瞬变电磁拟地震子波宽度压缩研究
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摘要
导电媒质中电磁场所满足的扩散方程与无耗媒质中电磁场所满足的无阻尼波动方程之间存在着数学转换关系式,可以实现瞬变电磁法拟地震资料解释.但是转换出的虚拟波往往波形较宽,使分辨能力下降,影响了瞬变电磁拟地震方法的发展和推广,本文针对虚拟波形展宽这一现象进行了研究,认为虚拟波形展宽的原因,不是由于波在介质中传播时能量损耗所致,而是波场变换式中核函数随虚拟时间的增加,分布范围增大的特点导致的.然后提出利用反褶积技术,消除波场变换中的波形展宽效应.对已知模型的计算求解和处理,取得较好的效果.证明了瞬变电磁拟地震方法可以增强识别地下电性分界面的能力.
Because of the relationship between diffusion field of electromagnetic wave in conductive medium and electromagnetic wave equation in lossless medium,transient electromagnetic(TEM) method pseudo-seismic technology can be realized and wavelet can be transformed accordingly. But the transformed virtual wave is often with wide waveform,which reduces the resolution and affects the development and promotion of pseudo-seismic method.In this paper,we studied waveform broadening phenomena of virtual wave.Firstly,we discussed the reasons for virtual waveform broadening phenomena,pointed out that it is not due to the energy loss when wave propagates in the medium,but because that the propagation velocity of virtual wave in the virtual medium is much smaller than the velocity of electromagnetic wave propagating in the physical medium.Secondly,we put forward an idea that uses deconvolution technology to eliminate the waveform broadening effect in the wave-field transformation.We also computed and processed several known models and achieved good results which proved that the TEM method pseudoseismic technology can enhance the capacity of TEM method to identify the underground electrical interface so that makes the transient electromagnetic method in fine exploration possible.
Because of the relationship between diffusion field of electromagnetic wave in conductive medium and electromagnetic wave equation in lossless medium,transient electromagnetic(TEM) method pseudo-seismic technology can be realized and wavelet can be transformed accordingly. But the transformed virtual wave is often with wide waveform,which reduces the resolution and affects the development and promotion of pseudo-seismic method.In this paper,we studied waveform broadening phenomena of virtual wave.Firstly,we discussed the reasons for virtual waveform broadening phenomena,pointed out that it is not due to the energy loss when wave propagates in the medium,but because that the propagation velocity of virtual wave in the virtual medium is much smaller than the velocity of electromagnetic wave propagating in the physical medium.Secondly,we put forward an idea that uses deconvolution technology to eliminate the waveform broadening effect in the wave-field transformation.We also computed and processed several known models and achieved good results which proved that the TEM method pseudoseismic technology can enhance the capacity of TEM method to identify the underground electrical interface so that makes the transient electromagnetic method in fine exploration possible.
引文
[1] Auken E,Jorgensen F,Sorensen K I.Large-scale TEM investigation for ground-water.Exploration Geophysics ,2003,33:188～194
[2] Christensen N B,Sorensen K I.Surface and borehole electric and electromagnetic methods for hydrogeophysical investigations.European Journal of Environmental and Engineering Geophysics ,1998,3(1) :75～90
[3] Danielsen J E,Auken E,Jorgensen F,et al.The application of the transient electromagnetic method in hydrogeophysical surveys.Journal of Applied Geophysics ,2003,53:181～198
[4] Fitterman D V,Stewart M T.Transient electromagnetic sounding for groundwater.Geophysics,1986,51(4) :995～1005
[5] Jorgensen F,Sandersen P,Auken E .Imaging buried Quaternary valleys using the transient electromagnetic method.Journal of Applied Geophysics ,2003,53:199～ 213
