有效利用初至信息的偏移距加权地震层析成像方法  

Offset-weighted seismic tomography aimed at using the first arrival efficiently

作　　者：刘玉柱[1,2] 杨积忠[2] 

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092 [2]同济大学海洋与地球科学学院,上海200092

出　　处：《石油物探》2014年第1期99-105,115,共8页Geophysical Prospecting For Petroleum

基　　金：国家自然科学基金(41274116);海洋地质国家重点实验室课题(MGG2013001)共同资助

摘　　要：在基于射线理论的初至波地震走时层析成像方法中,很多因素会影响反演效果,其中观测数据能否有效利用是影响反演结果精度的一个重要因素。数值实验表明,初至层析成像反演表层速度结构时,不同偏移距数据对于提高不同深度反演精度的贡献是不同的。根据这一认识,提出了多偏移距(MOR)层析反演策略,以提高表层建模反演的精度;通过理论模型与实际资料测试证实了该策略的有效性。但MOR反演策略实现过程复杂,且只能实现偏移距的离散利用,考虑到多偏移距层析实质上是对观测数据的一种加权实现,进一步提出了利用偏移距构建协方差矩阵的偏移距加权地震层析成像方法。模型数据与实际资料的反演实验结果表明,偏移距加权地震层析成像方法避免了MOR层析过程中的多次嵌套反演,只需一次反演就可以达到连续多偏移距层析策略的反演效果。In ray-based first arrival seismic traveltime tomography,the inversion result is affected by many factors.Whether the observed data can be used efficiently is an important factor.Through numerical simulation it is discovered that,when first arrival tomography is used to inverse the near surface structure,the influence of observed data on inversion accuracy at different depth varies from offset.According to this recognition,a new strategy called multi-offset ranges （MOR） tomography is proposed to enhance the accuracy of surface inversion.Experiments on theoretical data and field data prove the effectiveness of this strategy.However,the performance of MOR tomography is complicated,and only some discrete offsets can be used.Considering that MOR is essentially a kind of weighted function of observed data,the offset information can be used to construct the covariance matrix of tomographic objective function.As a result,a new method called offset-weighted seismic tomography is presented.This new tomographic method is also proved effective through numerical experiments and real data inversion,which can be applied to achieve sequential MOR tomography through one inverse procedure instead of the complicated performance of MOR tomography.

关 键 词：初至波 层析成像 反演策略 偏移距加权 协方差矩阵 

分 类 号：P631.4[天文地球—地质矿产勘探]