zhun, TANG Yu-Ping, XU Ke-Wei, LU Li
    Geophysical and Geochemical Exploration. 2015, 39 (1): 76-83.   DOI: 10.11720/wtyht.2015.1.13
    Abstract   HTML   PDF (2722KB) ( 385 )

    According to an analysis of geochemical field in Qianjiadian sag, the authors revealed the intrinsic relationship between geochemical anomalies and the migration-enrichment of hydrocarbon. It is pointed out the future work should rely on the hydrocarbon and reservoir-forming conditions on the slope belt of the Hulihai depression to further determine and close the sand bodies in the favorable geochemical zone from Hulihai depression to east Xiboyingzi depression, with the near-source place as the major exploration target.

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    Aeromagnetic regional characteristics in southwest China
    LI Fu, WANG Yong-Hua, ZENG Qin-Qin, JIAO Yan-Jie
    Geophysical and Geochemical Exploration. 2015, 39 (1): 84-94.   DOI: 10.11720/wtyht.2015.1.14
    Abstract   HTML   PDF (3924KB) ( 547 )

    This article through to the southwest of aeromagnetic data, vertical guide and continuation of treatment, Southwest research aeromagnetic regional characteristics, determine the aerial magnetization in delay 20 km contour map as aeromagnetic regional anomaly in southwest China, the regional aeromagnetic anomalies in southwest divides the 13 partitions. Combined with geological, gravity, natural comprehensive inference and interpretation, seismic and remote sensing data could be divided into three first-order tectonic units in the southwest, 9 second-order tectonic units, 22 level 3 tectonic units; And focusing on six secondary tectonic units of geological and mineral and aeromagnetic anomaly characteristics, etc. Carried on the thorough analysis and research. Think high class-nujiang anomaly zone, the yarlung zangbo river and lake zones, sanjiang anomaly zone beaded magnetic anomaly are in good agreement with the properties of the metallogenic belt, prove that aeromagnetic anomalies is looking for a magnetic mineral effect is remarkable. Delay 10 km on the aeromagnetic anomalies and the quake's epicentre point comparison analysis research, proves the obvious, aeromagnetic reflect the characteristics of the deep fracture structure can obviously reflect the regional geological tectonic characteristics in southwest China.

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    The relationship between Xiatang warm spring and Checun-Lushan fault and the electrical sounding method as well as its application in exploration
    XIA Zhong-Guang
    Geophysical and Geochemical Exploration. 2015, 39 (1): 95-99.   DOI: 10.11720/wtyht.2015.1.15
    Abstract   HTML   PDF (1316KB) ( 417 )

    By means of electrical sounding and inversion interpretation with RGIS, the authors investigated the relationship between Xiatang warm spring and Checun-Lushan fault and found out the hydrogeological conditions within 1 500 m on both east and west sides of Xiatang warm spring. The results reveal that Xiatang warm spring is controlled by the EW-trending Checun-Lushan fault (F1), and also affected by the NE-trending F4 fault.. The former fault is the heat-conducting structure of level 1, and is also the major passage for upward convection of the deep heat source; the latter fault is the heat-conducting structure of level 2. Driven by the topography and the difference of hydraulic head pressure, the underground water migrates slowly along the fault zone from the west to the east. During the movement, the underground water is affected by the earth's internal heat-conduction and the NE-trending F4 fault and flows to the surface and is exposed as springs in the discharge area.

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    The effect of applying audio-frequency magnetotelluric method to the deep geological exploration: A case study of Wushan periphery in the Jiurui ore concentration area
    YAO Da-Wei, ZHU Wei, WANG Da-Yong, WANG Gang, ZHANG Zhen-Yu
    Geophysical and Geochemical Exploration. 2015, 39 (1): 100-103.   DOI: 10.11720/wtyht.2015.1.16
    Abstract   HTML   PDF (766KB) ( 582 )

    According to the geological background, metallogenic conditions and petrophysical characteristics in the surveyed area, three-dimensional geological mapping was studied by Audio-frequency Magnetotellurics Method (AMT). Based on AMT raw data processing and inversion interpretation, the authors inferred the underground resistivity differences of lithology and fracture structure within 2 km from the contact zone. Combined with the geological data and drilling results, the authors hold that the audio magnetotelluric method is good for detecting the underground geological body, clearly recognizing the marker bed of geoelectric layer and its hierarchical structure.