[6] McNeill J D,Edwards R N,Levy G M.Approximate Calculation of the transient electromagnetic response from buried conductors in a conductive half-space.Geophysics,1984,49(7) :918～924
[7] Mgoldman the integralfinite Diffrence for calculation transient electromagnetic fields in Horizontally stratified medium.Geophysical Prospecting ,1983 ,31:664～686
[8] Wang T S,Hohmann G W,A finite differrence time domain solution for three-dimensional electromagnetic modeling.Geophysic,1993,58(6) t797~817
[9] Anderson W L.Numerical integration of related Hankel transforms of order O and 1 by adaptive digital filtering.Geophysics,1979,44(10) :1287～1305
[10] Spies B R.Depth of investigation in electromagnetic sounding methods.Geophysics,1989,54(7) :872～888
[11] Markku P,Saurabh K V,SvenErik Hjelt Inversion of transient electromagnetic profile data using conductive finite platemodel Journal of applied.Geophysics,1998,38:181～194
[12] Tartaras E,Zhdanov M S.Fast S-inversion in the time domain :method of interpretation using the thin sheet approach.66 Ann.Int.Mtg.,Soc.Expl Geophys.Expanded Abstract,1996． 1306～1309
[13] Zhdanov M S,Pavlov D A,Ellis R G.Localized S-inversion of time domain electromagnetic data.Geophysics,2002,67(4) .1115-1125
[14] Efthimios T,M ichael S Z,Kazushige W,Akira S.Fast imaging of TDEM data based on S-inversion.Journal of Applied Geophysics ,2000,43:15～32
[15] Liu G,Asten M.Conductance depth imaging of airborne TEM data.Exploration Geophysics ,1993,24:655～662
[16] Ben K Sternberg,James C Washburne,Louise Pellerin.Correction for the static shift in magnetotellurics using transient electromagnetic sounding.Geophysics,1988,53 (11) :1459～1468
[17] 薛国强,李貅,郭文波等.从瞬变电磁测深数据到平面电磁波场数据的等效转换.地球物理学报,2006,49(5) :1539～1545 Xue G Q ,Li X ,Guo W B ,et al.Equivalent transformation from TEM field sounding data to plane wave electromagnetic sounding data.Chinese J .Geophys.(in Chinese),2006,49 (5) :1539～1545
[18] Lee K H.Liu G,Morrison H F.A new approach to modeling the electromagnetic response of conductive media.Geophysics,1989 ,54(6) :1180～1192
[19] Mier Genshenson.Simple interpretation of time-domain electromagnetic sounding using similarities between wave and diffusion propagation.Geophysics,1993,62(3) :763～774
[20] Lee H K,Xie A.A new approach to imaging with lowfrequency electromagnetic.Geophysics,1993 ,58 (6) :780～786
[21] Gershenson.Simple interpretation of time domain electromagnetic sounding using similarities between wave and diffusion propagation.Geophysics,1997,62(3) :763～777
[22] Tae J,Jung H S,Hee J K,et al.Electromagnetic travel time tomography using approbobiHty wave-field transform.Geophysics,2002,67(3) :67~69
[23] Zhdanov M S,Portniaguine O.Time-domain electromagnetic migration in the solution of inverse problems.Geophysics,1997 ,62(2) t293~309
[24] 李貅,薛国强,宋建平等.从瞬变电磁场到波场的优化算法.地球物理学报,2005,48(5) :1185～1190 Li X,Xue G Q,Song J P,et al.An optimize method for transient electromagnetic field-wave field conversion.Chinese J.Geophys.(in Chinese) ,2005 ,48(5) :1185～1190
[25] Xue G Q,Yan Y J,Li X.Pseudo-Seismic Wavelet transformation of transient electromagnetic response in geophysical exploration.Journal of Geophysical Research Letters,34,L16405,doi:10． 1029/2007 GL031116,2007
[26] Peacock K L,Treitel S.Predictive deconvolution-Theory and practices.Geophysics,1969,34(2) :155～169
[2] Christensen N B,Sorensen K I.Surface and borehole electric and electromagnetic methods for hydrogeophysical investigations.European Journal of Environmental and Engineering Geophysics ,1998,3(1) :75～90
[3] Danielsen J E,Auken E,Jorgensen F,et al.The application of the transient electromagnetic method in hydrogeophysical surveys.Journal of Applied Geophysics ,2003,53:181～198
