丽江7.0级和唐山7.8级地震前形变场动态演化与异常特征

对１９９６年丽江７．０级和１９７６年唐山７．８级地震前的形变场动态演化过程做了对比分析，结果表明：①两次强震前形变场均存在大范围垂直差异运动增强以及与构造相关的形变高梯度带（区）；②震前数年（或更长）垂直形变场的趋势改变，并出现形变局部化。结合强震前区域地震活动，研究了这两次地震前垂直形变场动态演化与孕震形变的异常特征，认为与构造相关的强烈差异运动是孕震应变能积累的主要方式。

DYNAMIC EVOLUTION AND ABNORMAL CHARACTER OF DEFORMATION FIELD BEFORE LIJIANG M s7.0 AND TANGSHAN M s7.8 EARTHQUAKES

The dynamic evolution process of deformation field before Lijiang M s7.0(1996)and Tangshan M s7.8(1976) earthquakes are comparatively analysed.The results indicate that (1)the vertical differential movement of deformation field is macroscopically heightened and the high deformation gradient belt related to the tectonic of which is presented before two earthquakes.(2)the tendency of vertical deformation field is changed and the localization of deformation field is formed in several years (or more)before earthquakes.Then combining the seismicity before earthquakes,the dynamic evolution of vertical deformation field and the abnormal character of seismogenic deformation are further studied. Some conclusions give certain reference for forecasting the macroquake with the geodetic deformation.