可控震源非线性扫描地震响应的数值模拟
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摘要
讨论了几种非线性扫描信号自相关函数的旁瓣特性.对可控震源非线性扫描的地震响应进行了数值模拟.当震源扫描持续时间是检波器接收时间的一半时,相关运算把反射扫描信号压缩成脉冲信号的效果是显著的.有限度地增加震源扫描持续时间以及与之相适应的接收时间可以使反射扫描信号得到进一步的压缩,但在固定扫描与接收时间的条件下,增加采样点个数对反射扫描信号的压缩并不起作用.采用具有低频相关子波特性的非线性扫描震源信号,将有利于相关噪声的消除.模拟结果还证实了二次扫描在某些特定条件下会出现鞍点效应这样一个事实.
We discuss the properties of the side lobes of autocorrelation functions for several nonlinear sweeping signals and perform the numerical simulation for seismic response to the nonlinear sweeping signal produced by a vibrator.On condition that the sweeping duration is round about half the receiving time of geophones,the effect of compressing reflective sweep signals into pulse signals with the correlation operation is very remarkable.Increasing sweeping duration and receiving duration within limits,reflective sweep signals can be further compressed.But increasing samples with invariable sweeping duration and receiving duration is not helpful to compress those.Employing the nonlinear sweep signals with the properties of low frequency correlation wavelet will be benefit to the elimination of the correlation noises.The simulation results also show that a saddle point effect will appear for the quadratic sweeping at some special conditions.
We discuss the properties of the side lobes of autocorrelation functions for several nonlinear sweeping signals and perform the numerical simulation for seismic response to the nonlinear sweeping signal produced by a vibrator.On condition that the sweeping duration is round about half the receiving time of geophones,the effect of compressing reflective sweep signals into pulse signals with the correlation operation is very remarkable.Increasing sweeping duration and receiving duration within limits,reflective sweep signals can be further compressed.But increasing samples with invariable sweeping duration and receiving duration is not helpful to compress those.Employing the nonlinear sweep signals with the properties of low frequency correlation wavelet will be benefit to the elimination of the correlation noises.The simulation results also show that a saddle point effect will appear for the quadratic sweeping at some special conditions.
引文
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[15]Zhang J F.Elastic wave modelling in heterogeneous mediawith high velocity contrasts[J].Geophysical Journal Interna-tional.2004,159(1):223~239.
[16]王德利,何樵登,韩立国.裂隙型单斜介质中多方位地面三分量记录模拟[J].地球物理学报,2005,48(2):386~393.
[17]郑海山,张中杰.横向各向同性(VTI)介质中非线性地震波场模拟[J].地球物理学报,2005,48(3):660~671.
[2]林君,陈鹏程,姜弢,等.浅层地震勘探的可控震源信号设计[J].地球物理学进展,2004,19(4):807~811.
[3]Werner H,Krey T H.Combisweep-A Contribution to SweepTechniques[J].Geophysical Prospecting,1979,27:78~105.
[4]Cunningham A B.Some Alternate Vibrator Signals[J].Geo-physics,1979,44(12):1901~1921.
[5]Becquey M,Bianchi T and Meunier J.Pseudo-random codedsimultaneous vibroseismics.SEG Annual Meeting ExpandedTechnical Program Abstracts with Biographies.72;Pages 77~80.2002.
[6]Goupillaud P L.Signal Design in the“Vibroseis”Technique[J].Geophysics,1976,41(6):1291~1304.
[7]Carcione J M.Seismic Modeling in Viscoelastic Media[J].Ge-ophysics,1993,58(1):110~120.
[8]罗明秋,刘洪,李幼铭.适用于波场成像的谱法LU分解[J].地球物理学报,2003,46(3):421~427.
[9]王秀明,张海澜,王东.利用高阶交错网格有限差分法模拟地震波在非均匀孔隙介质中的传播[J].地球物理学报,2003,46(6):842~849.
[10]Yang D H,Wang S Q,Zhang Z J,Teng J W.n-Times ab-sorbing boundary conditions for compact finite-differencemodeling of acoustic and elastic wave propagation in the 2DTI medium[J].Bulletin of the Seismological Society of Amer-ica,2003,93(6):2389~2401.
[11]夏凡,董良国,马在田.三维弹性波数值模拟中的吸收边界条件[J].地球物理学报,2004,47(1):132~136.
[12]孙卫涛,杨慧珠.各向异性介质弹性波传播的三维不规则网格有限差分法[J].地球物理学报,2004,47(2):332~337.
[13]崔兴福,张关泉,吴雅丽.三维非均匀介质中真振幅地震偏移算子研究[J].地球物理学报,2004,47(3):509~513.
[14]刘礼农,崔凤林,张剑锋.三维复杂构造中地震波模拟的单程波方法[J].地球物理学报,2004,47(3):514~520.
[15]Zhang J F.Elastic wave modelling in heterogeneous mediawith high velocity contrasts[J].Geophysical Journal Interna-tional.2004,159(1):223~239.
[16]王德利,何樵登,韩立国.裂隙型单斜介质中多方位地面三分量记录模拟[J].地球物理学报,2005,48(2):386~393.
[17]郑海山,张中杰.横向各向同性(VTI)介质中非线性地震波场模拟[J].地球物理学报,2005,48(3):660~671.
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