一种基于层析成像技术提高浅地表面波勘探水平分辨率的方法  

A travel-time tomography method for improving horizontal resolution of high-frequency surface-wave exploration

作　　者：尹晓菲 胥鸿睿 夏江海 孙石达 王芃[1] YIN XiaoFei;XU HongRui;XIA JiangHai;SUN ShiDa;WANG Peng(Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China;Subsurface Imaging and Sensing Laboratory, China University of Geosciences, Wuhan 430074, China;School of Earth Sciences, Zhejiang University, Hangzhou 310027, China;MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China)

机构地区：[1]中国地震局地震预测研究所,北京100036 [2]中国地质大学(武汉)地球内部成像与探测实验室,武汉430074 [3]浙江大学地球科学学院,杭州310027 [4]华中科技大学物理学院基本物理量测量教育部重点实验室,武汉430074

出　　处：《地球物理学报》2018年第6期2380-2395,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41274142)资助

摘　　要：在高频面波方法中,水平分辨率是指水平方向上分辨异常体的能力.异常体在水平方向上的长度可用水平方向上横波速度的异常尺度来确定.面波多道分析(MASW)方法被广泛应用于浅地表横波速度结构的探测,然而该方法确定的横波速度是整个检波器排列的平均计算结果,因此水平分辨率较差.另外,采用共中心点(CMP)多次覆盖的方式采集数据亦增加了野外的工作量.我们在MASW方法的基础上,应用面波层析成像方法,提出一套提高面波勘探水平分辨率的完整方法的技术流程.首先,利用波场分离技术获得准确的基阶或高阶模式面波,采用相位扫描的互相关方法测量多道面波记录中任意两道之间的面波走时;然后根据面波层析成像方法,获得高分辨率的各目标网格内的纯路径相速度频散曲线;最后反演所有目标网格内的纯路径相速度频散曲线,得到研究区域的拟二维横波速度结构.这套方法具有一定的抗噪能力,理论上它可以准确地提取相邻两道之间面波的相速度频散曲线;同时由于该方法最少只需要1个排列就可以获得拟二维横波速度结构,因此它显著减小了野外工作量.理论模型和实际资料都证实了这套方法可有效提高面波勘探的水平分辨率.In high-frequency surface-wave methods,horizontal resolution refers to the ability to distinguish anomalous objects that are laterally displaced from each other.The horizontal length of a recognizable geological anomalous body is measured by the scale of shear（S）-wave velocityanomalies.The multichannel analysis of surface wave（MASW）method is an efficient tool to determine near-surface S-wave velocity.However the inverted 1 D S-wave velocity model is an averaged geophysical model under the receiver spread length,thus the MASW method has low horizontal resolution.In addition,the common middle point（CMP）roll-along acquisition method can increase the amount of fieldwork by the roll-along acquisition geometry.To solve these problems,on the basis of the MASW method,we propose a complete technique flow to improve horizontal resolution of surface-wave exploration by the travel-time tomography method.Firstly,we use the wave field separation technique to obtain accurate fundamental or higher mode of surface waves.And surface-wave phase-velocity dispersion curves between any two traces are calculated by the combined method of cross-correlation and phase-shift scanning from a multichannel record.Then with the application of travel-time tomography method,we obtain high resolution pure-path phase-velocity dispersion curves at diverse sizes of grids.Finally,the pseudo-2 D S-wave velocity structure is reconstructed by inverting pure-path phase-velocity dispersion curves.The proposed method can effectively enhance the ability of random noise immunity,and can extract accurate surface-wave phase-velocity dispersion curves from a record with a short receiver spacing theoretically.Moreover,the pseudo-2 DS-wave velocity structure can be obtained by the proposed method with at least only one seismic record,which reduces the amount of fieldwork dramatically.A synthetic test and a real-data example have demonstrated that the proposed method has a great potential in improving the horizontal resolution of surfacewave exploratio

关 键 词：水平分辨率 纯路径相速度频散曲线 面波层析成像方法 拟二维横波速度结构 

分 类 号：P631[天文地球—地质矿产勘探]