【作者】 戚艳平；

【导师】 吴国忱；

【作者基本信息】 中国石油大学 ， 地球探测与信息技术， 2008， 硕士

【摘要】 地球介质的各向异性是普遍存在的,地震各向异性研究已经成为地震学研究领域中的前沿课题之一。地震波正演模拟是模拟地震波在地球介质中的传播过程,并研究地震波的传播特性与地球介质参数的关系,通过正演模拟以达到对实际观测地震记录的最优逼近。开展地震波的正演模拟研究,对人们正确认识地震波的传播规律,验证所求地球模型的正确性;进行实际地震资料的地质解释与储层预测以及地球资源开发等,均具有重要的理论和实际意义。本文对具有垂直对称轴的三维横向各向同性(VTI)介质qP波在频率域和时间域进行了正演模拟。在频率域正演中,从三维VTI介质频率空间域qP波波动方程出发,在常规差分算子的基础上构造了适合三维VTI介质的频率空间域加权平均有限差分算子,利用Gauss-Newton优化方法算出VTI介质加权平均差分算子系数,并对常规差分算子和加权平均差分算子进行了速度频散精度对比分析。本文把螺旋边界和吸收边界应用在频率域正演上,在求取大型带状稀疏差分矩阵方面,作者提出了改进算法;并给出了三维频率域正演的数值实例。在三维VTI介质qP波时间域正演模拟方面,首先对三维VTI介质qP波时间域波动方程进行降阶处理,接着利用提出的加权平均差分算子对波动方程进行差分,并对加权平均差分算子进行了速度频散精度对比分析,还提出了一种新的分裂的完全匹配层来处理时间域边界,并进行了边界处理效果对比分析,最后进行了三维时间域正演模拟。频率域和时间域数值模拟表明:本文提出的算法有效地压制了数值频散,成功地减少了人为边界反射,具有较高的模拟精度,为三维VTI介质qP波的偏移和反演奠定了理论基础。更多还原

【Abstract】 Anisotropy is ubiquitous in earth media. Study on seismic anisotropy has become one of the leading edge directions in the field of seismology. Forward modeling simulates wave propagate in the media of earth. We can learn the relationship of characteristic of seismic propagate and the parameter of earth media from the simulating, and get the optimal approximation of real seismic recording. Studying on seismic forward modeling can help people accurately know the rule of seismic propagation. It also can verify the validity of earth model, interpret the real seismic data, predict reservoir and develop the resource. In a word, it has very important meaning in both theory and practice.This paper simulates the qP wave in 3-D transversely isotropy with a vertical axis of symmetry (VTI) media in both domains of frequency and time. In frequency domain modeling, stating with frequency-space domain qP wave equation in 3-D VTI media, the weighted mean finite difference operators which is based on conventional finite difference operators is presented. Comparing the precision of velocity dispersion of conventional finite difference operators and weighted mean finite difference is following. Then we get the weighted mean coefficient by the Gauss-Newton method in optimization theory to make the finite-difference equation phase velocity being equal to that of wave equation. The helix boundary condition and absorb boundary condition in frequency domain is adopted. In aspect of solving large sparse matrix this paper advances the improved arithmetic. The numerical experiments are given in the end of frequency domain modeling. In time domain modeling, we firstly deflate the time domain qP wave equation in 3-D VTI media. Secondly, apply the weighted mean finite difference operators which are presented former to the wave function in time domain. A new split perfect matched layer boundary condition is presented and is validated the effect in this paper. The complex model simulating in time domain is given at last. The model simulating of frequency and time domains show that the arithmetic that is given in this paper effectively suppress the numerical dispersion and successfully decrease the artificial boundary reflecton. It is supply the foundation for migriation and invertion of qP wave in 3-D VTI media.更多还原