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    An analysis of applying the box wave survey technology to the Liupan Mountain loess tableland area
    PAN Jia-Zhi, XU Xiao-Kun, HE Jing-Guo, NING Peng-Peng, YE Chun-Xue
    Geophysical and Geochemical Exploration. 2015, 39 (1): 104-111,117.   DOI: 10.11720/wtyht.2015.1.17
    Abstract   HTML   PDF (6704KB) ( 606 )

    The Liupan Mountain basin is covered with thick loess,and is hence an area with complex surface bed and deep bed.Great thickness of loess and complex landform result in extremely well-developed interference waves in this area,which seriously affect the signal-to-noise ratio of the seismic data.In order to investigate the development characteristics of the interference waves in this area and conduct effective directed suppression,the authors,through an analysis of the application of the box wave survey technology in this area,put forward an effective way of box wave survey in combination with production,which can overcome the effect of static correlation on the data of box wave survey.In the light of the box wave survey data obtained from two landform conditions,the authors analyzed the variations of the interference field waves under the conditions of different landforms and surface beds,and found that the characteristics of interference waves that affect the shallow beds and the middle-deep beds are somewhat different.Through the analysis of the combined noise-suppressing effects,the authors put forward the combined receiving type for conducting directed noise-suppression suitable for exploration targets in different depths.The results achieved by the authors have improved the signal-to-noise ratio of the data collected from the target bed of the Liupan Mountain great thickness loess tableland area.

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    The denoising method for microseismic monitoring data in time-frequency domain
    DIAO Rui, SHAN Lian-Yu, SHANG Xin-Min, RUI Yong-Jun, ZHAO Cui-Xia
    Geophysical and Geochemical Exploration. 2015, 39 (1): 112-117.   DOI: 10.11720/wtyht.2015.1.18
    Abstract   HTML   PDF (2238KB) ( 526 )

    The microseismic monitoring data have low signal-to-noise ratio and contain lots of noise with different characteristics.The location accuracy of the microseismic event depends on the signal-to-noise ratio of microseismic monitoring data.In microseismic monitoring data processing,it is very important to improve the signal-to-noise ratio.The improved S transform,which has high time-frequency solution,is useful for microseismic monitoring data.Microseismic events can be better processed in time-frequency spectrum than in conventional Fourier transform.Based on the fine focus in time-frequency domain and flexible window function choice of improved S transform,the authors designed a 2D time variable time-frequency filter,which was used to process micro-seismic monitoring data.The combined signal and field micro-seismic monitoring data demonstrate the feasibility and efficiency of the method.

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    Effectiveness of magnetotelluric sounding inversion technique
    QIU Gen-Gen, ZHANG Xiao-Bo, PEI Fa-Gen, YUAN Yong-Zhen, BAI Da-Ming, ZHANG Peng-Hui
    Geophysical and Geochemical Exploration. 2015, 39 (1): 118-124.   DOI: 10.11720/wtyht.2015.1.19
    Abstract   HTML   PDF (1513KB) ( 785 )

    A simple three-dimensional model, a low-resistivity abnormal body and a high resistance abnormal body located in one-dimensional layered medium were designed in this paper. The authors used the "+" and "*" type observation profiles as the analog form to carry out the comparative experimental study of the effectiveness of MT 1D, 2D, 3D inversion. The authors employed adaptive regularization (ARIA) to perform 1D inversion, and adopted nonlinear conjugate gradient (NLCG) to conduct 2D inversion and REBOCC to carry out 3D inversion. The comparison of the different inversion results below the profile with the original model shows that 1D and 2D inversion can be reflected in the results of real model information, while 3D inversion of REBOCC tends to build a three-dimensional model of macroscopic electrical characteristics. In the 1D inversion results, as for the deep electrical structure, the inversion result shows that the TE polarization mode is better than TM polarization mode, and the combination mode of TE and TM has a medium result between the TE and TM. In the 2D inversion results, usually the TM polarization mode is better than TE polarization mode, and the inversion results of combination mode of TE with TM are almost equal with the TM polarization mode inversion results, or even better. In the 3D REBOCC inversion results, due to the influence of multiple solutions on inversion results, the 3D inversion of REBOCC tends to build a three-dimensional model of macroscopic electrical characteristics.

