台海地区的地壳运动与变形

CRUSTAL MOVEMENT AND DEFORMATION IN TAIWAN AND ITS COASTAL AREA

利用福建沿海GPS网和台湾-吕宋GPS网站速度数据和两个网数据处理中共用的IGS永久站数据,实现了两个GPS网参考框架和速度场的统一.分析台海地区的速度场发现,福建沿海、台湾海峡与台湾岛北部地壳的水平运动完全一致,运动方向约为东偏南26.0°,运动速率约为39mm/a;台湾岛东部的海岸山脉地区发生了相反变化,运动方向为北偏西30.0°,运动速率约为33.3mm/a;在台湾岛的南端存在南偏西50.0°方向的运动,运动速率约为13mm/a.若以福建沿海的几何中心为参考基准,台湾岛存在一致的（岛的北端除外）北西向运动,方向北偏西约50.0°,东海岸的速率最大为61mm/a,向西逐渐减小.应变场分析表明,台海地区存在统一的应变场,主压应变方向为北西48.0°,主张应变方向为北东42.0°.主压应变速率,台湾岛的东海岸为3.436X10-7/a,向西逐渐减小,到福建沿海减小到1.861X10-8/a.菲律宾海板块在台湾岛东部与欧亚板块的碰撞俯冲是台海地区地壳运动、变形和发生大地震的主要驱动力.本区的主压应力方向约为北西55.0°.

Based on the station velocity data obtained from Fujian coastal GPS network and Taiwan-Luzon GPS network and the data obtained from IGS permanent stations commonly used in the data processing of both networks, the uniformity of reference frames and velocity fields of both GPS networks is realized. It has been discovered from the analysis on the velocity field in Taiwan and its coastal areas that the horizontal crustal movements in the coastal area of Fujian, Taiwan Strait and the northern part of Taiwan Island are fully consistent. The movement direction is around 26. 0°E by S and the rate is about 39 mm/a. The opposite variation occurrs in the coastal mountain area in the eastern part of Taiwan Island with the movement direction of 30. 0°N by W and the movement rate of about 33. 3 mm/a. In the southern end of Taiwan Island, the movement direction is 50.0°S by W and the movement rate is about 13 mm/a. If the geometric center of Fujian coast is used as the reference datum, Taiwan Island has a consistent (except its north end) NW-trending movement with the direction of around 50. 0°N by W. The maximum rate of 61 mm/a occurs along the eastern coast and decreases gradually towards west. Theanalysis of strain fieldindicates that Taiwan and its coastal area have a uniform strain field with the principal compressive strain direction of N48. 0°W and the principal tensile strain direction of N42. 0°E. The principal compressive strain rate along the eastern coast of Taiwan Island is 3. 436X10-7/a, which decreases gradually towards west and reaches 1. 861 X 10-8/a to Fujian coast. The collision and underthrust of Philippine Sea plate with Eurasian plate in the eastern part of Taiwan Island can be considered as the principal force for the crustal movement, deformation and great earthquake occurred in Taiwan and its coastal area. The direction of principal compressive stress in the area is about N55.0()W.