震源深度对低速带区地震波传播特征的影响
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摘要
采用声波波动方程数值模拟方法,对在不同震源深度情况下地震波场在低速带中的传播特征进行了模拟与分析。数值模拟结果表明,当震源位于地表时,会产生多次折射波;当炮点位于低速带内时,在产生折射波的同时,还会产生较强的虚反射,使波场变得更加复杂;当炮点位于低速带以下时,一次反射波的信噪比最高。在野外生产中,震源放在低速带以下有利于提高一次反射波的品质。如果条件允许,最好将检波器也埋置到低速带以下。
A method for numerical simulation of acoustic wave equation is used to simulate and analyze the characteristics of weathering propagation in seismic field for different source depthes. The simulated result shows that when the source is at the surface, it will produce a multiple refracted wave; when the shot point is located in the weathering area, it will produce stronger ghost reflection while producing refracted waves, so as to make the wave field more complicated; when the shot point is under the weathering, the signal noise-ratio is the highest in the first reflection wave. In the field production, the source beneath the weathering is beneficial for improving the quality of first reflection wave. If the condition is allowable, the best way is to bury the geophone beneath the weathering belt.
A method for numerical simulation of acoustic wave equation is used to simulate and analyze the characteristics of weathering propagation in seismic field for different source depthes. The simulated result shows that when the source is at the surface, it will produce a multiple refracted wave; when the shot point is located in the weathering area, it will produce stronger ghost reflection while producing refracted waves, so as to make the wave field more complicated; when the shot point is under the weathering, the signal noise-ratio is the highest in the first reflection wave. In the field production, the source beneath the weathering is beneficial for improving the quality of first reflection wave. If the condition is allowable, the best way is to bury the geophone beneath the weathering belt.
引文
[1]Sheriff R E·Exploration seismology[M]·London:Cambridge University Press,1995·
[2]Cerjan C,Kosloff D·Anonreflecting boundary condition for discrete acoustic and elastic wave equation[J]·Geophysics,1985,50(4):705~708·
[3]Kelly K R,Ward R W·Synthetic seismograms:a finite-difference approach[J]·World Oil,1976,41(1):2~27·
[4]范祯祥,郑仙种·地震波数值模拟与偏移成像[M]·郑州:河南科学技术出版社,1994·
[2]Cerjan C,Kosloff D·Anonreflecting boundary condition for discrete acoustic and elastic wave equation[J]·Geophysics,1985,50(4):705~708·
[3]Kelly K R,Ward R W·Synthetic seismograms:a finite-difference approach[J]·World Oil,1976,41(1):2~27·
[4]范祯祥,郑仙种·地震波数值模拟与偏移成像[M]·郑州:河南科学技术出版社,1994·
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