首都圈地区现今地壳运动的GPS观测与构造活动模拟

利用首都圈地区1992~2004年间280多个GPS点位复测资料,获得了该地区高精度的地壳形变速度场,相对欧亚板块的水平速度场由北向南由4 mm/a逐渐增加到9 mm/a;采用边界元(BEM)理论及位移不连续的多边形元素构建断层的三维模型,并利用均匀介质且各向同性的半无限线弹性空间模型反演计算了断层滑移量,模拟了GPS点位的位移场,在此基础上获得了主要活动断层和首都圈地区的地表、地表下15km和25 km剖面的静态位移场、应力及应变场。结果表明,GPS点位的模拟位移场与观测值在南北向和东西向的误差分别为0.68 mm及0.77 mm,各个主要活动断层在1992~2004年间的构造活动较弱,随着深度的增加,剖面的应变逐渐增加。

GPS Measurements and Tectonics Activity Simulation of Present-day Crustal Deformation in China's Capital Region

An accurate crustal deformation field is derived from repeat surveys of 280 GPS stations during 1992-2004 in China's capital region.It shows that the horizontal rate relative to stable Euro-Asia plate ranges from 4 mm/a in the north to 9 mm/a in the south.Boundary element method(BEM) and displacement discontinuity method(DDM) are used to establish a 3D faults construction of the capital region.The faults slip is calculated and the displacement of GPS sites is simulated in a linear-elastic,homogeneous and isotropic half-space.Consequently,the quasi-static displacement,strain and stress fields of main active fault surfaces and profiles in earth's surface,15 km and 25 km underground in capital region are computed.The results indicate that the difference of GPS measurements and simulations is 0.68 mm and 0.77 mm along NS and EW,respectively.The tectonics activities of main faults are weaker during 1992-2004.The profile strain is proportional to the depth underground.