Higher-Order Rytov Approximation for Large-Scale and Strong Perturbation Media  

作　　者：Bo Feng Ru-Shan Wu Huazhong Wang 

机构地区：[1]Wave phenomena and inversion imaging group(WPI),School of Ocean and Earth Science,Tongji University,Shanghai,200092,China [2]Modeling and Imaging Laboratory,University of California,Santa Cruz,95060,CA,USA

出　　处：《Communications in Computational Physics》2020年第6期98-110,共13页计算物理通讯（英文）

基　　金：supported by National Natural Science Foundation of China(41604091,41704111,41774126);the great and special project(2016ZX05024-001,2016ZX05006-002).

摘　　要：In the field of geophysics,although the first-order Rytov approximation is widely used,the higher-order approximation is seldom discussed.From both theo-retical analysis and numerical tests,the accumulated phase error introduced in the first-order Rytov approximation cannot be neglected in the presence of strong velocity perturbation.In this paper,we are focused on improving the phase accuracy of forward scattered wavefield,especially for the large-scale and strong velocity pertur-bation case.We develop an equivalent source method which can update the imaginary part of the complex phase iteratively,and the higher-order scattered wavefield can be approximated by multiplying the incident wavefield by the exponent of the imaginary part of the complex phase.Although the convergence of the proposed method has not been proved mathematically,numerical examples demonstrate that our method can produce an improved accuracy for traveltime(phase)prediction,even for strong perturbation media.However,due to the neglect of the real part of the complex phase,the amplitude change of the scattered wavefield cannot be recovered.Furthermore,in the presence of multi-arrivals phenomenon,the equivalent scattering source should be handled carefully due to the multi-directions of the wavefield.Further investigations should be done to improve the applicability of the proposed method.

关 键 词：Rytov approximation higher-order approximation large-scale strong perturbation forward scattering equivalent scattering source 

分 类 号：O17[理学—数学]