【摘要】 本文在不考虑地震波吸收和几何扩散衰减的情况下,利用单频谐和平面纵波垂直入射到煤层上,来研究煤层的调频效应,正演模拟地震波的频率与反射系数的关系,分析了频率对反射系数的影响.研究表明:当地下只有一组煤时,在中高频段煤层反射系数较大,当存在两组煤或是更多组煤层时,受上组煤层的屏蔽,下组煤在低频段的反射系数明显大于中高频段的反射系数,从而为克服上组煤层的屏蔽,得到好的下组煤层反射波提供了理论基础.在此基础上提出了提高下组煤反射波质量的采集方案.由于历史的原因,煤田勘探一般使用中高频检波器(主频60 Hz或是100 Hz),虽然有利于提高中高频反射波的能量,但牺牲了信号的低频部分,不利于提高反射波的分辨率,同时损失了下组煤层中起主要作用的低频反射波,得到的下组煤反射波资料一般很差.更多还原

【Abstract】 This paper analyses how frequency affects reflectance by using the single frequency surface compressional wave that is vertically incident without taking the absorbing and diffusing in account to research the coal seam’s frequency modulation effect.It is concluded that when there is only one layer,the coal reflectance is large in the mid-high frequency domain,but the down coal seam’s reflectance is bigger in the low frequency than in the mid-high frequency when the two-layer-coal seams or more exist because of the up coal seam’s shielding.So it provides the theorical base to overcome the up coal seam’s shielding.Based upon this result,a method advancing the down coal seam is suggested.Due to the historical reason,explorations of coalfields usually apply the high frequency receivers. It kills the low frequency component which is bad to the resolution,as well as the low frequency reflection that is dominating to the down coal seam though it enhances the energy in the mid-high frequency domain.更多还原