全局优化的Fourier有限差分偏移方法研究

Seismic exploration is the main method of seeking oil and gas. With the development of seismic exploration, the target becomes more and more complex, which leads to a higher demand for the accuracy and efficiency in seismic exploration. Fourier finite-difference (FFD) method is one of the most valuable methods in complex structure exploration, which has obtained good effect. However, in complex media with wider angles, the effect of FFD method is not satisfactory. Based on the FFD operator, we extend the two coefficients to be optimized to four coefficients, then optimize them globally using simulated annealing algorithm. Our optimization method select the solution of one-way wave equation as the objective function. Except the velocity contrast, we consider the effects of both frequency and depth interval. The proposed method can improve the angle of FFD method without additional computation time, which can reach 75° in complex media with large lateral velocity contrasts and wider propagation angles. In this thesis, combinating the FFD method and alternative-direction-implicit plus interpolation(ADIPI） method, we obtain 3D FFD with higher accuracy. On the premise of keeping the efficiency of the FFD method, this method not only removes the azimuthal anisotropy but also optimizes the FFD mehod, which is helpful to 3D seismic exploration. We use the multi-parameter global optimization method to optimize the high order term of FFD method. Using lower-order equation to obtain the approximation effect of higher-order equation, not only decreases the computational cost result from higher-order term, but also obviously improves the accuracy of FFD method. We compare the FFD, SAFFD（multi-parameter simulated annealing globally optimized FFD）, PFFD, phase-shift method(PS）, globally optimized FFD （GOFFD）, and higher-order term optimized FFD method. The theoretical analyses and the impulse responses demonstrate that higher-order term optimized FFD method significantly extends the accurate propagation angle of the FFD method, which is useful to complex media with wider propagation angles.

复杂裂隙岩体统计断裂本构关系与变形参数研究

Rock mass is widely recognized as a kind of geologic body which consists of rock blocks and discontinuities. The deformation and failure of rock mass is not only determined by rock block，but also by discontinuity which is virtually more important. Mutual cutting and combination of discontinuities controlled mechanical property of rock mass. The complex cutting of discontinuities determine the intense anisotropy on mechanical property of rock mass，especially under the effect of ground stress. Engineering practice has show that the brittle failure of hard rock always occurs when its working stress is far lower than the yield strength and compressive strength，the failure always directly related to the fracture propagation of discontinuities. Fracture propagation of discontinuities is the virtue of hard rock’s failure. We can research the rock mass discontinuous mechanical properties precisely by the methods of statistical analysis of discontinuities and Fracture Mechanics. According to Superposition Principle in Fracture Mechanics，A Problem or C Problem could be chosen to research. Problem A mainly calculates the crack-tip stress field and displacement field on internal discontinuities by numerical method. Problem C calculate the crack-tip stress field and displacement field under the assumption of that the mainly rock mass stress field has been known. So the Problem C avoid the complex mutual interference of stress fields of discontinuities，which is called crack system problem in Fracture Mechanics. To solve Problem C, field test on stress field in the rock mass is needed. The linear Superposition of discontinuities strain energies are Scientific and Rational. The difference of Fracture Mechanics between rock mass and other materials can mostly expression as：other materials Fracture Mechanics mostly face the problem A，and can’t avoid multi-crack puzzle, while the Rock mass Fracture Mechanics answer to the Problem C. Problem C can avoid multi-discontinuities mutual interference puzzle via the ground stress test. On the basis of Problem C, Fracture Mechanics could be used conveniently in rock mass. The rock mass statistics fracture constitutive relations, which introduced in this article, are based on the Problem C and the Discontinuity Strain Energy linear superposition. This constitutive relation has several merits: first, it is physical constitutive relation rather than empirical; second, it is very fit to describe the rock mass anisotropy properties; third, it elaborates the exogenous factors such as ground stress. The rock mass statistics fracture constitutive relation is the available approach to answer to the physical, anisotropic and ground stress impacted rock mass problems. This article stand on the foundation of predecessor’s statistics fractures constitutive relation, and improved the discontinuity distributive function. This article had derived the limitation of negative exponential distribution in the course of regression analysis, and advocated to using the two parameter negative exponential distribution for instead. In order to solve the problems of two-dimension stability on engineering key cross-sectional view in rock mass, this article derived the rock mass planar flexibility tensor, and established rock mass two-dimension penetrate statistics fracture constitutive relation on the basis of penetrate fracture mechanics. Based on the crack tip plasticity research production of penetrate fracture, for example the Irwin plasticity equifinality crack, this article established the way to deal with the discontinuity stress singularity and plastic yielding problem at discontinuity tip. The research on deformation parameters is always the high light region of rock mass mechanics field. After the dam foundation excavation of XiaoWan hydroelectric power station, dam foundation rock mass upgrowthed a great deal of unload cracks, rock mass mechanical property gotten intricacy and strong anisotropy. The dam foundation rock mass mostly upgrowthed three group discontinuities： the decantation discontinuity, the steep pitch discontinuity, and the schistosity plane. Most of the discontinuities have got partial unload looseness. In accordance with ground stress field data, the dam foundation stress field greatly non-uniform, which felled under the great impaction of tectonic stress field, self-weight stress field, excavation geometric boundary condition, and excavation, unload. The discontinuity complexity and stress field heterogeneity, created the rock mass mechanical property of dam foundation intricacy and levity. The research on the rock mass mechanics, if not take every respected influencing factor into consideration as best as we can, major errors likely to be created. This article calculated the rock mass elastic modulus that after Xiao Wan hydroelectric power station dam foundation gutter excavation finished. The calculation region covered possession monolith of Xiao Wan concrete double-curvature arch dam. Different monolith were adopted the penetrate fracture statistics constitutive relation or bury fracture statistics constitutive relation selectively. Statistics fracture constitutive relation is fit for the intensity anisotropy and heterogeneity rock mass of Xiao Wan hydroelectric power station dam foundation. This article had contrastive analysis the statistics fracture constitutive relation result with the inclined plane load test actual measurement elastic modulus and RMR method estimated elastic modulus, and find that the three methods elastic modulus have got greatly comparability. So, the statistics fracture constitutive relations are qualified for trust. Generally speaking，this article had finished following works based on predecessors job: “Argumentation the C Problems of superposition principle in Fracture Mechanics, establish two-dimension penetrate statistics fracture constitutive relation of rock mass, argue the negative exponential distribution limitation and improve it, improve of the three-dimension berry statistics fracture constitutive relation of rock mass, discontinuity-tip plastic zone isoeffect calculation, calculate the rock mass elastic modulus on two-dimension cross-sectional view”. The whole research clue of this article inherited from the “statistics rock mass mechanics” of Wu Faquan（1992）.

