GPS观测得到的天津地区的现今变形

1995年为了监测天津市的地面变形，配合地面沉降的精密水准测量，在天津市布设了一个GPS监测网。从1995年开始，每年的10月或11月进行一次精密GPS测量，到2001年已连续观测7年，在重新系统处理这7年资料的基础上，对天津地区的现今变形进行了研究，并与同时进行的精密水准复测的垂直变形结果进行了比较。结果表明，在扣除了天津地区随同欧亚板块在地球表面的整体运动之后。天津地区仍然有以东向运动为主要特征的水平运动，年速率约为8.4mm/a，这与整个华北地区的东向运动一臻。天津地区的垂直变形主要是因抽用地下水，油，气引起的地面沉降。用GPS测得的沉降量与用精密水准得到的结果相当一致，天津地区的垂直变形主要是因抽用地下水，油，气引起的地面沉降，用GPS测得的沉降量与用精密水准得到的结果相当一致，其偏差均方根值为11.6mm/a。据此对天津地区的地面沉降监测问题提出了建议。

RECENT DEFORMATION DEDUCED FROM GPS OBSERVATION IN TIANJIN AREA

In order to monitoring land subsidence in Tianjin,a GPS network was established in 1995 as a complementary means of the precise leveling. The network has been observed every year in October or November since 1995. Up to 2001 seven times of GPS measurement have been carried out. All the observation data are re-processed recently. On the basis of the processed results the recent deformation in Tianjin area is studied and the vertical deformation results are compared with the ones derived from precise leveling data that are simultaneously observed with the GPS. The results show when the motion of Eurasia plate are removed from the displacements at GPS stations the remain displacements still show the feature of motion to the east at average velocity of 8.4 mm/a.It agrees with the motion of entire North China. The vertical deformation in the Tianjin area is mainly subsidence which is caused by the over withdrawal of underground oil, gas and water. The subsidence quantities deduced from GPS observations are quite coincident with the ones directly obtained from precise leveling. The mean square root error of differences between the values by two kinds of methods is 11.6 mm/a. Finally some recommendation about the subsidence monitoring in the Tianjin area are proposed.