地震虚源法边界效应研究  

Research on the boundary effect of seismic source method

作　　者：王冲鹏 刘怀山[1,2,3] WANG ChongPeng;LIU HuaiShan(College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Key Lab of Submarine Geoscience and Prospecting Techniques,MOE,Ocean University of China,Qingdao 266100,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266071,China)

机构地区：[1]中国海洋大学海洋地球科学学院,青岛266100 [2]海底科学与探测技术教育部重点实验室,青岛266100 [3]海洋国家实验室海洋矿产资源评价与探测技术功能实验室,青岛266071

出　　处：《地球物理学进展》2021年第3期1111-1121,共11页Progress in Geophysics

基　　金：国家自然科学基金(91958206,41230318);国家高技术研究发展计划(863计划)(2013AA092501)联合资助。

摘　　要：地震虚源法能够通过重建震源位置来避免复杂覆盖层的影响,因而广泛应用于时移地震监测和复杂覆盖层下的地震成像问题.由于在野外实际勘探过程中,震源只能布设于地表或靠近地表的有限范围内,无法沿地表无限延伸,因而在虚源反射记录中产生边界效应,影响格林函数的恢复质量.本文从理论模型出发推导有限孔径下边界效应的理论值,解释边界效应的产生原因及其表现形式,定量分析其主要影响因素并通过正演模拟进行说明,从而为虚源成像观测系统的设计提供指导性建议.边缘道衰减法可以对虚源反射记录中的边界效应进行有效压制,通过分析窗函数对互相关道集的衰减特性可以阐明边缘道衰减法的数学原理,并以此为依据计算边缘道的最佳理论衰减范围.边界效应和空间假频在时间上是密切相关的,基于稳相位分析的结果指出,互相关道集非稳相位域在不同位置的不完全叠加分别产生了边界效应和空间假频,这表明空间假频的压制可以通过对边缘道衰减法中衰减范围的合理选取来实现,从而将边缘道衰减法的应用范围进一步推广至对空间假频的压制中.Seismic virtual source method can avoid the influence of complex overburden by reconstructing the source location, so it is widely used in time-lapse seismic monitoring and seismic imaging under complex overburden. In actual field exploration, the seismic source can only be placed on or close to the surface within a limited range, and the source-line cannot extend indefinitely along the surface. Therefore, boundary effects occur in the virtual source reflection records, which affects the recovery quality of the Green function. In this paper, the theoretical value of the boundary effect under finite aperture is deduced from a homogeneous medium model which includes two horizontal layers. On this basis, the cause of the boundary effect and its manifestation are further clarified, its main influencing factors are quantitatively analyzed and explained through forward modeling, such works provide guidance suggestions for the design of virtual source imaging observation system. The edge channel attenuation method can be regarded as an effectively method to suppress the boundary effect in the virtual source reflection records. Based on the theoretical value of the boundary effect under the finite aperture, the mathematical basis of the edge channel attenuation method can be clarified by the attenuation characteristics of the window function, which also provides a basis for the selection of the theoretical optimal attenuation range of the edge channel. In the virtual source reflection records, there is a certain relationship between the boundary effect and the spatial aliasing in the appearance time, which can be explained by the stationary phase analysis. The results based on the stationary phase analysis indicate that the boundary effect and the spatial aliasing are caused by the incomplete superposition of the nonstationary phase domain of cross-correlation gathers at different positions. We will see that by re-selecting the attenuation range of the edge channel attenuation method, the suppression of spatial aliasing

关 键 词：地震虚源法 边界效应 稳相位分析 空间假频 边缘道衰减法 

分 类 号：P631[天文地球—地质矿产勘探]