三维非均匀各向异性介质中的纵波走时反演研究

Many observations show that seismic anisotropy is very common in the crust and upper mantle of the Earth. Seismic anisotropy can provide some clue about the changing and transporting process inside the earth. in recent years, abundant earthquake travel time data are accumulated, computers become more powerful, and these make the inversion of earthquake travel time data practical. In this thesis we studied the theory of elastic wave in anisotropic media, some formule for travel time inversion were derived. We present an iterative procedure to determine 21 elastic parameters from qP wave travel times. No a priori assumptions about heterogeneity and anisotropy of the model are made. The procedure is suitable for the case when we know nothing about the symmetry of anisotropy of the media, as well as for the case of earthquake travel time inversion which may contain various symmetry of anisotropy. The procedure is tested with a synthetic multiple-source offset VSP experiment. The results proved that the formulae are correct, and the procedure is practical. The results and the related theory indicate that the anisotropic inversion needs more rays than isotropic case. For a 2-D weak anisotropic (WA) medium, we need at least 5 rays in different directions to retrieve the elastic parameters on one grid point, and for a 3-D WA medium we need at least 15 rays in different directions to retrieve the elastic parameters on one grid point. The results also indicate that the starting background velocity has no influence on the final results, at least for the model we specified. Our results also show that insufficient illumination coverage will slow down the convergence rate, and make the results more sensitive to noise. We apply the procedure to a set of field travel time data. The data is from an artificial seismic observation. This observation is for locating micro-seismic events around a tunnel, its purpose is to find out if the digging process and the stress condition around the tunnel can generate micro-cracks. The size of this area is around 100m. The anisotropy derived from qP travel times is the same as the anisotropy showed by apparent velocities, and is also consistent with the anisotropy derived from S-wave splitting phenomena.

