浅层地震反射资料的多阶振型面波反演

摘要

浅层地震反射波法和面波方法是两种相互独立发展的地震勘探方法,在各自的数据采集和处理中,对方都是作为干扰信号而存在.本文利用浅层地震反射资料中被视为干扰的面波信号,通过成熟的多道面波勘探技术处理浅层地震反射资料,在频率-波数域中提取多阶振型面波的频散曲线,并基于该曲线反演浅地表S波速度结构.这种方法充分开发利用了已有数据,无需单独的面波数据采集系统,同时为解释浅层地震反射资料提供了额外的信息约束.结果表明:浅层地震反射资料中可提取出可靠的多阶振型面波频散曲线,并能给出稳定的反演结果,同时,面波反演的多解性可以通过高阶振型反演得以进一步约束;低速层的存在是观测频散曲线出现振型跳跃或呈“之”字形回折的必要条件而非充分条件.%Shallow seismic reflection and surface wave are two seismic exploration methods which are developing independently.In their respective data collection and processing,the concerned signal in one method is usually thought as the disturbed one in the other method.In this paper,the "disturbed" surface wave occurred in the data collected by shallow seismic reflection survey was reused.The dispersion curves of multi-mode surface waves were extracted in the frequency-wave number domain based on these data by applying the multi-channel surface wave technology.The S-wave velocity profiles were then inversed by taking the fundamental and/or first-order modes into account.This method fully exploited the existing data.Therefore,the special data collection for surface waves is not needed,and additional constraint is offered to the interpretation of shallow seismic reflection data.The results indicate that the reliable multimode dispersion curves of surface waves can be extracted from the shallow seismic reflection data,and stable S-wave velocity profile can be obtained.Meanwhile,it is concluded that the existence of low-velocity layer is the necessary rather than the sufficient condition to make the observed dispersion curve exhibit the mode-jumping among the mode branches.