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    Pseudo-siesmic migration imaging based on numerical simulation results of a two-layered water-bearing mined out goaf model
    YAO Wei-Hua, LI Xiu, ZHAO Wei, YANG Zeng-Lin, QI Zhi-Peng, SUN Huai-Feng
    Geophysical and Geochemical Exploration. 2015, 39 (1): 125-131,140.   DOI: 10.11720/wtyht.2015.1.20
    Abstract   HTML   PDF (1580KB) ( 475 )

    The transient electromagnetic method is an effective exploration method for the coalfield mined-out area. The pseudo-seismic processing and interpreting of TEM have gradually become a hot research spot of EM exploration and made some breakthroughs. In this study. The authors employed the pseudo-seismic processing and interpreting method in coal mine goaf detection for higher detecting accuracy. With 3D finite difference time domain method of TEM, a model with two water bearing gobs was simulated. Pre-condition regularized conjugate gradient algorithm was used to realize stable transform from the diffusion field to the virtual wave field. And pulse compression was applied to virtual wave field. Finally, three-dimensional interpretation of the model was realized through the Kirchhoff integral equation downward migration imaging of the fictitious wave field data.

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    Three-dimensional simulation and test of source effects in CSAMT method
    WANG Gang, YANG Sheng, LEI Da, ZHU Wei, YAO Da-Wei
    Geophysical and Geochemical Exploration. 2015, 39 (1): 132-135.   DOI: 10.11720/wtyht.2015.1.21
    Abstract   HTML   PDF (730KB) ( 549 )

    Source effects have serious impact on the application effect of CSAMT. In order to analyze the effect of the source effects, the authors used three-dimensional integral equation numerical simulation method to simulate 3D anomalous body below the source, and then made a field test. Simulations and field tests have proved that, due to the different depths of the bedrocks, only the low band is affected, whereas the high band is almost unaffected, and that the low resistivity body can generate stronger source overprint effects, so the observational data are more remarkably impacted by the low resistivity body.

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    A comparison of advanced detection effect between the network parallel electrical method and the traditional method
    WU Chao-Fan, QIU Zhan-Lin, YANG Sheng-Lun, CHEN Yi-Xing
    Geophysical and Geochemical Exploration. 2015, 39 (1): 136-140.   DOI: 10.11720/wtyht.2015.1.22
    Abstract   HTML   PDF (2173KB) ( 528 )

    The network parallel electrical method is a direct current method with the "distributed parallel intelligent electrode potential difference signal acquisition method" as the core technological support. Its data acquisition simulates the style of seismic exploration. Different from the traditional electrical method in which every time of power supply can only pick out data of one measuring point, the network parallel electrical method can simultaneously obtain data of quite a few measuring points for every time of power supply, thus being a fully electric field observation. The authors used the two kinds of methods for the comparative study of advanced detection test in the Dawan coal mine and Wuping fluorite mine in Xinluo District of Longyan City, and conducted the actual tunnel drivage verification. The results show that the network parallel electrical method technology is better and more efficient than the traditional method.

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    Log-ratio transformation and PLS methods for identifying integrated geochemical anomalies: A case study of lead-zinc mineralization in northwestern Hunan
    WANG Kun, XIAO Ke-Yan, CONG Yuan
    Geophysical and Geochemical Exploration. 2015, 39 (1): 141-148.   DOI: 10.11720/wtyht.2015.1.23
    Abstract   HTML   PDF (2915KB) ( 642 )

    As lead-zinc deposits in northwestern Hunan are controlled by strata, the authors chose statistical regularities of constant elements in the ore-bearing layer as the basis of integrated geochemical anomaly extraction and used a stream sediment geochemical dataset. Firstly, three main forms of log-ratio transformation were used to explore the effects of the constant elements data closure problem. On such a basis, the PLS method was employed to study the integrated geochemical anomalies. The results show that data transformed by ilr method have obvious symmetrical statistical features and are much closer to the normal distribution. In contrast with PCA and FA, the integrated geochemical anomalies extracted by PLS method are generally more consistent with such geochemical features of lead-zinc mineralization in the study area as the known ore deposits and the fault distribution, and the results can be explained easier in geological field.

