【作者】 姚振兴； 徐大方；

【Author】 Yao Zhenxing Xu Dafang (Institute of Geophysics,Chinese Academy of Sciences)

【机构】 中国科学院地球物理研究所；

【摘要】 实现横波(SH波)勘探的关键问题是震源,现有的SH波震源——扭力振动器的缺点是辐射方向性不好,能量集中在水平方向,而在垂直方向辐射的能量几乎为零,这样的震源对于反射波勘探是不利的。本文从理论上提出用垂直力矩构成横波震源。理论推导结果(高频渐近解)表明,该震源在方位角θ=90°方向上辐射纯SH波,且辐射能量主要集中在垂直方向,而在水平方向几乎为零。显然,这样的震源对于反射波勘探十分有利。文中还采用Cagniard-deHoop回路积分技术计算了波场的精确解及最大振幅随离源角的变化,结果与解析解一致。更多还原

【Abstract】 A seismic source that produces nearly pure SH-waves is important for shear wave prospecting. A disadvantage of the torsional vibrator which can generate pure SH-waves is the directional characteristic:the radiation of seismic energy is concentrated at shallow angle,but the emission in vertical direction is nearly zero.It is obvious that such a source is not favourable for reflection prospecting. A new shear wave source constructed by a vertical dipole is presented here.Theoretical investigations by using high frequency solution indicate that the signal in the transversal (azimuth angleθ=90°) is of SH-nature.The radiation of seismic energy is concentrated in vertical direction,but in horizontal direction is zero. The exact solutions of the wave Held and the variation of maximum amplitude of ground displacement with take-off angle,which are calculated by the Cagniard-deHoop technique, agree with results of the asymptotic solution.更多还原