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频率空间域地震波数值模拟具有独特的优势:可以同时模拟多源的波传播、每个频率之间独立并行地计算、计算频带选择灵活、不存在累计误差、容易模拟粘弹性介质中地震波传播。但是该方法的最大瓶颈是对于计算机内存的巨大需求。我们使用压缩存储系数矩阵的方法,极大地减少了计算机内存的需求量。同时为了减少短差分算子的数值频散,引用了频率空间域25点弹性波波动方程的差分格式,并使用了最小二乘意义下求出的优化差分系数。为了克服边界反射,采用了最佳匹配层吸收边界条件。数值模拟试验证明:用压缩存储系数矩阵及优化差分系数的频率空间域25点差分格式进行弹性波正演模拟,可以减少数值频散,提高计算精度。使用较大的网格间距,降低计算机内存需求,并保持较高的计算效率。该正演方法为后续弹性波偏移和弹性参数反演提供较好的基础。
The numerical simulation of frequency-space-domain seismic waves has unique advantages: it can simultaneously simulate multi-source wave propagation and calculate independently and independently of each frequency. The calculation of frequency bands is flexible and there is no accumulated error, which makes it easy to simulate seismic wave propagation in viscoelastic media. But the biggest bottleneck for this approach is the huge need for computer memory. We use the method of compressing the storage coefficient matrix, which greatly reduces the demand for computer memory. At the same time, in order to reduce the numerical dispersion of the short differential operator, the difference scheme of the 25-point elastic wave equation in the frequency-space domain is used and the optimal differential coefficient is obtained in the sense of least square. In order to overcome the boundary reflections, the optimal matching layer absorption boundary conditions are used. Numerical simulations prove that the elastic wave forward modeling using the 25-point difference frequency-space domain of the compressed storage coefficient matrix and the optimized differential coefficient can reduce the numerical dispersion and improve the calculation accuracy. Use a larger grid spacing to reduce the computer memory requirements, and maintain a high computational efficiency. The forward method provides a good foundation for subsequent elastic wave migration and elastic parameter inversion.