地应力测量结果的校验和震前观测事实

A METHOD FOR TESTING CRUSTAL STRESS MEASUREMENTS AND THE OBSERVATIONS BEFORE TWO EARTHQUAKES

广东省琼中和甘肃省永靖两地应力站的观测资料,在经过统计分析处理和力学校验后表明,1982年1月25日广东省崖县4.1级地震和1984年1月6日甘肃省武威5.5级两次地震前,相对稳定的区域应力场在孕震后期可能分别受到扰动。测区附加应力状态变化的共同特征是:(1)最大水平主应力曲线呈现非线性变化;(2)主应力方向发生系统偏转;(3)应力的变化趋势在震后迅速恢复稳定,但附加应力水平有所下降。

The observations from two crustal stress observatories at Qongzhong (Guangdong Province) and Yongjing (Gansu Province) show that the relatively stable regional stress field might have been disturbed during the late preseismic stages before the Yaxian earthquake (M = 4.1) of Jan. 25,1982 in Guangdong Province and the Wuwei earthquake (M = 5.5) of Jan. 6,1984 in Gansu Province. The characteristics of change of the additional stress state in the observation area are: 1. The curves of the major horizontal principal stress show nonlinear changes; 2. A systematic rotation of the principal directions of additional stress takes place; 3. The tendency of change of the stress recovers with considerable speed after the seismic events,but the values of additional stress has decreased. The College of Economic Management,Beijing Union University; Institute of Earth's Crust Dynamics,State Seismological Bureau; Seismological Bureau of Ningxia Huizu Autonomous Region; Seismological Bureau of Guangdong Province; Lanzhou Seismological Institute,State Seismological Bureau.