【摘要】 利用１９８９、１９９１年大同－阳高两次地震前后几年的地震记录资料，详细分析了其震源应力场的变化，结果表明，６．１级地震前震源应力场中两个主应力轴的方向曾发生逆转，主压应力袖逆转时间约１０个月，主张应力轴逆转时间为２个月。６．１级主震前４个月，两个主应力轴的方向、仰角都恢复到正常状态，且与华北区域应力场的特征某本一致，而１９９１年５．８级地震前却没有出现上述现象。说明大同－阳高２次地震是在同一震源应力场作用之下孕育、发展的，亦说明５．８级地震是６．１级地震的晚期强余震。指出山西地震带６级以上地震的孕育发生似是在华北区域应力场的作用之下完成的。更多还原

【Abstract】 The paper made use of the earthquake records before and afper 2 Datong-Yanggao earthquakes and ana-lyzed the change of its focal stress field,the result showed that two prhcipal stress axis orientations of the fo-cal stress field before M6.1 earthquake had reversed,the reversed time of the principal compressive stress ax-is was for 10 months,and the extensional stress for 2 months. Two principal stress axis orientations and itsellvations had recovered before 4 months of the M6. 1 main shock.and were consistent with the feature of theNorth China regional stress field ,but no above mentioned phenomena had occurred before M5. 8 earthquake.thus showed that two Datong-Yanggao earthquakes had prepared and developed under the action of same fo-cal stress field,M5. 8 earthquake was the late strong aftershock of M6.1 earthquake.The paper suggests thatM≥6. 0 earthquakes of Shanxi seismic zone prepare and occur under the action of the North China regionalstress field.更多还原