基于GPS的云南地区活动地块现今运动及应变特征分析

The analysis of current crustal deformation and strain characteristics of active blocks in Yunnan region based on GPS

利用GAMIT/GLOBK软件,对云南境内以及川滇交界区域2009年、2011年、2013年3期陆态网络区域网联测数据进行处理,得到欧亚框架下的测站运动速度场。将云南地区划分为4个活动地块及7个次级构造单元,以GPS速度场为约束,建立块体的整体旋转与均匀应变模型(REHSM),采用最小二乘法,得到华南、滇东、滇中、川滇菱块南段、印支、保山及腾冲地块的运动速度。对活动块体运动进行分析,认为云南地块运动方向由SSE向逐渐至SSW向变化,具有顺时针旋转特征,运动幅度由西向东、由北向南逐渐减弱,菱形块体外各块体运动速度大幅衰减。从应变率参数结果看,华南地块、滇东块体主要受SE向压应力场控制,到滇中地块转为SE—SSE向,滇西北地区应力场方向为SSE向,滇西南印支地块为NNW向,滇西南腾冲—保山地块主要受NE—NNE向应力场控制。

GPS data from CMONOC between 2009 and 2013 in Yunnan region were processed by GAMIT/GLOBK, and a velocity field relative to the Eurasian reference frame was obtained. Based on geological division of blocks, the Yunnan region can divided into seven active secondary crustal blocks. Using REHSM model, the present-day Euler rotation vectors of seven secondary blocks are calculated and analyzed based on GPS stations velocities. The velocities of crustal block includes South China block, northwestern Yunnan block, central Yunnan block, South Sichuan-Yunnan rhombic block, Indochina block, Baoshan and Tengchong blocks wera estimated by least-square fitting under the rigid body model. The results indicate that the direction of crustal movement to the area changes from SSE to SSW gradually. The Sichuan-Yunnan rhombic block is characterized by clockwise rotation. The velocities of those blocks outside the rhombic block decrease swiftly. The orientations of principal compressive stress are： SE in eastern Yunnan and South China block, SE-SSE in central Yunnan block, SSE in northwestern Yunnan block, NNW in indochina block,NE-NNE in Tengchong-Baoshan blobk.