一种变网格差分的快速行进法

地震波旅行时精度直接影响着地震反演、叠前偏移成像、层析成像等各领域研究成果的可靠性,因此,研究如何提高地震波旅行时精度是很有意义的。在双重网格技术的基础上,引入一种基于变网格差分格式的快速行进法(FMM)计算地震波旅行时,通过正演模拟均匀模型、存在高速异常体模型、Marmousi模型来分析变网格FMM的优势及适用性。研究结果表明:均匀模型背景下,变网格FMM与双重网格FMM优势相当,但是在存在高速异常体模型背景下,双重网格FMM可能违背波前扩展的规律,从而导致较大的误差,而变网格FMM则不存在这样的问题; Marmousi模型试算验证了变网格FMM能适应各种复杂模型。因此,该方法是一种有效提高走时计算精度和效率的方法,不仅增强了FMM法的适用性,而且扩展了变网格技术的应用范围。

A grid-variable finite-difference fast marching method

The accuracy of seismic wave traveltimes directly affects the reliability of research results in such fields as seismic inversion,pre-stack migration imaging and tomography.Therefore,it is of great significance to study the improvement of the accuracy of seismic wave traveltimes.Based on the double grid technology,this paper comes up with a fast marching method (FMM) based on the grid-various finite-difference scheme to calculate the traveltimes of seismic wave.It analyzes the advantages and applicability of the grid-various finite-difference FMM by the forward simulation of uniform model as well as the existence of high-speed anomalous body model,Marmousi model.The results show that the corner points need to be included in the calculation when the traveltimes are calculated by using Eikonal equation so as to reduce the error.Under the background of uniform model,the grid-variable finite-difference FMM has the same advantages as the double grid FMM.Nevertheless,under the background of the existence of high-speed anomalous body model,the double grid FMM may violate the law of wavefront expansion to cause a greater error.The grid-variable finite-difference FMM does not have such a problem,and its advantage is remarkable.Therefore,this method is an effective way to improve the accuracy and efficiency of traveltime calculation,which not only enhances the applicability of the FMM but also expands the application range of grid-various technology.