红河断裂的GPS监测与现代构造应力场

GPS MEASUREMENT AND PRESENT TECTONIC STRESS FIELD IN THE HONGHE FAULT, SOUTHWEST CHINA

中德合作于１９８８年和１９９１年两次用ＧＰＳ监测滇西地震预报实验场场区现代构造运动及红河断裂的地壳形变，两期观测的数据处理结果表明，滇西ＧＰＳ观测基线相对定位精度接近１０－７。利用两期观测资料得到的基线变化，并结合构造应力场应变模型，估算得到场区近期构造应力场的应力特性参数，结果表明：该地区应力状态以挤压为主，兼有拉张及右旋剪切，其主压应力方位为Ｎ１７°±１２°Ｅ；由于印度板块在场区西侧的侧向挤压作用，场区内北东向压应力占优势。

GPS measurement were conducted jointly by Institute of Seismology, SSB. China and Institute of Geodesy, University of Hannover, Germany in the Western Yunnan Earthquake Prediction Study Area, over which the Honghe fault is distributed,in 1988 and 1991 respectively. The baseline solutions produced by two-epoch GPS campaigns demonstrate that the relative precision of baseline positioning at a level of better than 1×10 -6 has been achieved as a whole, some approaching 1×10 -7 .The GPS-derived baseline length changes in 1988～1991 are applied to analyze the present tectonic stress field in the area. The direction N17°±12°E of main compression stress estimated by GPS measurement indicates that the stress field is undergone predominantly NNE compression with a right lateral shear faulting, which suggests an increase of tectonic activity in the area caused by forward and shear force of the Indian plate while moving northly.