沾化凹陷火成岩油气藏形成条件和分布规律研究

As a kind of special lithologic ones, Igneous rock oil and gas pool is more and more paid attention, and it has different forming condition and distribution from conventional ones, such as various terrane distribution types, serious reservoir anisotropy, complicated hydrocarbon-bearing, so there is not successful experience to follow for exploration and development of this complex subtle oil and gas pool at present. For an example of Igneous oil and gas pool of Luo151 area in Zhanhua seg, Eastern China, this article study the difficult problem, including petrologic nd lithofacies analysis, Origin, invasion age and times of Igneous rock, reservoir anisotropy, Geological Modeling, Igneous reservoir synthesis evaluation. forming condition and distribution are studied synthetically, and an integrated method to predict igneous rock oil and gas pool is formed, which is evaluated by using development data. The Igneous rock is mainly diabase construction in Luo151 area of Zhanhua Sag, and petrologic types include carbonaceous slate, hornfels, and diabases. Based on analyzing synthetically petrologic component, texture and construct, 4 lithofacies zones, such as carbonaceous slate subfacies, hornfels subfacies containing cordierite and grammite, border subfacies and central subfacies, are divided in the diabase and wall rock. By studying on isotopic chronology, terrane configuration and imaging logging data, the diabase intrusion in Zhanhua Sag is formed by tholeiite magma emplacing in Shahejie formation stratum on the rift tension background Lower Tertiary in North China. The diabase intrusion of Luo151 is composed possibly of three periods magma emplacement. There is serious anisotropy in the diabase reservoirs of Luo151 in Zhanhua Sag. Fracture is primary reservoir space, which dominated by tensile fracture in high obliquity, and the fracture zones are mainly developed round joint belt of igneous rock and wall rock and position of terrane thickness changing rapidly. The generation materials of the reservoirs in Luo151 igneous oil pools consist of Intergranular micropore hornfels, condensate blowhole-solution void diabase condensate edge, the edge and center of the condensate seam diabase, of which are divided into horizontal, vertical and reticulated cracks according fracture occurrence. Based on the above research, a conceptual model of igneous rock reservoir is generated, which is vertically divided into 4 belts and horizontally 3 areas. It is built for the first time that classification evaluation pattern of igneous rock reservoir in this area, and 3 key wells are evaluated. The diabase construction is divided into grammite hornfels micropore type and diabase porous-fracture type reservoirs. The heavy mudstone layers in Third Member of Shahejie formation (Es3) provide favorable hydrocarbon source rock and cap formation, diabase and hornfels belts serve as reservoirs, faults and microcracks in the wall rocks as type pathways for oil and gas migration. The time of diabase invasion was about in the later deposition period of Dongying Formation and the middle of that of Guantao Formation, the oil generated from oil source rock of Es3 in the period of the Minghuazhen formation and is earlier more than the period of diabase oil trap and porous space forming. Based on geological and seismic data, the horizon of igneous rocks is demarcated accurately by using VSP and synthetic seismogram, and the shape distribution and continuity of igneous rocks are determined by using cross-hole seismic technology. The reservoir capability is predicted by using logging constraining inversion and neural network technology. An integrated method to predict igneous rock oil and gas pool is formed. The study is appraised by using development data. The result show the reservoir conceptual model can guide the exploration and development of oil pool, and the integrated method yielded marked results in the production.

华南地壳岩石弹性和变形性质的高温高压实验研究

The South continent of China lies to southeast of Eurasia block. It is an active area from the view of crust growth and continent spread and is a transition zone between continental crust and oceanic crust. The compressional wave velocities and anisotropies of typical crustal metamorphic rocks were determined at high temperature (up to 1000 ℃) and high pressure(up to 800MPa). The experimental results show that the velocities generally increase with pressure, and is unaffected by temperature up to around 550 ℃. But the velocities of all experimental samples start to drop above a temperature point. For an example, this greatly reduce the speed of wave propagation in amphibolite and serpentinite above 760 ℃ and above 550 ℃ respectively, which may be due to dehydrate of amphibole and serpentine. P-wave anisotropy coefficients of those rocks range from 2% to 10% at 800MPa and 500 ℃. The anisotropies decrease with increasing pressure at room temperature, but hardly change as function of temperature at constant 800MPa or 600MPa pressure. The average velocity of the six crustal rocks is 6.28km/s under the condition of 800MPa and 550 ℃, which is consistent with the result of deep seismic sounding data. Based on this experimental result, we deduce there may exist a lot of felsic granulites and amphibolites at the depth of 15-25km underground. With increasing temperature and pressure, the deformation behavior of the rocks undergoes from localized brittle fracture, semi-brittle deformation (cataclastic flow or semi-brittle faulting, semi-brittle flow) to homogeneous crystal-plastic flow. This transition is associated with mechanical behavior and micro-mechanism. It is very important to understanding earthquake source mechanics, the strength of the lithosphere and the style of deformation. The experiments were conducted at temperature of 600-1000 ℃, confining pressure of 500MPa, and stain rates of 10~(-4)-10~(-6) S~(-1). For fine-grained natural amphibolite, the results of experiments show that brittle faulting is major failure mode at temperature <600 ℃, but crystal-plastic deformation is dominate at temperature >800 ℃, and there is a transition with increasing temperature from sembrittle faulting to cataclastic flow and sembrittle flow at temperature of 670-750 ℃. For medium-grained natural Felsic granulite, the results of experiments show that brittle faulting is major failure mode at temperature <500 ℃, but crystal-plastic deformation is dominate at temperature >700 ℃, and there is a transition with increasing temperature from semibrittle faulting to cataclastic flow and sembrittle flow at temperature of 500-600 ℃.