[4] Fitterman D V,Stewart M T.Transient electromagnetic sounding for groundwater.Geophysics,1986,51(4) :995～1005
[5] Jorgensen F,Sandersen P,Auken E .Imaging buried Quaternary valleys using the transient electromagnetic method.Journal of Applied Geophysics ,2003,53:199～ 213
[6] McNeill J D,Edwards R N,Levy G M.Approximate Calculation of the transient electromagnetic response from buried conductors in a conductive half-space.Geophysics,1984,49(7) :918～924
[7] Mgoldman the integralfinite Diffrence for calculation transient electromagnetic fields in Horizontally stratified medium.Geophysical Prospecting ,1983 ,31:664～686
[8] Wang T S,Hohmann G W,A finite differrence time domain solution for three-dimensional electromagnetic modeling.Geophysic,1993,58(6) t797~817
[9] Anderson W L.Numerical integration of related Hankel transforms of order O and 1 by adaptive digital filtering.Geophysics,1979,44(10) :1287～1305
[10] Spies B R.Depth of investigation in electromagnetic sounding methods.Geophysics,1989,54(7) :872～888
[11] Markku P,Saurabh K V,SvenErik Hjelt Inversion of transient electromagnetic profile data using conductive finite platemodel Journal of applied.Geophysics,1998,38:181～194
[12] Tartaras E,Zhdanov M S.Fast S-inversion in the time domain :method of interpretation using the thin sheet approach.66 Ann.Int.Mtg.,Soc.Expl Geophys.Expanded Abstract,1996． 1306～1309
[13] Zhdanov M S,Pavlov D A,Ellis R G.Localized S-inversion of time domain electromagnetic data.Geophysics,2002,67(4) .1115-1125
[14] Efthimios T,M ichael S Z,Kazushige W,Akira S.Fast imaging of TDEM data based on S-inversion.Journal of Applied Geophysics ,2000,43:15～32
[15] Liu G,Asten M.Conductance depth imaging of airborne TEM data.Exploration Geophysics ,1993,24:655～662
[16] Ben K Sternberg,James C Washburne,Louise Pellerin.Correction for the static shift in magnetotellurics using transient electromagnetic sounding.Geophysics,1988,53 (11) :1459～1468
[17] 薛国强,李貅,郭文波等.从瞬变电磁测深数据到平面电磁波场数据的等效转换.地球物理学报,2006,49(5) :1539～1545 Xue G Q ,Li X ,Guo W B ,et al.Equivalent transformation from TEM field sounding data to plane wave electromagnetic sounding data.Chinese J .Geophys.(in Chinese),2006,49 (5) :1539～1545
[18] Lee K H.Liu G,Morrison H F.A new approach to modeling the electromagnetic response of conductive media.Geophysics,1989 ,54(6) :1180～1192
[19] Mier Genshenson.Simple interpretation of time-domain electromagnetic sounding using similarities between wave and diffusion propagation.Geophysics,1993,62(3) :763～774
[20] Lee H K,Xie A.A new approach to imaging with lowfrequency electromagnetic.Geophysics,1993 ,58 (6) :780～786
[21] Gershenson.Simple interpretation of time domain electromagnetic sounding using similarities between wave and diffusion propagation.Geophysics,1997,62(3) :763～777
[22] Tae J,Jung H S,Hee J K,et al.Electromagnetic travel time tomography using approbobiHty wave-field transform.Geophysics,2002,67(3) :67~69
[23] Zhdanov M S,Portniaguine O.Time-domain electromagnetic migration in the solution of inverse problems.Geophysics,1997 ,62(2) t293~309
[24] 李貅,薛国强,宋建平等.从瞬变电磁场到波场的优化算法.地球物理学报,2005,48(5) :1185～1190 Li X,Xue G Q,Song J P,et al.An optimize method for transient electromagnetic field-wave field conversion.Chinese J.Geophys.(in Chinese) ,2005 ,48(5) :1185～1190
[25] Xue G Q,Yan Y J,Li X.Pseudo-Seismic Wavelet transformation of transient electromagnetic response in geophysical exploration.Journal of Geophysical Research Letters,34,L16405,doi:10． 1029/2007 GL031116,2007
[26] Peacock K L,Treitel S.Predictive deconvolution-Theory and practices.Geophysics,1969,34(2) :155～169
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