| Cross-hole seismic has been applied in project extensively because of many advantages, such as multi-wave receiving, high accuracy, high resolution, short of energy propagation length, approach detecting object, avoiding low speed zones. But because of the complexity and diversity of cross-hole seismic wave, for understanding the distributing instance of different wave field component in homogeneous half space effectively, analysis diversified detailed characteristics of kinematics and dynamics of reflection, transmission, diffraction, scattering and power attenuation in cross-hole seismic, and for better geological explanations, this text develops the forward simulation based on the cross-hole seismic wave equation and the seismic tomography technology. Based on the long time research and application of seismic tomography technology in water resources and hydropower project, the author sums up some important technology measures in project application, which could provide scientific basis and guiding meaning for the development and application of tomography technology of project cross-hole seismic. For the forward simulation and tomography technology of project cross-hole seismic wave, this text develops the below works:(1)When doing the cross-hole seismic tomography in water resources and hydropower project, the depth of the hole is small, and most of them are less than 100 meters. when the seismic source, wave detector are close to the ground or the top of water level surface in the hole, the influence of ground and the water level surface could not be ignored. So, in this text, combining with the characteristic of water resources and hydropower project, the author establishes cross-hole seismic model including ground and water level surface in the hole, does the forward simulation to it, calculate and completely analysis the propagation rule and characteristic of wave field in different field source and different particle velocity.(2)Based on systematically summing up the previous author's research and the mainly seismic wave field forward calculation method, the author derives first-order coupled elastic equations of 2D and 3D particle velocity and stress and the any order accurate time and space formulation of staggered-grid, finite-difference scheme. During the forward simulation calculation, the author takes irregular variable finite grids and variable time step theory. This would improve the calculation speed while guarantee the accuracy.(3)The author discusses detail the stability condition of staggered-grid, finite-difference method, and gets the stability condition which the time and space sampling step of high order accuracy difference must be satisfied. Analysis the reason of seismic wave numerical dispersion, and discusses the two dispersion compacting methods which are FCT and improving finite-difference accuracy. Conclude the classify method of some classical absorbing boundary condition and the advantages and disadvantages of them, then mainly introduces the basic theory used in forward simulation of PML absorbing boundary condition, and derives 2D or 3D PML absorbing boundary condition of first-order coupled elastic equations of particle velocity and stress in isotropic media. This could set the foundation for the cross-hole seismic wave field and the according program compiling.(4)Combining with Visual C++ visual program design language, compiles difference seismic wave forward program of cross-hole staggered-grid. Then apply this program into the forward simulation calculation of typical project geological models, and get the wave field snapshot and seismic record of the according model. In these results, it could clearly observe the kinematics and dynamics characteristics of primary wave, reflection wave, transmission wave and multiple wave of reflection. By analysis these forward record and wave field snapshot, it could understand the propagation regulation of seismic wave field more profundity, improve the comprehension to cross-hole seismic wave field snapshot and provide the technology support to the inversion interpretation. Moreover, do the whole wave field forward simulation to the seismic wave produced in quick, slow formation of different force source (level direction single force source and level direction double force source). It could get the seismic record and wave field snapshot of pressure, level stress, level particle velocity and vertical particle velocity. By the whole wave field simulation of this cross-hole seismic, it could grasp the characteristic of different field source and particle velocity completely.(5)analysis in detail the theory of travel-time tomography, sum up the advantages and disadvantages of different tomography ray tracing technology, and compare the advantages and disadvantages of ART and SIRT by applying them to rebuilding the numerical model separately. Based on this, the author compiles the inversion tomography process systematic software. By the forward simulation and inverse imaging of square defect model and cross fracture model in four sides and two sides observing system, it could research the influence of observing system to the imaging accuracy deeply. Comprehensively utilizing the geologic geophysical data, velocity logging, hole imaginary and seismic record, put forward the comprehensive method of setting up the initial velocity model, and gets the more accuracy and clearly inversion imaging effect.Then, deeply discuss the mechanism of seismic wave absorbing tomography; get the seismic absorbing tomography method, which could provide the useful supplement for the seismic wave absorbing tomography. According to the advantages and disadvantages of these two tomography technology method, the author puts forward utilizing multi-parameter to integrate the seismic tomography, which could make the wave velocity tomography and absorption tomography to makeup and confirm each other. The author applies these to project practice, which could improve the interpretations accuracy of seismic tomography technology in project, and provide more abundant basis to geological interpretations and project diagnose.
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