陇西盆地晚第三纪风尘沉积的地层学研究

In Asia, the significant environment changes in Cenozoic include: uplift of Himalayas and Tibetan Plateau, formation Asian monsoon system, Aridification in Central Asia. One of major advances in recent studies of eolian deposit on the Loess Plateau is the verification of the eolian origin for the Late Tertiary Hipparion Red-Earth (also called red-Clay) underlying the Quaternary loess. Thus, the Late Tertiary eolian deposit, which has been proven a nearly continuous terrestrial record and sensitive to climate change, provides us an important archive to understand these above Cenozoic environment events. The deposit in eastern Loess Plateau has been extensively studied, while the property and age of deposit underlying the Quaternary loess in western plateau remains unclear. In this paper, detail investigations were made on the Sedimentology, geochemistry of Longxi section, a typical section in western Loess Plateau, to address its origin, and on micromammalian fossils and magnetostratigraphy to address its age. The main conclusions are presented as following: 1. The sedimentological and geochemical properties in Longxi section are highly similar to typical Quaternary eolian deposit in Loess Plateau. Nearly 100 paleosols are recognized in the field, and the grain size are very fine with the median grain size centered at 4～7μm. There is a good agreement of both major and trace element compositions between Longxi deposit and the Quaternary Loess. The REE distribution patterns of Longxi deposit and the Quaternary loess are remarkably similar in shape, with enrichment LREE and fairly flat HREE profiles and clear negative Eu anomaly. The mangnetic minerals in Longxi deposit are mainly magnetite, hematite and maghematite, which are similar to those of the Hipparion Red-Earth and Quaternary Loess. The major difference among them is that the samples from Longxi section contain more hematite. The characteristics of anisotropy of magnetic susceptibility (AMS) in Longxi deposit is highly consistent with that of Quaternary loess, while values of the major AMS parameters, e.g. anisotropy degree, magnetic foliation and lineation, are significantly lower than those of fluvial and lake deposits. These evidences indicate an eolian origin for the sediment. 2. An investigation of micromammalian fossils was firstly carried out for determining the approximate age of the sequence because of lack of materials for accurate isotope dating. Three fossil assemblages were obtained which indicate a chronological range from the Middle Miocene to Late Miocene. The magnetostratigraphical study suggests that it is a near continuous terrestrial record for the period from 13.23 to 6.23 MaB.P. The obtained chronology is highly consistent with fossils assemblages. This section is the oldest eolian deposit presently known in Loess Plateau. 3. The magnetic susceptibly value is high in paleosols than in surrounded weak-weathered layers, which suggests that it may be a climate index on orbital time scale. While it cannot be used as a proxy to address the long-term, change of climate on tectonic time scale, as content of the magnetic minerals is highly variable in different parts of the section. 4. The appearance of Middle Miocene eolian deposit in the Loess Plateau marks the strengthening of aridification of Central Asia. The high degree of similarity between the geochemical properties of Longxi eolian deposit, Hipparion Red-Earth and Quaternary loess a suggests that a rather similar source provenance. The dust accumulation rate (DAR) of Longxi section, which is widely used as a proxy to document the aridity in source areas in marine and terrestrial record studies, recorded the aridity condition in northwestern China over a period from Middle Miocene to Late Miocene. The DAR of the section shows that the continent aridity remains moderate and relative stable over that period.

泥岩裂缝储层地震识别的理论和方法

During the exploration of fractured reservoirs, worldwide difficult problems will be encountered: how to locate the fractured zones, how to quantitatively determine the azimuth, density, and distribution of the fractures, and how to compute the permeability and porosity of the fractures. In an endeavor to solve these problems, the fractured shale reservoir in SiKou area of ShengLi oil field was chosen as a study area. A study of seismic predictive theory and methods for solving problems encountered in fractured reservoir exploration are examined herein. Building on widely used current fractured reservoir exploration techniques, new seismic theories and methods focusing on wave propagation principles in anisotropic medium are proposed. Additionally, integrated new seismic data acquisition and processing methods are proposed. Based on research and application of RVA and WA methods from earlier research, a new method of acoustic impedance varying with azimuth (IPVA) creatively is put forth. Lastly combining drilling data, well log data, and geologic data, an integrated seismic predictive method for cracked reservoir bed was formed. A summary of the six parts of research work of this paper is outlined below. In part one, conventional geologic and geophysical prediction methods etc. for cracked reservoir exploration are examined, and the weaknesses of these approaches discussed. In part two, seismic wave propagation principles in cracked reservoirs are studied. The wave equation of seismic velocity and attenuation factor in three kinds of fracture mediums is induced, and the azimuth anisotropy of velocity and attenuation in fracture mediums is determined. In part three, building on the research and application of AVA and WA methods by a former researcher, a new method of acoustic impedance creatively varying with azimuth (IPVA) is introduced. A practical software package utilizing this technique is also introduced. In part four, Base on previously discussed theory, first a large full azimuth 3d seismic data (70km~2) was designed and acquired. Next, the volume was processed with conventional processing sequence. Then AVA, WA, and IPVA processing was applied, and finally the azimuth and density of the fractures were quantitatively determined by an integrated method. Predictions were supported by well data that indicate the approach is highly reliable. in part five, geological conditions contributing to cracked reservoir bed formation are analyzed in the LuoJia area resulting in the discovery that the main fractured zones are related to fault distribution in the basin, that also control the accumulation of the oil and gas, the generation mechanisms and types of fractured shale reservoirs are studied. Lastly, by using full 3D seismic attributes, azimuth and density of cracked reservoir zones are successfully quantitative predicted. Using an integrated approach that incorporates seismic, geologic and well log data, the best two fractured oil prospects in LouJia area are proposed. These results herein represent a break through in seismic technology, integrated seismic predictive theory, and production technology for fractured reservoirs. The approach fills a void that can be applied both inside China, and internationally. Importantly, this technique opens a new exploration play in the ShengLi oil field that while difficult has substantial potential. Properly applied, this approach could play an important role toward stabilizing the oil field' production. In addition, this technique could be extended fracture exploration in other oil fields producing substantial economic reward.

