折射初至波射线追踪方法研究
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摘要
在复杂地表区采用传统的射线追踪算法得到的近地表速度结构与微测井测量结果偏差较大,造成这种情况的主要原因是求取射线路径的精度较低。采用常规的基于旅行时平方的非线性插值法虽然提高了射线路径和旅行时间的计算精度,但是不适用于速度变化剧烈地区。本文在分析此类非线性插值法误差来源的基础上对该方法进行改进,在充分考虑各种可能射线路径的基础上,采用非线性旅行时插值方法计算地震初至波的射线路径和旅行时。数值计算结果表明:本方法在保证地震波旅行时计算精度的前提下,可以采用较粗的计算网格提高射线追踪的效率,并能够适应各种复杂的速度结构。
There is large difference in near-surface velocity structure between the results of uphole survey and traditional ray-tracing algorithm in complex surface area, the main reason of which is lower precision of computed ray path. The traditional non-linear interpolation based on travel-time square although improved the computational precision of ray path and travel time, the algorithm is not suitable for the area the velocity violently changed. Based on analyzing the error source of this kind of non-linear interpolation, the paper improved the algorithm, using non-linear travel-time interpolation to compute ray path and travel time of seismic first breaks on the basis of fully considering various possible ray paths. The numeric computational results showed that the approach can use sparse computational grid in a precondition of guaranteeing computational precision of seismic travel times, improving efficiency of ray tracing and can suitable for various complex velocity structures.
There is large difference in near-surface velocity structure between the results of uphole survey and traditional ray-tracing algorithm in complex surface area, the main reason of which is lower precision of computed ray path. The traditional non-linear interpolation based on travel-time square although improved the computational precision of ray path and travel time, the algorithm is not suitable for the area the velocity violently changed. Based on analyzing the error source of this kind of non-linear interpolation, the paper improved the algorithm, using non-linear travel-time interpolation to compute ray path and travel time of seismic first breaks on the basis of fully considering various possible ray paths. The numeric computational results showed that the approach can use sparse computational grid in a precondition of guaranteeing computational precision of seismic travel times, improving efficiency of ray tracing and can suitable for various complex velocity structures.
引文
[1]张建中.近地表介质地震初至波层析成像.厦门大学学报(自然科学版),2004,43(1):63~66
[2]林伯香,孙晶梅,刘清林.层析成像低速带速度反演和静校正方法.石油物探,2002,41(2):136~140
[3]Julian B R,Gubbins D.Three-di mensional seismic ray tracing.Geophys,1977,43(1):95~114
[4]Um J,Thurber C.A fast algorithm for two point seismic ray tracing.Bulletin of the Seismological Society of America,1987,77(3):972~986
[5]Vidale J.Finite-difference calculation of travel ti mes.Bulletin of the Seismological Society of America,1988,78(6):2062~2076
[6]Van Trier J,Symes W.Upwind finite-difference cal-culation of travel ti mes.Geophysics,1991,56(6):812~821
[7]Qin F,Olsen K B,Cai W,Schuster G T.Finite-differ-ence solution of the eikonal equation along expanding wavefronts.Geophysics,1992,57(3):478~487
[8]Asakawa E,Kawanaka T.Seismic ray tracing using linear travel ti meinterpolation.Geophysical Prospec-ting,1993,1(1):99~111
[9]Vidale J E.Finite-difference calculation of travel ti mes in three di mensions.Geophysics,1990,55(5):521~526
[10]聂建新,杨慧珠.地震波旅行时二次/线性联合插值法.清华大学学报(自然科学版),2003,43(11):1495~1498
[11]彭直兴,张芬,周熙襄等.地震波旅行时非线性/线性联合插值法.成都理工大学学报(自然科学版),2005,32(3):322~324
[12]张建中,陈世军,余大祥.最短路径射线追踪方法及其改进.地球物理学进展,2003,18(1):146~150
[2]林伯香,孙晶梅,刘清林.层析成像低速带速度反演和静校正方法.石油物探,2002,41(2):136~140
[3]Julian B R,Gubbins D.Three-di mensional seismic ray tracing.Geophys,1977,43(1):95~114
[4]Um J,Thurber C.A fast algorithm for two point seismic ray tracing.Bulletin of the Seismological Society of America,1987,77(3):972~986
[5]Vidale J.Finite-difference calculation of travel ti mes.Bulletin of the Seismological Society of America,1988,78(6):2062~2076
[6]Van Trier J,Symes W.Upwind finite-difference cal-culation of travel ti mes.Geophysics,1991,56(6):812~821
[7]Qin F,Olsen K B,Cai W,Schuster G T.Finite-differ-ence solution of the eikonal equation along expanding wavefronts.Geophysics,1992,57(3):478~487
[8]Asakawa E,Kawanaka T.Seismic ray tracing using linear travel ti meinterpolation.Geophysical Prospec-ting,1993,1(1):99~111
[9]Vidale J E.Finite-difference calculation of travel ti mes in three di mensions.Geophysics,1990,55(5):521~526
[10]聂建新,杨慧珠.地震波旅行时二次/线性联合插值法.清华大学学报(自然科学版),2003,43(11):1495~1498
[11]彭直兴,张芬,周熙襄等.地震波旅行时非线性/线性联合插值法.成都理工大学学报(自然科学版),2005,32(3):322~324
[12]张建中,陈世军,余大祥.最短路径射线追踪方法及其改进.地球物理学进展,2003,18(1):146~150
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