τ-p变换在隧道地震超前探测中的应用及适应性分析
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摘要
TETSP-2隧道地震超前探测系统利用三分量检波器接收地震信号,迫切需要将数据中的纵横波信息分离。文章由隧道内线性观测系统的反射纵横波时距曲线进行推导,并基于Taylor理论分析τ-p变换在隧道地震超前探测中的物理意义和可行性,给出τ-p变换截距和慢度与反射界面倾角的关系,模拟简单条件下二维隧道空间内的地震全波场,分析不同波场的反射特征,比较不同倾角情况下反射纵横波在τ-p变换域中的特征及差异。结果表明:不同倾角反射纵横波的视速度不同,随着倾角逐渐变小,视速度变大。τ-p变换能够利用视速度差异进行波场分离,在隧道前方低速带倾角较大时(40°以上),分离效果较好;在倾角较小时,时距曲线的一阶Taylor展开式具有较大误差,分离效果变差。
As a result of the use of a three-component geophone to receive seismic signals in TETSP-2 tunnel seismic advance detection system; it is urgent to separate the mixed information such as primary wave and secondary wave in seismic wavefield. In this paper,the time-distance curve of the reflected longitudinal and transverse wave in the tunnel is deduced; the applicability of the τ-p transform in the tunnel seismic advance detection is theoretically analyzed based on Taylor's formula; and the relationships between nodal increment and slowness of τ-p transform and reflection interface dip angle are given. And then the whole wavefield in the two-dimensional tunnel space under simple conditions is simulated; the reflection characteristics of different wavefields are analyzed; and the characteristics and differences of reflection P-wave and S-wave in τ-p transform domain are compared under different dip angles. The results show that:(1) The apparent velocity of reflection transverse wave under different dip angles varies,and the apparent velocity increases with dip angle decrease.(2) The τ-p transform can separate wavefield relying on different apparent velocity between primary wave and secondary wave; the method can well separate the wavefield when the dip angle of low speed zone in front of tunnel face is no less than 40°; but when the dip angle is small,the first-order Taylor expansion of timedistance curve has a large error,which makes the effect of wavefield separation bad.
As a result of the use of a three-component geophone to receive seismic signals in TETSP-2 tunnel seismic advance detection system; it is urgent to separate the mixed information such as primary wave and secondary wave in seismic wavefield. In this paper,the time-distance curve of the reflected longitudinal and transverse wave in the tunnel is deduced; the applicability of the τ-p transform in the tunnel seismic advance detection is theoretically analyzed based on Taylor's formula; and the relationships between nodal increment and slowness of τ-p transform and reflection interface dip angle are given. And then the whole wavefield in the two-dimensional tunnel space under simple conditions is simulated; the reflection characteristics of different wavefields are analyzed; and the characteristics and differences of reflection P-wave and S-wave in τ-p transform domain are compared under different dip angles. The results show that:(1) The apparent velocity of reflection transverse wave under different dip angles varies,and the apparent velocity increases with dip angle decrease.(2) The τ-p transform can separate wavefield relying on different apparent velocity between primary wave and secondary wave; the method can well separate the wavefield when the dip angle of low speed zone in front of tunnel face is no less than 40°; but when the dip angle is small,the first-order Taylor expansion of timedistance curve has a large error,which makes the effect of wavefield separation bad.
引文
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[2]姜天平.多道中值滤波在分离VSP波场中的应用[J].石油地球物理勘探,1985,20(4):433.JIANG Tianping.Median filtering applied to separation of VSP wave field[J].Oil Geophysical Prospecting,1985,20(4):433.
[3]高磊,陈文超,王保利,等.基于两步SVD变换的零偏VSP资料上下行波场分离方法[J].地球物理学报,2013,56(5):1667.GAO Lei,CHEN Wenchao,WANG Baoli,et al.Zero-offset VSP wavefield separation using two-step SVD approach[J].Chinese Journal of Geophysics,2013,56(5):1667.
[4]单波,张玉芬.瞬时极化滤波在波场分离中的应用[J].物探化探计算技术,2009,31(5):494.SHAN Bo,ZHANG Yufen.Application of instantaneous polarization filter in wave-field separation[J].Computing Techniques for Geophysical and Geochemical Exploration,2009,31(5):494.
[5]罗省贤,李录明.F-K域多波变速波场分离[J].物探化探计算技术,1999,21(2):31.LUO Shengxian,LI Luming.Multi-wave field decomposition by the variable velocity method in F-K domain[J].Computing Techniques for Geophysical and Geochemical Exploration,1999,21(2):31.
[6]王维红,首皓,刘洪,等.线性同相轴波场分离的高分辨率τ-p变换法[J].地球物理学进展,2006,21(1):74.WANG Weihong,SHOU Hao,LIU Hong,et al.High resolutionτ-p transform in linear events wavefield separation[J].Progress in Geophysics,2006,21(1):74.
[7]沈鸿雁,李庆春.奇异值分解(SVD)实现地震波场分离与去噪新思路[J].地球物理学进展,2010,25(1):225.SHEN Hongyan,LI Qingchun.New idea for seismic wave filed separation an denoising by singular value decomposition(SVD)[J].Progress in Geophysics,2010,25(1):225.
[8]沈鸿雁,李庆春,冯宏,等.反射波法隧道、井巷地震超前探测中波场分离与成像技术研究[C]//中国地球物理学会第22届年会论文集.成都:四川科学技术出版社,2006:672.SHEN Hongyan,LI Qinchun,FENG Hong,et al.Study of wave filed separation image technology in tunnel and laneway advance detection with reflected-wave method[C]//22nd Annual Proceedings of Chinese Geophysical Society Conference.Chengdu:Sichuan Science and Technology Publishing House,2006:672.
[9]王朝令,刘争平,黄云艳,等.F-K变换在隧道反射地震预报波场分离中的数值模拟研究[J].大地测量与地球动力学,2014,34(4):71.WANG Zhaoling,LIU Zhengping,HUANG Yunyan,et al.Modeling research of F-K transform applied in the tunnel earthquake prediction[J].Journal of Geodesy and Geodynamics,2014,34(4):71.
[10]王朝令,刘争平.τ-p变换在隧道反射地震超前预报波场分离中应用的数值模拟研究[J].地球物理学进展,2012,27(5):2216.WANG Zhaoling,LIU Zhengping.The modelling study ofτ-p transform applied in the tunnel seismic prediction[J].Progress in Geophysics,2012,27(5):2216.
[11]葛文,张致付,李永军.自适应极化滤波在地震超前探测波场分离中的应用[J].地球物理学进展,2016,31(2):649.GE Wen,ZHANG Zhifu,LI Yongjun.Application of adaptive polarization filter to wave separation in tunnel seismic prediction data processing[J].Progress in Geophysics,2016,31(2):649.
[12]HELGASON S.The Radon transform[M].[S.l.]:Birkhhauser,1999.
[13]曾有良,乐友喜,单启铜,等.基于高分辨率Radon变换的VSP波场分离方法[J].石油物探,2007,46(2):115.ZENG Youliang,YUE Youxi,SHAN Qitong,et al.VSP wave field separation based on high-resolution Radon transformation[J].Geophysical Prospecting for Petroleum,2007,46(2):115.