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    The tentative application of the geoelectro-chemical extraction method to the deep prospecting: A case study of the Hucun copper-molybdenum deposit in Anhui Province
    ZHI Chao, XIANG Wu, ZENG Jian-Nian, Xie Shu-Yun, YU Sang, ZHENG Qin-Yuan, LU Shun-Fu, WAN Xiang
    Geophysical and Geochemical Exploration. 2015, 39 (1): 149-155.   DOI: 10.11720/wtyht.2015.1.24
    Abstract   HTML   PDF (3546KB) ( 412 )

    The feasibility study of the geoelectric extraction method was conducted in the Hucun copper deposit, Anhui Province. The result shows that the geoelectro-chemical extraction method can improve anomaly contrast and hence is very suitable for detailed exploration work of weak regional geochemical anomalies. In particular, As, Sb, Se, Ag and Pb with a high anomaly contrast and a wide abnormal range are somewhat valuable for deep mineral exploration. Ba and Zn also have some indication significance. In addition, the authors measured the pH and κs anomalies which could effectively distinguish geoelectric extraction anomalies caused by shallow mineralization. According to the field test, the method is not suitable for thin soil bedrock outcrop area. At the same time, taking into account the considerable workload, the authors hold that the electrochemical measurements can be used to fine deep geochemical prospecting work.

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    Triangular grid-based rapid mapping of scattered data
    LI Xiao-Dong, JIN Sheng, WANG Yang-Ling, ZHANG Jia-Hong, CHENG Li-Hui
    Geophysical and Geochemical Exploration. 2015, 39 (1): 156-160.   DOI: 10.11720/wtyht.2015.1.25
    Abstract   HTML   PDF (1227KB) ( 843 )
    Conventional contour mapping performs interpolation based on a rectangular grid. A linear interpolation method is presented in this paper based on triangular mesh. Triangular mesh can better approximate the boundary of scattered data and the morphology of geophysical field, which makes the contour maps smoother. By searching boundary, triangulated mesh, linear interpolation, search contours, Bezier curves and smooth contours, five steps can be carried out quickly for any scattered data mapping. The actual data mapping results show that the interpolation method is good in that no data extrapolation is needed, the contour map obtained directly reflect the spatial location of scattered data, and the mapping is speeded. The method can therefore greatly improve the efficiency of the actual work.
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    The application of GPU accelerated multi-step reverse time migration to the Dongpu oilfield
    ZHANG Hui, CAI Qi-Xin, QIN Guang-Sheng, GAO Ai-Rong, LIN Yu-Ying
    Geophysical and Geochemical Exploration. 2015, 39 (1): 161-165.   DOI: 10.11720/wtyht.2015.1.26
    Abstract   HTML   PDF (1954KB) ( 546 )

    In order to solve complicated faults imaging problem of the Dongpu oilfield,the authors utilized multi-step reverse time migration method and realized GPU accelerate parallel algorithm for overcoming the low compute efficiency disadvantage of RTM.The GPU accelerated multi-step reverse time migration method was successfully applied to complicated faults imaging processing.The RTM imaging result of Qianliyuan 3D data proved the technological advantage of RTM for complicated small faults imaging and Lanliao dip-angle faults imaging.Migration efficiency analyses demonstrate that RTM based on GPU accelerate algorithm can effectively improve the computational efficiency by 75 times.

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    The folds in seismic reflection exploration for Xi'an ground fissure investigation
    CHENG Yao, SUI Cheng-Xing, YANG Long-Wei, JU Zhao-Hui, LI Zhong-Sheng
    Geophysical and Geochemical Exploration. 2015, 39 (1): 166-171.   DOI: 10.11720/wtyht.2015.1.27
    Abstract   HTML   PDF (4992KB) ( 399 )

    In the investigation of Xi'an ground fissures,the higher the fold of seismic reflection exploration,the higher the signal-to-noise ratio profile is obtained.Nevertheless,it also increases the difficulty of field work and raises the exploration cost.In order to study the effect of different folds in Xi'an ground fissure seismic exploration,the authors chose seismic reflection data in three different sites as examples for analysis.These seismic data were processed in different stacking folds via the method for reducing shot points.The stacking profiles with different folds were compared with each other to extract exploration effect in combination with validated borehole information.It is believed that,if original field records have high signal-to-noise ratios,12 reflection folds can significantly determine the ground fissure anomalies,with 6 reflection folds being the minimum.

