起伏地表谱元逆时偏移方法

谱元法综合了有限元法边界适应性强和谱方法精度高、收敛快的优点.研发了一种基于谱元法的起伏地表逆时偏移方法,采用切比雪夫谱元法并结合隐式Newmark时间积分法求取波场传播算子,推导出波动方程切比雪夫谱元逆时偏移算法(CSE-R T M),该算法在空间上具有谱精度,在时间上达到二阶精度.同时,为了充分利用计算机集群资源,...

Reverse time migration for irregular topography based on spectral element method

The spectral element method combines the advantages of strong boundary adaptability of the finite element method and high accuracy and fast convergence of the spectral method.For the high-precision seismic imaging of complex structures with irregular topography,a Chebyshev spectral-element reverse time migration method(CSE-RTM)was proposed.Using this method,the wave field propagation operator is obtained through the Chebyshev spectral element method coupled with the implicit Newmark time integral method.The method offers spectral accuracy in space and second-order accuracy in time.To improve the parallel efficiency,based on the concepts of cohesion degree and local relaxation,an integrated hierarchical equilibrium parallel Chebyshev spectral-element reverse time migration(HEP-CSE-RTM)algorithm was developed,which is a fine-grained central processing unit parallel computation method in two-level host-sub-processor mode.The advantage of this algorithm is that the parallel efficiency does not decrease as the number of processors increases.Model tests showed that in a complex structure with irregular topography,the imaging accuracy of the HEP-CSE-RTM algorithm was higher than that of the conventional finite-difference reverse time migration method(FD-RTM).Owing to the fast convergence of the spectral method on a sparse grid coupled with a parallel computational scheme,the calculation efficiency of the HEP-CSE-RTM is equivalent to that of the FD-RTM.