【摘要】 利用单台小震初动符号求解宁夏及其邻近地区半年时间窗的小震综合断层面解，发现主压应力方向在中强震前表现出异常形态：（1）主压应力方向离开平均值顺时针（向东）偏转的角度增大；（2）单台记录的P波初动符号在中强震前趋于一致，（3）主压应力P轴的仰角在中强震前有所增大。更多还原

【Abstract】 While using small earthquake first motion signs of single station to solve the syntheticfaultplane solution within half a year in Ningxia and neighboring areas,it is found that the di-rection of principal compressive stress field shows three kinds of abnormal manners: (1 )An-gle increase of principal compressive field direction apart from average value turning coock-wise(towards east); (2)The first motion signs of head waves (P, Pn)recorded by single sta-tion approach the identity ; (3)Some increase in the angle of elevation of principal compressivestress P axis before moderate-strong earthquakes.更多还原