平面波在粘滞性界面上的反射特征研究
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摘要
当介质中存在按照一定方向排列的裂隙时,会在该区域形成接触程度不好的界面.当有地震波传播时,界面两侧的质点不再满足位移连续的条件,位移差与该点的应力有关.从而引起质点间的滑动,形成粘滞性界面.界面的这种特性可以用切向柔量和法向柔量来表示,柔量值越大,界面的接触程度和质点位移的连续性都越差.文中详细推导了平面波在粘滞性界面上的反射和透射系数公式,通过数值算例证明了粘滞性界面上的反射系数与入射波频率有关的性质.并说明了界面的粘滞性会在一定程度上影响到反射波的AVO特性.且当平面P波入射时,法向柔量对反射P波和转换波的影响均大于切向柔量的影响.
Imperfectly bonded interfaces maybe exist with some aligned cracks in the media.Displacement across this interface is not required to be continuous as seismic waves propagating through this region.The displacement discontinuity is taken to be related to the stress across the interface,which cause the adjacent particles slip and form a visco-interface.This behavior can be expressed by two compliances,shear compliance and normal compliance.With the increasing of interface compliances,the bonding level becomes poorer and the displacement error becomes larger.Reflection and transmission equations of planar waves incident to such interfaces are deduced in detail in this paper.Through some numerical examples,the property that reflections and transmissions from visco-interface are related to frequency is emphasized.Also,the viscosity can affect AVO characters of the reflection waves to some extent.It is showed that the normal compliance has much influence on P-P and P-S reflections than that shear compliance do when the incident wave is P-wave.
Imperfectly bonded interfaces maybe exist with some aligned cracks in the media.Displacement across this interface is not required to be continuous as seismic waves propagating through this region.The displacement discontinuity is taken to be related to the stress across the interface,which cause the adjacent particles slip and form a visco-interface.This behavior can be expressed by two compliances,shear compliance and normal compliance.With the increasing of interface compliances,the bonding level becomes poorer and the displacement error becomes larger.Reflection and transmission equations of planar waves incident to such interfaces are deduced in detail in this paper.Through some numerical examples,the property that reflections and transmissions from visco-interface are related to frequency is emphasized.Also,the viscosity can affect AVO characters of the reflection waves to some extent.It is showed that the normal compliance has much influence on P-P and P-S reflections than that shear compliance do when the incident wave is P-wave.
引文
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[2]孙成禹,杜世通.平面声波在粗糙界面上的反射特征研究[J].地球物理学报,2006,49(3):903~907.Sun C Y,Du S T.Reflection features of planar acousticwaves from rough interfaces[J].Chinese J.Geophys.(InChinese),2006,49(3):903~907.
[3]孙成禹.粗糙界面地震反射波场的滤波特性[J].石油地球物理勘探,2004,39(1):24~28.Sun C Y.Filtering features of seismic reflection wavefield oncoarse interfaces[J].Oil Geophysical Prospecting(InChinese),2004,39(1):24~28.
[4]孙成禹.过渡层反射特征及脉冲波的振幅调谐现象[J].石油物探,2001,40(3):1~7,49.Sun C Y.Reflection signatures of transitional layer and itstuning effects to the amplitudes of pulsating waves[J].Geo-physical prospecting for petroleum(In Chinese),2001,40(3):1~7,49.
[5]宋景唯.随机粗糙表面电磁散射的仿真研究[J].地球物理学报,1994,37(增刊1):57~63.Song J W.Simulation of EM wave scatering from 3D randomrough surface[J].Acta Geophysica Sinia(In Chinese),1994,37(Supp.1):57~63.
[6]Schoengerg M.Elastic wave behavior across linear slip inter-faces[J].J.Acoust.Soc.Am,1980,68(5):1516~1521.
[7]Schoengerg M.Reflection of elastic waves from periodicallystratified media with interfacial slip[J].Geophysical Prospec-ting,1983,31,265~292.
[8]刘恩儒,岳建华,刘彦.具有离散裂缝空间分布的二维固体中地震波传播的有限差分模拟[J].地球物理学报,2006,49(1):180~188.Liu E R,Yue J H,Liu Y.Finite difference simulation ofseismic wave propagation in 2-D solids with spatial distributionof discrete fractures[J].Chinese J.Geophys.(in Chinese),2006,49(1):180~188.
[9]刘恩儒,岳建华,潘冬明.地震各向异性--多组裂隙对横波偏振的影响[J].地球物理学报,2006,49(5):1401~1409.Liu E R,Yue J H,Pan D M.Frequency-dependent anisotro-py:Effects of multiple fracture sets on shear-wave polariza-tions[J].Chinese J.Geophys.(in Chinese),2006,49(5):1401~1409.
[10]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.Zheng H S,Zhang Z J.Synthetic seismograms of nonlinearseismic waves in anisotropic(VTI)media[J].Chinese J.Geophys.(in Chinese),2005,48(3):660~671.
[11]张中杰.地震各向异性研究进展[J].地球物理学进展,2002,17(2):281~293.Zhang Z J.A Review of the Seismic anisotropy and its appli-cations[J].Progress in geophysics(In Chinese),2002,17(2):281~293.
[12]何芳社,黄义.横观各向同性饱和土的基本方程组[J].地球物理学报,2007,50(1):131~137.He F S,Huang Y.Basic equations of transversely isotropicfluid-saturated poroelastic media[J].Chinese J.Geophys.(in Chinese),2007,50(1):131~137.
[13]Murty G S,Kumar V.Elastic wave propagation with kine-matic discontinuity along a non-ideal interface between two i-sotropic elastichalf-spaces[J].J Nondestr Eval,1991,10(2):39~53.
[14]Bostrom A,Wickham G.On the boundary conditions for ul-trosonic transmission by partially closed crack[J].J NondestrEval,1991,10(4):139~149.
[15]Margetan F J,Thompson R B,Rose J H,Gray T A.The in-teraction of ultrosound with imperfect interfaces:experimen-tal studies of model structures[J].J.Nondestr.Eval.,1992,11(3/4):109~126.
[16]汪越胜,于桂兰,章梓茂,冯仰德.复杂界面(界面层)条件下的弹性波传播问题研究综述[J].力学进展,2000,30(3):378~390.Wang Y S,Yu G L,Zhang Z M,Feng Y D.Review on elas-tic wave propagation under complex interface(interface layer)conditions[J].Advances in mechanics(In Chinese),2000,30(3):378~390.
[17]余湘彬,仲政,文洁.滑动界面球形夹杂对平面压缩波的散射[J].力学季刊,2000,21(2):173~178.Yu X B,Zhong Z,Wen J.Scattering of plane compressionalwaves by a sliding spherical inhomogeneity[J].ChineseQuarterly of Mechanics(In Chinese),2000,21(2):173~178.
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