菏泽5．9级地震前震源附近及外围区应力场的某些变化
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摘要
以格点尝试法求解的小区域平均震源机制解资料，研究了１９８３年菏泽５．９级地震前、后震源附近及其外围不同区域应力场的变化，发现震前震中附近约３°×３°范围内小震应力场有异常变化，开始出现时间为震前５－６年。主要表现为主压应力轴Ｐ轴向大区域应力场方向“集中”继而“转向”、恢复－发震的变化过程，主张应力轴Ｔ轴仰角和矛盾符号比也出现时间上大体同步的变化，且震源附近与外围区变化特点不同。反映了震源附近复杂的物理过程及源区与场区应力场的动态变化差异。
By using the data of mean focal mechanism solusions in small area obtained by grid point test method, the variations of stress field in the epicenter and adjacent areas before and after the Heze earthquake of Ms 5.9 are studied in this paper and it is found that anomalouls variations in stress field occurred within about 3°×3°around the epicenter five to six years before the earthquake; in the initial stage, the direction of main compression stress axis (P axis) was concentrated on that of stress field in large region, later, turned and then returned untill the earthquake occurrence.Almost simultaneons variations in elevation angles of main tensile stress axis (T axis) and contradictory sign rations also were found in same period,and the variation features of these parameters in the epicenter were not analogous to that in its adjacent area, which indicates complex physical process in the epicenter and its adjacent areas before the earthquake and difference of dynamic variation in stress field between the focal and field regions.
By using the data of mean focal mechanism solusions in small area obtained by grid point test method, the variations of stress field in the epicenter and adjacent areas before and after the Heze earthquake of Ms 5.9 are studied in this paper and it is found that anomalouls variations in stress field occurred within about 3°×3°around the epicenter five to six years before the earthquake; in the initial stage, the direction of main compression stress axis (P axis) was concentrated on that of stress field in large region, later, turned and then returned untill the earthquake occurrence.Almost simultaneons variations in elevation angles of main tensile stress axis (T axis) and contradictory sign rations also were found in same period,and the variation features of these parameters in the epicenter were not analogous to that in its adjacent area, which indicates complex physical process in the epicenter and its adjacent areas before the earthquake and difference of dynamic variation in stress field between the focal and field regions.
引文
［1］山东省地震预报研究中心，地震远源前兆的初步分析，地震监测与预报方法清理成果汇编／综合预报分册，地震出版社，1989．［2］周翠英等，山东地区近期应力背景分析，地震，4期，1992．［3］周翠英等，1983年菏泽5．9级地震前后鲁西豫北地区小震应力场的变化，地震，4期，1987．［4］全国地震综合分析预报清理攻关组，地震综合预报探索二十年──全国地震综合预报清理研究总结，地震监测与预报方法清理成果汇编／综合预报分册，地震出版社，1989．［5］贾占岭，菏泽5．9级地震前后的地壳垂直形变特征，地壳形变与地震，4，1984．［6］赵金瑞，菏泽5．9级地震的垂直形变特征，地震学刊，2，1985．［7］赵兴兰等，聊城－兰考断裂带地震活动图象，华北地震科学，2．2．1984．［8］许忠淮等，由多个小地震推断的华北地区构造应力场的方向，地震学报，5，1983．
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