GPS技术应用于中国地壳运动研究的方法及初步结果

文中主要就中国利用GPS等空间测地资料研究地壳运动、构造变形 ,以及用于地震预测探索方面 ,从方法技术和近年来取得的一些初步结果进行了概要性论述。介绍了利用GPS技术资料研究地壳水平运动速度场、水平应变场、建立地壳运动模型等方法研究的进展。由GPS观测给出的地壳水平运动初步结果表明 :中国大陆现时水平运动在全球参考系中为整体向东 ,并兼有顺时针扭转运动。西部地区构造形变强烈 ,整个青藏块体及其边界带 ,以及新疆西部是应变值最高的区域 ,水平应变场主压应变优势分布方向为近NE向 ,空间差异显著 ,反映了印度板块碰撞推挤和青藏块体强烈构造运动的影响。中国大陆东部水平运动的差异性不显著。强震分布于地壳运动的大小、方向显著变化的区域 ,大地震通常发生在水平剪应变高值区或其边缘 ,尤其是与区域主干断裂的构造活动背景相一致的剪应变率高值区。

APPROACHES AND PRELIMINARY RESULTS OF CRUST MOVEMENT RESEARCHES BASED ON THE GPS IN CHINA

Monitoring crust movement by means of GPS techniques started from the end of 1980s in China. Through supporting scientific projects, the scale of GPS monitoring network of China mainland is gradually spread and added. National important project “Crustal Movement Observation Network in China (CMONOC)” was primarily established in 1997, and has come to be able for monitoring integrated crust movement in China mainland and for high resolution monitoring the movement in some seismic actives area in the northern China, Sichuan—Yunnan, and northeastern part of Qinghai—Tibet block. With the completion of the national important foundation research project “Mechanism and prediction of strong earthquake” based on the new geodetic techniques, the applications of GPS technique to Earth science have made great achievements.This paper summarizes approaches and preliminary results in researches of crust movement, tectonic deformation and earthquake prediction based on the GPS observations. The research approaches for crust horizontal velocity field, horizontal strain field and modeling the crust movement are introduced. The preliminary results from GPS horizontal movements show that the recent horizontal movement in China mainland is toward to east, and with clockwise torsion movement. In western China mainland tectonic deformation is strong. Whole Qinghai—Tibet block and its margins and the western part of Xinjiang are the areas with highest strain, and the potential direction of principal compressional strain toward north|east, and the regional difference is clear, which demonstrated the collision and jostle effects of Indian plate, and strong tectonic movements of Qinghai—Tibet block. However, the difference in horizontal movements in eastern China mainland is not distinct. Strong earthquakes are usually distributed in the region with high movement velocity and great direction change, and in the area with high shear strain or in its edges, especially, in the high shear strain area consistent with the direction of main fault.