弱各向异性介质中传播的地震波及其速度重建

We begin our studies to make the best of information of seismic data and carry out the description of cracks parameters by extracting anisotropic information. The researching contents are: (1) velocity and polarization anomaly of seismic wave (qP and qSV wave) in weak anisotropic media; (2) reflection seismic synthetic record in anisotropic media; (3) multiple scattering induced by cracks; (4) anisotropic structure inversion and velocity reconstruction with VSP (Vertical Seismic Profile) data; (5) multi-parameters analysis of anisotropy in time-domain and depth-domain. Then we obtain results as follows: (1) We achieve approximate relation of qP and qSV wave's velocity and polarization property in weak anisotropic media. At the same time, we calculate anisotropic velocity factors and polarization anomaly of several typical sedimentary rocks. The results show there are different anisotropic velocity factors and polarization anomaly in different rocks. It is one of the primary theoretical foundation which is expected to identify lithology; (2) We calculate reflection seismic synthetic record with theoretical model; (3) We simulate scattering induced by cracks with Boundary Element Method. Numerical studies show that in the presence of cracks; spatial and scale-length distributions are important and cannot be ignored in modeling cracked solids; (4) From traveltimes information of VSP data, we study the velocity parameter inversion of seismic wave under isotropic and anisotropic models, and its result indicate that the inversion imaging under anisotropic model will not destroy the original features of isotropic model, but it will bring on some bigger error if we adopt the method of isotropic model for anisotropic model data. Further more, basing on the study we develop the CDP mapping technology of reflecting structure under isotropic and anisotropic models, and we process real data as a trial of the methods; (5) We study the problem of initial model reconstruction of anisotropic parameters structure represented by Anderson parameter in depth domain for surface data.

各向异性介质中的地震面波和S波分裂

Surface wave propagation in the anisotropic media and S-wave splitting in China mainland are focused in this M.S. dissertation. We firstly introduced Anderson parameters in the research of surface wave propagation in the anisotropic media were deduced, respectively. By applying the given initial model to the forward calculation of Love wave, we compared dispersion curves of Love wave in the anisotropic media with the one in the isotropic media. the results show that, although the two kind of results are similar with each other, the effect of anisotropy can not be neglected. Furthermore, the variation of anisotropy factors will result in the variation of dispersion curves, especially for high-mode one. The method of grid dispersion inversion was then described for further tectonic inversion. We also deduced inversion equation on the condition that the layered media is anisotropic, and calculated the phase-velocity partial derivatives with respect to the model parameters, P- and S-wave velocities, density, anisotropic parameters for Rayleigh wave and Love wave. Having analyzed the results of phase-velocity partial derivatives, we concluded that the derivatives within each period decreased with the depth increasing, the phase-velocity of surface wave is sensitive to the S-wave velocities and anisotropic factors and is not sensitive to the densities of layers. Dispersion data of Love wave from the events occurred during the period from 1991 to 1998 around the Qinghai and Tibet Plateau, which magnitudes are more than 5.5, have been used in the grid dispersion inversion. Those data have been preprocessed and analyzed in the F-T domain. Then the results of 1°*1° grid dispersion inversion, the pure path dispersion data, in the area of Qianghai and Tibet Plateau were obtained. As an example, dispersion data have been input for the tectonic inversion in the anisotropic media, and the results of anisotropic factors under the region of Qianghai and Tibet Plateau were initially discussed. As for the other part of this dissertation. We first introduced the phenomena of S-wave splitting and the methods for calculation the splitting parameters. Then, We applied Butterworth band-pass filter to S-wave data recorded at 8 stations in China mainland, and analyzed S-wave splitting at different frequency bands. The results show the delay time and the fast polarization directions of S-wave splitting depend upon the frequency bands. There is an absence of S-wave splitting at the station of Wulumuqi (WMQ) for the band of 0.1-0.2Hz. With the frequency band broaden, the delay time of S-wave splitting decreases at the stations of Beijing (BJI), Enshi (ENH), Kunming (KMI) and Mudanjiang (MDJ); the fast polarization direction at Enshi (ENH) changes from westward to eastward, and eastward to westward at Hailaer (HIA). The variations of delay time with bands at Lanzhou (LZH) and qiongzhong (QIZ) are similar, and there is a coherent trend of fast polarization directions at BJI, KMI and MDJ respectively. Initial interpretations to the results of frequency band-dependence of S-wave splitting were also presented.

