Abstract: An earthquake of M5.2 occurred in Cangshan,Shandong Province on September 20,1995. Abnormal changes and their time-space evolutionary features of the azimuth and plunge of the principle stress axes and ratio of their contrary symbols before this event are analysed. Possible causes of these changes are briefly discussed which can provide background evidence for studies of other kinds of precursorary anomalies.

Key words: Stress field, Anomaly, Focal region

摘要： 从1995年9月20日山东苍山5.2级地震前源区及其附近不同小区应力场方向的动态变化入手,分析了主应力轴方位、仰角及其矛盾符号比等参量在5.2级地震前的异常变化及其时空演变特点,简析了可能成因,可为研究震前其它各类前兆异常提供背景依据。

关键词: 应力场, 异常, 震源区