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    Salinization characteristics of soil profile in coastal areas of Tianjin and its affecting factors
    WANG Wei-Xing, LI Gong-Ke, HOU Jia-Yu, LIU Yong-Tao
    Geophysical and Geochemical Exploration. 2015, 39 (1): 172-179.   DOI: 10.11720/wtyht.2015.1.28
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    Soil salinization is a major environmental risk caused by natural or human activities, and it has an important adverse effect on the industrial and agricultural production activities of mankind. The authors conducted the study of the layout of the 6 representative soil salinization profiles in the coastal areas of Tianjin, and chose 4 profiles as the monitoring sections for the two-year monthly sampling and monitoring. Studies show that the soil salinity profiles are of the bottom accumulation types in coastal area, except for BHY6 soil profile which shows the balance of soil profile type with years of farming. The cations are mainly Na+, and the anions are mainly Cl- or Cl- and HCO3-. From the lower soil profile to the bottom of the shallow groundwater level, the proportions of Na+, Cl- ions in soil possess the absolute superiority in the shallow groundwater with significantly higher salinity (up to saline degree), and this shows the basic characteristics of coastal solonchak. Climatic factors, salinity and depth of the shallow groundwater and the vegetation in surface soil are important factors affecting soil salinization of coastal areas. The surface soil shows the features of salt accumulation in spring, desalination in summer, and slow salt accumulation in autumn and winter. The shallow groundwater mineralization degree is higher, and the shallower the buried depth, the higher the soil salt content. The fruit trees and long cultivated land can reduce soil salt accumulation effectively and lower the degree of soil salinization of soil in coastal areas, which is crucial for the protection and improvement of soil.

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    The distribution of the surface soil organic carbon storage and density in western Chongqing
    BAO Li-Ran, YAN Ming-Shu, JIA Zhong-Min, GONG Yuan-Yuan
    Geophysical and Geochemical Exploration. 2015, 39 (1): 180-185.   DOI: 10.11720/wtyht.2015.1.29
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    Based on the soil data obtained by multi-purpose regional geochemical survey, the authors estimated the surface soil organic carbon storage and organic carbon density in western Chongqing. The results show that the surface soil organic carbon storage is 41 038 589 t, with organic carbon average density of 2 929 t·km-2. As for geomorphological types, the soils of low maintains (2 984 t·km-2) and middle maintains (2 986 t·km-2) have higher organic carbon density, the density of hills soil is the lowest, and the maintainous soil has most abundant organic carbon storage. In different soil types, the organic carbon density of limestone soil is the highest (5 043 t·km-2), followed by yellow soil (3 756 t·km-2), the organic carbon density of purple soil is the lowest (2 329 t·km-2), and the organic carbon storage of purple soil is the highest. Regarding the land use, the organic carbon density of forest land is the highest (4 071 t·km-2), the cultivated land is at the middle level (2 752 t·km-2), the resident and building soil is the lowest (2 416 t·km-2), and the organic carbon storage of the cultivated land is the highest. A comparison with the data of the Second Soil General Survey shows that the surface soil organic carbon storage and organic carbon density have been reduced and, as‘carbon source’, the surface soil has released organic carbon to the air. Especially the soil in Nanchuan and Jiangjin has decreased by 56.7% and 45.1% respectively.

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    The regularization inversion of induced polarization relaxation time spectrum of agrillaceous sand
    TONG Mao-Song
    Geophysical and Geochemical Exploration. 2015, 39 (1): 186-191.   DOI: 10.11720/wtyht.2015.1.30
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    The time-domain induced polarization (IP) decay curve is a linear superposition of IP signal from individual pores. It can be transformed to relaxation time spectrum related to the pore structure and can be used to estimate the permeability of the argillaceous sand. So the IP logging is a useful tool for reservoir characterizing. The singular value decomposition (SVD) method can be used to extract the relaxation time spectra from the decay data with high signal-to-noise ratio (SNR). This method is unstable and invalid for the practical downhole use because of the noisy decay data. In this study, a method of regularization was applied to extracting continuous IP relaxation time spectra from simulated and real decay data. Influence of the regularization factor, SNR and relaxation time arrangement on the spectra was also discussed. Firstly, for the simulated decay data with noise, the spectra become smoother with increasing regularization factor. There is an optimal value which can be used to get the most reasonable spectrum. The optimal factor decreases linearly with increasing SNR on a log-log scale. This relationship can be used to predict the optimal factor from a known SNR. Secondly, the influence of relaxation time arrangement on the spectra shows that the suitable relaxation distribution point ranges from 32 to 64. Finally, the developed algorithm and the prediction of the optimal factor are very suitable for the inversion of the spectra of the real data.

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    Software and hardware design of analog output for the data of magnetic diurnal variation
    WU Cheng-Ping, YU Chang-Chun
    Geophysical and Geochemical Exploration. 2015, 39 (1): 192-195.   DOI: 10.11720/wtyht.2015.1.31
    Abstract   HTML   PDF (882KB) ( 363 )

    According to the features of analog record for magnetic diurnal variation, the authors implemented the function of printing the magnetic diurnal variation by using D/A conversion chip. With D/A conversion chip as the main part, the case and connector were designed. The software is compiled by Visual Basic, and its function and operation were described. The test of measured data and the comparison with the curve from actual measurement indicate that there exists a high level of consistency between them, and it is feasible to copy analog record of magnetic diurnal variation by using the software and hardware from this paper. The technique is conducive to saving and sharing the analog record of magnetic diurnal variation and promoting the unattended work of magnetic diurnal variation measurement.