库车坳陷第三纪磁性地层和磁组构的研究

The Tertiary Kuche depression, also known as one of the most economically important oil and gas prospecting regions in the Tarim Basin, is a foreland basin formed by flexural subsidence resulting from the southward thrusting of the southern Tianshan. Detailed geological and geophysical studies on the Tertiary sequence of the Kuche region would provide constraints not only on the Mesozoic and Cenozoic deformation patterns, and its controlling on the formation and distribution of oil and gas of the Kuche depression, but also on the India-Asia postcollisional uplift and continental deformation of the Tianshan regions. In this thesis, the Tertiary sequence of the Kuche depression, which is composed of the upper Kumukeliemu Formation, Suweiyi Formation, Jidike Formation, Kangcun Formation, and Kuche Formation, was selected for magnetostratigraphic and anisotropy of magnetic susceptibility (AMS) study. Among a total of 697 collected sites, 688 sites gave magnetic fabric results and 686 sites yielded reliable paleomagnetic results, building up magenetostratigraphy for the Tertiary sequence of the Kuche depression. By correlating with international geomagnetic polarity timescale, the followings were concluded: 1) the time interval of the sampling sections is some 31-8.1 Ma; 2) the boundaries for Kangcun/Jidike Formations, Jidike/Suweiyi Formations, and Suweiyi/Kumukeliemu Formations are at about 13.5 Ma, 26 Ma and 29 Ma respectively; 3) the Jidike Formation might be formed in an interval between the late Upper Oligocene and middle Miocene, whereas the Suweiyi Formation was formed in the Upper Oligocene, in turn, the Paleogene/Neogene boundary is most likely to be at the bottom of the Jidike Formation in the Kuche depression; 4) the dramatic transition from the marine/lacustrine to fluvial/alluvial facies in the Suweiyi Formation and the lower Jidike Formation of the Kuche depression, which may indicate the initiation of Cenozoic thrusting in the Kuche depression, is probably occurred in the late Oligocene, i.e. at about 28-25 Ma. On the other hand, systematic differences of the AMS parameters, such as the corrected anisotropy of magnetic susceptibility, shape parameter of ellipsoids, q factors, angles between the intermediate and minimum magnetic susceptibility directions and bedding, indicate that a dramatic transition of tectonic strain is most likely to occur at about 16 Ma (middle Miocene) in the Kuche depression. Taking into account the initiation o f C enozoic thrusting in the Kuche d epression i s at about 2 8-25 M a, we argue that the intensive Cenozoic thrusting in the Kuche depression is mainly happened during a period between the late Oligocene to middle Miocene.

青藏高原东部电性结构特征及地球动力学意义

As the largest and highest plateau on the Earth, the Tibetan Plateau has been a key location for understanding the processes of mountain building and plateau formation during India-Asia continent-continent collision. As the front-end of the collision, the geological structure of eastern Tibetan Plateau is very complex. It is ideal as a natural laboratory for investigating the formation and evolution of the Tibetan Plateau. Institute of Geophysics, Chinese Academy of Sciences (CAS) carried out MT survey from XiaZayii to Qingshuihe in the east part of the plateau in 1998. After error analysis and distortion analysis, the Non-linear Conjugate Gradient inversion(NLCG), Rapid Relaxation Inversin (RRI) and 2D OCCAM Inversion algorithms were used to invert the data. The three models obtained from 3 algorithms provided similar electrical structure and the NLCG model fit the observed data better than the other two models. According to the analysis of skin depth, the exploration depth of MT in Tibet is much more shallow than in stable continent. For example, the Schmucker depth at period 100s is less than 50km in Tibet, but more than 100km in Canadian Shield. There is a high conductivity layer at the depth of several kilometers beneath middle Qiangtang terrane, and almost 30 kilometers beneath northern Qiangtang terrane. The sensitivity analysis of the data predicates that the depth and resistivity of the crustal high conductivity layer are reliable. The MT results provide a high conductivity layer at 20~40km depth, where the seismic data show a low velocity zone. The experiments show that the rock will dehydrate and partially melt in the relative temperature and pressure. Fluids originated from dehydration and partial melting will seriously change rheological characteristics of rock. Therefore, This layer with low velocity and high conductivity layer in the crust is a weak layer. There is a low velocity path at the depth of 90-110 km beneath southeastern Tibetan Plateau and adjacent areas from seismology results. The analysis on the temperature and rheological property of the lithosphere show that the low velocity path is also weak. GPS measurements and the numerical simulation of the crust-mantle deformation show that the movement rate is different for different terranes. The regional strike derived from decomposition analysis for different frequency band and seismic anisotropy indicate that the crust and upper mantle move separately instead of as a whole. There are material flow in the eastern and southeastern Tibetan Plateau. Therefore, the faults, the crustal and upper mantle weak layers are three different boundaries for relatively movement. Those results support the "two layer wedge plates" geodynamic model on Tibetan formation and evolution.

