TI介质局部角度域射线追踪与叠前深度偏移成像   总被引：1，自引：1，他引：0       下载免费PDF全文

段鹏飞  程玖兵  陈三平  何光明 《地球物理学报》2013,56(1):269-279

研究与实践表明,对于长偏移距、宽方位地震数据,忽略各向异性会明显降低成像质量,影响储层预测与描述的精度.针对典型的横向各向同性(TI)介质,本文面向深度域构造成像与偏移速度分析的需要,研究基于射线理论的局部角度域叠前深度偏移成像方法.它除了像传统Kirchhoff叠前深度偏移那样输出成像剖面和炮检距域的共成像点道集,还遵循地震波在成像点处的局部方向特征、基于扩展的脉冲响应叠加原理获得入射角度域和照明角度域的成像结果.为了方便快捷地实现TI介质射线走时与局部角度信息的计算,文中讨论和对比了两种改进的射线追踪方法:一种采用从经典各向异性介质射线方程演变而来的由相速度表征的简便形式;另一种采用由对称轴垂直的TI(即VTI)介质声学近似qP波波动方程推导出来的射线方程.文中通过坐标旋转将其扩展到了对称轴倾斜的TI(即TTI)介质.国际上通用的理论模型合成数据偏移试验表明,本文方法既适用于复杂构造成像,又可为TI介质深度域偏移速度分析与模型建立提供高效的偏移引擎.  相似文献   

Research Note the Matrix Element For A Transversely Isotropic Earth Model     

Naoki Shibata  Naoki Suda  Yoshio Fukao 《Geophysical Journal International》1990,100(2):315-318

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The Transition Between the Scale Domains of Ray and Effective Medium Theory and Anisotropy: Numerical Models   总被引：1，自引：0，他引：1  

Yinbin Liu  Douglas R. Schmitt 《Pure and Applied Geophysics》2006,163(7):1327-1349

The anisotropy of a periodically layered isotropic medium is numerically modeled in order to study the effect of the scale of heterogeneity on seismic observations. An important motivation is to delineate the wavelength ranges over which a pulse propagating obliquely through the structure will be described by either ray (short wavelength) or effective medium (long wavelength) theory. The same band-limited pulse is propagated obliquely at a variety of incidence angles through a compositionally uniform layered structure as a function of the layer thicknesses. The resulting seismograms display similar behavior to that encountered for normal incidence including the effects of stop- and pass-bands. Velocities determined from time picks on these seismograms show a large difference in velocities between the long and short wavelength limits as has been previously demonstrated for normal incidence propagation. The bulk of the transition between these two limits is independent of incidence angle and occurs when the ratio between the wavelength and the layering thickness is near a value of 10. Two more geologically reasonable models show that these effects are diminished with smaller contrasts between the layers.  相似文献   

Surface deformation due to loading of a layered elastic half-space: a rapid numerical kernel based on a circular loading element   总被引：1，自引：0，他引：1  

E. Pan  M. Bevis  F. Han  H. Zhou  R. Zhu 《Geophysical Journal International》2007,171(1):11-24

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Some Thoughts On Local Isotropy And The 4/3 Lateral To Longitudinal Velocity Spectrum Ratio     

C. A. Biltoft 《Boundary-Layer Meteorology》2001,100(3):393-404

Applications of Kolmogorov's universal equilibrium hypothesis and the Taylor transform to velocity spectra derived from measurements within the low frequency portion of the atmospheric surface layer (ASL) inertial subrange are examined. The measured ratios of lateral to longitudinal velocity component spectra exhibit considerable scatter, but suggest convergence towards 1.0 rather than towards the 4/3 expected from theory. Shear and buoyancy introduce anisotropy to the inertial subrange, thereby contributing to the observed scatter. The apparent discrepancy between the 4/3 velocity component spectrum ratio expected from theory and the measurements could arise as a consequence of the processing used to produce spectra. These processing effects must be considered from the perspective of the propagating eddy. Spectral averaging used with sonic anemometer data is done over time periods that are large with respect to inertial subrange eddy correlation decay times. This averaging causes energy from larger scale eddies to appear as `local convection' that dominates the Taylor transform. Spectrum ratio convergence and cospectra approaching zero are necessary, but not sufficient, conditions for onset of local isotropy. Measurements of spectrum ratios and cospectra over the entire inertial subrange are needed to determine whether or not local isotropy might occur within the ASL.  相似文献   