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    Reverse-time migration for TI medium based on vector wavefield separation
    REN Li-Juan, LI Zhen-Chun, WANG Yan-Guang, LIU Xing-Da, SUN Xiao-Dong
    Geophysical and Geochemical Exploration. 2015, 39 (1): 196-202.   DOI: 10.11720/wtyht.2015.1.32
    Abstract   HTML   PDF (1522KB) ( 648 )
    Two-step separation was conducted for anisotropy vector wavefield.The first step is to make the anisotropic elastic wave equation in the polarization direction of the projection isotropic so that it has clear and intuitive kinematic and dynamic characteristics;the second step is to calculate anisotropic medium propagator wavefield separation waveform correction based on the correction of the projected direction of the wavefield in the isotropic direction back to the anisotropic direction, and ultimately the anisotropic wavefield separation can be achieved.First of all,the test of VTI media proves its feasibility.In addition,the authors put forward the surface data decomposition,namely,data decomposition is conducted for collected multicomponent seismic data before the migration imaging.In order to get the pure qP wave,qSH wave and qSV wave data the authors conducted the surface data input control to obtain the satisfactory imaging results of components and make imaging decomposition of the surface data performed in a controlled process,thus reducing unnecessary computation.The authors conducted decomposition of Hess forward modeling shot record data and reverse-time migration imaging.
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    Stochastic inversion of elastic impedance based on Metropolis sampling algorithm
    SUN Rui-Ying, YIN Xing-Yao, WANG Bao-Li, ZHANG Guang-Zhi
    Geophysical and Geochemical Exploration. 2015, 39 (1): 203-210.   DOI: 10.11720/wtyht.2015.1.33
    Abstract   HTML   PDF (1981KB) ( 596 )
    Stochastic inversion of elastic impedance based on Metropolis sampling algorithm is a Monte Carlo based strategy for non-linear inversion,which can effectively integrate the high-frequency information of well-logging data and have a higher resolution.This method is formulated in the Bayesian framework.Firstly,the priori information can be obtained through Fast Fourier Transform-Moving Average (FFT-MA) and Gradual Deformation Method (GDM).Then Metropolis algorithm is employed so as to obtain an exhaustive characterization of the posteriori probability density.FFT-MA is a kind of efficient simulation method.Combined with GDM,it can constantly modify the reservoir model and keep the spatial structure unchanged until it matches the observed seismic data.According to the numerical calculations,it can be concluded that FFT-MA simulation can reduce the time consumption.Combined with GDM updating algorithm,the inversion results can converge rapidly,and the final results match the model well and have a higher resolution.In addition,this method adopts two-step method to invert elastic parameters,so it improves the computational efficiency to some extent.
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    The calculation of the instantaneous frequency using the continuous phase in dynamic matching pursuit algorithm
    LIU Han-Qing, ZHANG Fan-Chang, DAI Rong-Huo, YIN Xing-Yao
    Geophysical and Geochemical Exploration. 2015, 39 (1): 211-216.   DOI: 10.11720/wtyht.2015.1.34
    Abstract   HTML   PDF (1810KB) ( 479 )
    The instantaneous characteristics of signals,as the priori information,have been introduced into the signal decomposition which can reduce the scanning range of the atomic library and improve the efficiency of the dynamic matching pursuit algorithm.However,when we use the instantaneous phase to obtain the instantaneous frequency,there will be negative frequency without physical meaning and the negative instantaneous frequency can't be applied to matching pursuit.As far as we know,there is no effective solution to overcome the negative instantaneous frequency in matching pursuit. In view of such a situation,the authors,through studying the difference between the principal phase and the unwrapping phase,propose a method to obtain the instantaneous frequency by introducing the continuous phase.Then the formula of calculating continuous phase can be deduced.In the numerical data tests,the authors present the trend graphs that reflect the changes of the three different phases.Finally,the comparison of the instantaneous frequencies obtained by the three phases proves that the instantaneous frequency obtained by the continuous phase avoids the negative anomalies,and hence it is a good choice for matching pursuit algorithm and can be used directly.
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