台湾两次7级地震前后福建沿海地区地壳运动的变化

CRUSTAL MOVEMENT CHANGE OF COASTAL AREA OF FUJIAN SURVEYED BY GPS BEFORE AND AFTER TWO M7 EARTHQUAKES IN TAIWAN

福建沿海地区GPS网从1995年建设至今已积累了6期观测资料,分析该网各GPS站位移变化与运动速度变化的时间序列,发现在1999年9月20日(UTC)台湾集集Ms7.7大地震与2001年12月18日(UTC)花莲东Ms7.6大地震前,各GPS站同步出现了向西与向北位移的大幅度偏移,即向东与向南运动的速度明显减小。在集集Ms7.7大地震发生后,各GPS站出现了同步的向东与向南位移的大幅度偏移,即向东与向南运动的速度大幅度增加。福建沿海地区在1997～2001年期间出现的地壳运动的变化不仅在时间上与集集、花莲东两次7级大地震的孕育发生相关,而且二者在形成机理上一致,都是由孕育这两次地震的应力场决定的。

The GPS network of Fujian has been surveyed 6 times from 1995 to now. After analysing the time sequences of the changes of displacement and movement velocity, we have discovered large westward and northward sync-displacement of GPS sites, i.e. eastward and southward movement velocity decrease obviously before Chi-Chi Ms7.7earthquake in Sept. 20, 1999 （UTC） and Ms7.6 in eastern of Hualian in Dec. 18,2001 （UTC） and large eastward and southward sync-displacement of GPS sites, i.e. movement velocity increase much after Chi-Chi Ms 7.7 earthquake. The crustal movement change in 1997 ～ 2001 in coastal areas of Fujian was closely related to preparation and occurrence of Chi-Chi and eastern of Hualian earthquakes not only in time, but also their preparation mechanism are consist with each other since they were caused by strain field growing along with the two earthquakes.