各向异性与非线性介质中弹性波场传播特征研究

The topic of this study is about the propagation features of elastic waves in the anisotropic and nonlinear media by numerical methods with high accuracy and stability. The main achievements of this paper are as followings: Firstly, basing on the third order elastic energy formula, principle of energy conservation and circumvolved matrix method, we firstly reported the equations of non-linear elastic waves with two dimensions and three components in VTI media. Secondly, several conclusions about some numerical methods have been obtained in this paper. Namely, the minimum suitable sample stepth in space is about 1/8-1/12 of the main wavelength in order to distinctly reduce the numerical dispersion resulted from the numerical mehtod, at the same time, the higher order conventional finite difference (CFD) schemes will give little contribution to avoid the numerical solutions error accumulating with time. To get the similar accuracy with the fourth order center finite difference method, the half truncation length of SFFT should be no less than 7. The FDFCT method can present with the numerical solutions without obvious dispersion when the paprameters of FCT is suitable (we think they should be in the scope from 0.0001 to 0.07). Fortunately, the NADM method not only can reported us with the higher order accuracy solutions (higher than that of the fourth order finite difference method and lower than that of the sixth order finite difference method), but also can distinctly reduce the numerical dispersion. Thirdly, basing on the numerial and theoretical analysis, we reported such nonlinear response accumulating with time as waveform aberration, harmonic generation and resonant peak shift shown by the propagation of one- and two-dimensional non-linear elasticwaves in this paper. And then, we drew the conclusion that these nonlinear responses are controlled by the product between nonlinear strength (SN) and the amplitude of the source. At last, the modified FDFCT numerical method presented by this paper is used to model the two-dimensional non-linear elastic waves propagating in VTI media. Subsequently, the wavelet analysis and polarization are adopted to investigate and understand the numerical results. And then, we found the following principles (attention: the nonlinear strength presented by this paper is weak, the thickness of the -nonlinear media is thin (200m), the initial energy of the source is weak and the anisotropy of the media is weak too): The non-linear response shown by the elastic waves in VTI media is anisotropic too; The instantaneous main frequency sections of seismic records resulted from the media with a non-linear layer have about 1/4 to 1/2 changes of the initial main frequency of source with that resulted from the media without non-linear layer; The responses shown by the elasic waves about the anisotropy and nonlinearity have obvious mutual reformation, namely, the non-linear response will be stronger in some directions because of the anisotropy and the anisotropic strength shown by the elastic waves will be stronger when the media is nonlinear.

西南天山托云盆地白垩-新生代古地磁结果及其构造意义

Western China is regarded as an assemblage of blocks or microplates. The India/Asia postcollisional kinematics of these blocks has attracted many geologists to pay attentions, especially on the geodynamics and intracontinental deformation of Tibetan and adjoining parts of central Asia. So far there are still many debates on the amount of continental shortening and extrusion within Western China blocks. Paleomagnetism plays a very important role in the paleogeographic reconstruction and depiction of kinematics of the blocks, however the unequilibrium of paleomagentic data obtained from Western China prevents paleomagnetists from studying the kinematics and intracontinental deformation on the Tibetan plateau and the central Asia. Moreover, shallower inclinations observed in the Cretaceous and Cenozoic terrestrial red sediments in central Asia makes it difficult to precisely estimate the northward convergence of Tibetan plateau and its adjacent areas since the onset of the Indian/Asian collision. In this thesis, detailed rock magnetic, chronological and paleomagnetic studies have been carried out on the Tuoyun Basin in the southwestern Tianshan to discuss the possible continental shortening and tectonic movements since the Cretaceous-Tertiary. Ar-Ar geochronological study has been conducted on the upper and lower basalt series from the Tuoyun Basin, yielding that the lower and upper basalt series were extruded during 115-113 Ma and 61.8-56.9 Ma, respectively. Both the age spectrum and inverse isochron show that the samples from the upper and lower basalt series have experienced no significant thermal events since extrusion of the baslts. Rock magnetic studies including temperature dependence of magnetization and susceptibility during a heating-cooling cycle from temperature up to 600 ℃ suggest that the baslt samples from the lower and upper basalt series are ferromagnetically predominant of magnetite and a subordinate hematite with a few sites of titanomagnetite. The predominant magnetic mineral of the intercalated red beds is magnetite and hematite. Anisotropy of magnetic susceptibility shows that both the baslts and the intercalated red beds are unlikely to have undergone significant strain due to compaction or tectonic stress since formation of the rocks. The stable characteristic remanent magnetization (ChRM) isolated from the most samples of the upper and lower basalt series and intercalated red beds, passes fold test at the 99% confidence level. Together with the geochronological results, we interpret the characteristic component as a primary magnetization acquired in the formation of rocks. Some sites from both the upper and lower basalts yielded shallower inclinations than the reference field computed from the Eurasia APW, we prefer to argue that these shallow inclinations might be related to geomagnetic secular variation, whereas the shallow inclination in the intercalated red beds is likely to be related to detrital remanent magnetization. Paleomagnetic results from the early Cretaceous-Paleogene basalts indicate that no significant N-S convergence has taken place between the Tuoyun Basin and the south margin of Siberia. Furthermore, the Cretaceous and Tertiary paleomagnetic results suggest that the Tuoyun Basin was subjected to a local clockwise rotation of 20°-30° with respect to Eurasia since the Paleocene time, which is probably subsequent to the Cenozoic northward compression of the Pamir arc.

