典型含煤模型Love型槽波的频散特征分析
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摘要
为了研究不同地质条件下煤层Love型槽波的频散特征,设计了4种典型二维地震地质模型,即围岩不变而煤厚变化(3,5,10,15和20 m)模型,围岩变化(高速围岩与低速围岩)而煤厚不变(10 m)模型,煤层含有断层(煤厚10 m、断层落差5 m)模型和10 m煤层中夹有5 m×5 m、5 m×10 m、5 m×20 m、5 m×50 m砂体模型等;采用SH波波动方程,对上述模型进行了数值模拟,分析了Love型槽波的波场特征,并对正演记录进行了傅里叶变换,计算得到槽波频散图。结果表明:煤厚变化主要影响Love型槽波各阶模式频散曲线的能量分布,上下围岩中最小横波速度控制频散曲线的上限,砂体使频散曲线发散,断层对槽波频散影响较小。
In order to study the dispersion characteristics of Love channel-waves under different geological conditions,four kinds models of 2D typical seismogeology were designed.There are various coal thickness models,different wall rock(high-velocity and low-velocity wall rock models)for which the coal thickness is stable as 10 m,coal models containing 5 m fault for which the coal thickness is 10 m,and coal imbedded by leat which sizes are 5 m×5 m,5 m×10 m,5 m×20 m and 5 m×50 m.These models were numerically simulated by SH wave equation.Analyzed the wave-fields characteristics of Love channel-waves and used Fourier transform on synthetic seismic records to obtain channel-waves dispersion curves;the results show that the coal thickness mainly influences energy distribution of different modes' dispersion curves.The minimum shear wave velocity between top and bottom wall rock controls upper limit of dispersion curves;leat bodies make dispersion curves diffuse.The fault has a low impact on channel-waves dispersion.
In order to study the dispersion characteristics of Love channel-waves under different geological conditions,four kinds models of 2D typical seismogeology were designed.There are various coal thickness models,different wall rock(high-velocity and low-velocity wall rock models)for which the coal thickness is stable as 10 m,coal models containing 5 m fault for which the coal thickness is 10 m,and coal imbedded by leat which sizes are 5 m×5 m,5 m×10 m,5 m×20 m and 5 m×50 m.These models were numerically simulated by SH wave equation.Analyzed the wave-fields characteristics of Love channel-waves and used Fourier transform on synthetic seismic records to obtain channel-waves dispersion curves;the results show that the coal thickness mainly influences energy distribution of different modes' dispersion curves.The minimum shear wave velocity between top and bottom wall rock controls upper limit of dispersion curves;leat bodies make dispersion curves diffuse.The fault has a low impact on channel-waves dispersion.
引文
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[14]Greenhaigf S A,King D W.Dispersive characteristic of Love-typechannel waves in Australian coal seams[J].Bull.Aust.Soc.Ex-plore.Geophys.,1981,12(1/2):5.
[15]Rader D,Schott W,Dresen L,et al.Calculation of dispersion curvesand amplitude-depth distributions of Love channel waves in hori-zontally-layered media[J].Geophysical Prospecting,1985,33:800-816.
[16]Buchanand J.Dispersion calculations for SH and P-SV waves inmultilayered coal seams[J].Geophysical Prospecting,1987,35:62-70.
[17]杨真,冯涛,Wang Shugang.0.9 m薄煤层SH型槽波频散特征及波形模式[J].地球物理学报,2010,53(2):442-449.Yang Zhen,Feng Tao,Wang Shugang.Dispersion characteristicsand wave shape mode of SH channel wave in a 0.9 m-thin coalseam[J].Chinese Journal of Geophysics,2010,53(2):442-449.
[2]Krey T C.Channel waves as a tool of applied geophysics in coal min-ing[J].Geophysics,1962,28:701-714.
[3]Mason I,Buchanan D,Booer A.Fault location by underground seis-mic survey[J].Institution of Electrical Engineers,1980,127:322-336.
[4]Buchanan D,Davis R,Jackson P,et al.Fault location by channelwave seismology in United Kingdom coal seams[J].Geophysics,1981,46:994-1002.
[5]Dresen L,Ruter H.Seismic coal exploration,part B:in-seam seismics[M].New York:Pergamon Press,1994.
[6]Ge M,Wang H,Hardy H R,et al.Void detection at an anthracitemine using an in-seam seismic method[J].International Journal ofCoal Geology,2008,73:201-212.
[7]刘天放,潘冬明,李德春,等.槽波地震勘探[M].徐州:中国矿业出版社,1994.
[8]Krey T C.Channel waves as a tool of applied geophysics in coal min-ing[J].Geophysics,1963,28:701-714.
[9]Asten M W,Drake L A,Edwards S.In-seam seismic Love wave scat-tering modeled by the Finite Element Method[J].Geophysical Pros-pecting,1984,32:649-661.
[10]Elsen R,Rueter H,Schott W.Seam waves along multilayered coalseams,some case histories[A].47th EAEG Meeting Budapest[C].1985.
[11]Liu E Crampins,Roth B.Modelling channel waves with syntheticseismograms in an anisotropic in-seam seismic survey[J].Geo-physical Prospecting,1991,40(5):513-540.
[12]潘冬明,刘天放.拉夫型槽波的有限差分合成[J].中国煤田地质,1990,2(2):54-59.Pan Dongming,Liu Tianfang.The finite difference synthetize ofLove channel-wave[J].Coal Geology of China,1990,2(2):54-59.
[13]朱光明,李桂花,程建远.煤矿巷道内地震勘探的数值模拟[J].煤炭学报,2008,33(11):1263-1267.Zhu Guangming,Li Guihua,Cheng Jianyuan.Numerical simulationof seismic survey in coal mine roadway[J].Journal of China CoalSociety,2008,33(11):1263-1267.
[14]Greenhaigf S A,King D W.Dispersive characteristic of Love-typechannel waves in Australian coal seams[J].Bull.Aust.Soc.Ex-plore.Geophys.,1981,12(1/2):5.
[15]Rader D,Schott W,Dresen L,et al.Calculation of dispersion curvesand amplitude-depth distributions of Love channel waves in hori-zontally-layered media[J].Geophysical Prospecting,1985,33:800-816.
[16]Buchanand J.Dispersion calculations for SH and P-SV waves inmultilayered coal seams[J].Geophysical Prospecting,1987,35:62-70.
[17]杨真,冯涛,Wang Shugang.0.9 m薄煤层SH型槽波频散特征及波形模式[J].地球物理学报,2010,53(2):442-449.Yang Zhen,Feng Tao,Wang Shugang.Dispersion characteristicsand wave shape mode of SH channel wave in a 0.9 m-thin coalseam[J].Chinese Journal of Geophysics,2010,53(2):442-449.
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