Vertical seismic profile at Pike's Peak, Saskatchewan, Canada: turning rays and velocity anisotropy     

Rachel T. Newrick  Don C. Lawton 《Journal of Applied Geophysics》2003,54(3-4):401

First-arrival traveltimes from a multi-offset vertical seismic profile (VSP) were used to estimate velocity anisotropy in the presence of a vertical velocity gradient. A numerical model consisting of two layers with vertical velocity gradients of 3.1 and 1.2 s⁻¹, respectively, and global anisotropy parameters of =0.12±0.02 and δ=0.30±0.06 yielded first-arrival traveltimes that matched the observed traveltimes well. Shallow receivers were found to be crucial for constraining the vertical velocity field and for determining the parameters of anisotropy at depth.  相似文献   

Kriging of Regionalized Directions, Axes, and Orientations II: Orientations     

K. Gerald van den Boogaart  Helmut Schaeben 《Mathematical Geology》2002,34(6):671-677

The problem to predict a rotation (orientation) from corresponding geocoded data is discussed and a general solution by virtue of embedding the group of rotations in a real vector space is presented. It is referred to as kriging in embedding spaces as developed in part I of this contribution, and basically the same arguments apply and lead to equivalent results. However, the assumptions of isotropy have to be restated and reinterpreted. A one-to-one correspondence of reasonable isotropy assumptions for rotations represented as axes and for rotations represented by matrices does not seem to exist.  相似文献   

Reducing the grid orientation dependence of flow routing on square-grid digital elevation models   总被引：1，自引：0，他引：1  

Jari Hyväluoma 《International journal of geographical information science》2017,31(11):2272-2285

Topographical parameters derived from digital elevation models by employing flow routing algorithms may depend on the orientation of the square grid. Grid orientation dependence results from the insufficient isotropy of square grid and affects the flow directions and subsequent calculations based on flow routing. In this article, a systematic approach for analysing the rotational invariance of flow accumulation calculations is presented and applied. Computed flow accumulation maps are found to depend strongly on the grid orientation, especially if flow routing methods with low dispersion are used. It is also shown that isotropy of flow routing algorithms can be significantly improved by introducing a numerical parameter resulting in adjustable weighting for cardinal and diagonal directions in flow routing. The actual value of this parameter depends on the used flow routing method.  相似文献   

横向各向同性介质二维格林函数的F-K算法   总被引：2，自引：0，他引：2       下载免费PDF全文

何樵登  阎贫 《地球物理学报》1994,37(5):667-672

采用算子表示法，在Ｆ-Ｋ域内将横向各向同性介质中的波动方程进行算子分解，然后利用留数定理求出格林函数的解析解。并给出了一个算例，得出时空域中ｑＰ波、ｑ（ＳＶ）波和Ｑ_ｓＨ波的格林函数剖面。  相似文献   

Time-harmonic response of transversely isotropic multilayered half-space in a cylindrical coordinate system     

《Soil Dynamics and Earthquake Engineering》2014

With the aid of the analytical layer-element method, a comprehensive analytical derivation of the response of transversely isotropic multilayered half-space subjected to time-harmonic excitations is presented in a cylindrical coordinate system. Starting with the governing equations of motion and the constitutive equations of transversely isotropic elastic body, and based on the Fourier expansion, Hankel and Laplace integral transform, analytical layer-elements for a finite layer and a half-space are derived. Considering the continuity conditions on adjacent layers׳ interfaces and the boundary conditions, the global stiffness matrix equations for multilayered half-space are assembled and solved. Finally, some numerical examples are given to make a comparison with the existing solution and to demonstrate the influence of parameters on the dynamic response of the medium.  相似文献