泥河湾盆地磁性地层学研究——以东谷索和岑家湾剖面为例

The Nihewan Basin is a key area for research into human occupation at high northern latitudes in northeast Asia after the initial expansion of early humans out of Africa. Well-developed late Cenozoic lacustrine deposit sequence in this basin offers a unique opportunity to address this issue. In this thesis, detailed magnetostratigraphic investigation coupled with mineral magnetism was conducted on the Donggutuo and Cenjiawan sections in the eastern basin, where lacustrine deposits sequences containing the Donggutuo, Maliang and Cenjiawan Paleolithic sites are well developed. The sequences are mainly composed of grayish-white clays, grayish-green clayey silts, grayish-yellow silts and fine-grained brown sands, which have recorded reliable polarity variations of geomagnetic field.Characteristics of the anisotropy of magnetic susceptibility show that the sediments have preserved typical original magnetic fabric for sediments, indicating that the strata were developed in a low-energy lake environment and were never perturbed by tectonic stress since deposition. High-temperature magnetic susceptibility measurements (x-T) of representative specimens and demagnetization experiments indicate that the dominant magnetic mineral and remanent carrier at the two sections is magnetite. In addition, hematite and possibly minor maghemite exists in some portions of the sequences. The majority of the samples have relatively simple demagnetization behaviors. After removal of soft magnetic components, the stable characteristic remanent magnetizations (ChRMs) are isolated, which can represent the original remanences.The Donggutuo section mainly records the Brunhes chron, the Matuyama chron and the Jaramillo subchron. The Maliang stone artifact layer occurs just below the Brunhes/Matuyama boundary; and the Donggutuo artifact layer, just below the Jaramillo onset. Accordingly, the Maliang and Donggutuo sites can be dated at about 0.78 Ma and 1.1 Ma, respectively. The Cenjiawan section has recorded a portion of the Matuyama chron. After correlations with the magnetic polarity sequence of the Majuangou section adjacent to this section, the Cenjiawan stone artifact layer is determined below the Jaramillo onset, with an estimated age of 1.1 Ma.To establish the magnetic stratigraphy framework for the lacustrine sediments in the eastern Nihewan Basin, this thesis draws on the magnetic polarity sequences of the Donggutuo and Cenjiawan sections as well as previously obtained results from the Majuangou, Haojiatai, Xiaochangliang and Donggou sections for magnetostratigraphic correlations. The accumulation of the lacustrine sequences at the east margin of the basin commenced from about 2.0 Ma. These sequences record not only the coarse magnetostratigraphy of the Brunhes normal chron and the middle to late Matuyama reverse chron (that is, the Jaramillo and Olduvai subchrons) but also some of the fine structure (that is, the Kamikatsura, Santa Rosa, Punaruu and Cobb Mountain geomagnetic events). The development of the Nihewan paleolake experienced at least twice large expansion periods, split by a large-scale shrinking event in the middle period of the paleolake development. The accumulation of the lacustrine strata was controlled by fault activities.After temporal control for the Donggutuo, Maliang and Cenjiawan Paleolithic sites were established, the three sites along with other well-dated Paleolithic/hominin sites of the Early Pleistocene in North China were combined to construct a chronological sequence of early human occupation in northeastern Asia. Furthermore, after incorporation of paleoclimate changes retrieved from Chinese loess/paleosol sequences and marine sediments, it could be possibly proposed that human groups of the Early Pleistocene in North China might have survived repeated warm/humid interglacials and cold/dry glacials, which were paced by earth orbital variations of the Eastern paleomonsoon.

多波分量地震资料处理解释方法

To deal with some key problems in multi-component seismic exploration, some methods are introduced in this thesis based on reading amounts of papers about multi-component seismic theories and methods. First, to find a solution for the detection of the fracture density and orientation in igneous, carbonate and shale reservoirs, a large amount of which exist in domestic oil fields with low exploration and development degree, a new fast and slow shear waves separation method called Ratio Method based on S-wave splitting theory is discussed in this thesis, through which the anisotropy coefficient as well as fracture parameters such as density and azimuthal angle can be acquired. Another main point in this thesis involves the application of seismic velocity ratio (Vp/Vs) to predict the Hthological parameters of subsurface medium. To deal with the unfeasibility of velocity ratio calculation method based on time ratio due to the usually low single-noise ratio of S-wave seismic data acquired on land, a new method based on detailed velocity analysis is introduced. Third, pre-stack Kirchhoff integral migration is a new method developed in recent years, through which both S and P component seismic data as well as amplitude ratio of P/S waves can be acquired. In this thesis, the research on untilizing the P and S wave sections as well as amplitude ratio sections to interpret low-amplitude structures and lithological traps is carried out. The fast and slow shear wave separation method is then be applied respectively to detect the density and azimuthal angle of fractures in an igneous rock gas reservoir and the coal formation in a coal field. Two velocity ratio-calculating methods are applied respectively in the lithological prediction at the gas and coal field after summarizing a large amount of experimental results draw domestically and abroad. P and S wave sections as well as amplitude ratio sections are used to identify low-amplitude structures and lithological traps in the slope area of a oil-bearing sedimentary basin. The calculated data concerning fracture density and azimuthal angle through the introduced method matches well with the regional stress and actual drilling data. The predicted lithological data reflects the actual drilling data. Some of the low-amplitude and lithological traps determined by Kirchhoff migration method are verified by the actual drilling data. These results indicate that these methods are very meaningful when dealing with complex oil and gas reservoir, and can be applied in other areas.