类乌齐-玉树-玛多剖面重力异常研究

STUDY ON GRAVITY ANOMALY OF PROFILE RIWOQE-YUSHU-MADUO

青海玉树Ms7.1地震发生在巴彦喀拉块体的甘孜-玉树断裂带上。对跨断裂带的重力剖面测线进行了相对重力联测,对观测结果作了大气改正、极移改正、漂移改正,经平差计算后,获取了该剖面的自由空气异常;结合该区1″×1″的ASTER GDEM(2009)地形数字模型,对自由空气异常作了曲率改正、平板改正及高精度的地形改正,得到该探测剖面的完全布格重力异常。分析结果表明:从布格异常的陡变区可初步推断出与地质研究结果一致的断裂构造的位置;在玉树附近沿剖面往东北向出现地壳基底抬升现象,并在清水河附近幅度达到最大,初步推断为印度地壳的俯冲下插对青藏高原东缘的抬升作用的结果。

Yushu Ms7.1 earthquake occurred in the Bayan Har block,exactly the Ganzi-Yushu fault zone.We set up a relative gravity survey lines cross the fault zone and conducted the gravity survey.We processed the raw data,such as atmospheric correction,polar motion correction,drift correction,adjustment calculation,and then obtained the free air anomaly of the profile.After the curvature correction,flat-panel and high-precision terrain correction by using the ASTER GDEM（2009） Digital terrain model（1 ″× 1″）,we obtained a complete profile of the probe Bouguer gravity anomaly.The results show that the location of faults which consistents with the geological results as their is a sudden change zone in the Bouguer anomaly curve;the basement begins to uplift from the place near Yushu to its northeast along the profile,and the maximum rate is at Qingshuihe town.We have concluded that it is resulted from the Indian crust subducting and inserting,making the eastern edge of Qinghai-Tibet Plateau uplifting.