用初动振幅比求震源机制的球面拟合法

本文根据非均匀破裂圆盘位错模式在均匀介质中给出的远场位移解,通过直角坐标系的正交变换,导出了一组震源节面方程。其中,P波理论地震图的计算,考虑了介质的非弹性吸收和仪器暂态特性的影响。节面方程采用球面量板求解:取4个台的（?）折算振幅比,直接拟合其辐射图型因子,即可在球面上求得震源两个节面。最后,用本文方法分析了新丰江水库区一个中等强度的震例,所得断层面解与按（?）初动符号分布确定的结果甚为接近。

SPHERE-FIT METHOD FOR DETERMINING FOCALMECHANISM FROM AMPLITUDE RATIOSOF INITIAL -WAVES

Starting with solution of the far-field displacement for a model of circular shear crack with non-uniform dislocation in homogeneous medium, a system of equations of source nodal planes in which the amplitudes of P-waves are computed under consideration of the anisoelastic absoption of the medium and transient response of seismograph is deduced from orthogonal transformations of rectangular Cartesian coordinates. A couple of the nodal planes which is equivalent to the solution of the equations can be searched out through a spherical nomograph provided that the ratios of P introduced amplitudes at each of four seismic stations are fitted to the radiation pattern for the P-wave on this sphere. An example of the moderate shock in the Xinfengjiong region shows that the fault-plane solution in this paper appears to be identical with that determined by the polarities of P-wave first motions.