重复绝对重力测量观测的滇西地区和拉萨点的重力变化及其意义  

GRAVITY CHANGE DETECTED BY REPEATED ABSOLUTE GRAVITY MEASUREMENTS IN THE WESTERN YUNNAN AND LHASA,CHINA AND ITS IMPLICATION

作　　者：王勇[1] 张为民[1] 詹金刚[1] 郝兴华[1] 王虎彪[1] 许厚泽[1] 

机构地区：[1]中国科学院测量与地球物理研究所,武汉430077

出　　处：《地球物理学报》2004年第1期95-100,共6页Chinese Journal of Geophysics

基　　金：国家自然科学基金资助项目 (4 0 2 740 2 0 );中国科学院知识创新项目 (KZCX2 10 6;KZCX2 10 9)

摘　　要：根据近年来在滇西地区和西藏拉萨绝对重力点上的一些新的绝对重力重复观测结果 ,对 1990年以来在这些点上绝对重力重复观测结果进行了分析 .滇西地区的 5个绝对重力观测点的近 10年的重复观测结果表明 ,大部分观测时段没有出现与地球动力学事件有关的重力变化 ,只有丽江和洱源 2个绝对重力观测点的观测结果显示丽江地震前后有变化 .为了研究该重力变化的原因 ,本文正演模拟了出现重力变化期间丽江地震同震位错引起的重力变化 ,模拟结果与实际观测结果有较好的一致性 .西藏拉萨近 10年以来的重复观测结果给出了拉萨点的绝对重力值以 - 1.82± 0 .9× 10 - 8m·s- 2 ·a- 1 速率下降 ,这从重力学的角度反映出青藏高原的隆升 .对拉萨点的重力变化机制进行了探讨 ,根据印度板块与欧亚大陆俯冲模型计算的拉萨点重力变化速率与观测到的重力变化速率较一致 ,表明现今拉萨地区重力变化是由于印度板块与欧亚大陆俯冲所引起 .根据印度板块向欧亚大陆俯冲的位错模型计算的拉萨点的重力变化与地表垂直位移的关系 ,将重力变化转换为拉萨点的隆升速率为 8.7mm a .The observed results of repeated absolute gravity measurements since 1990 at the western Yunnan and at the Lhasa stations are analyzed, together with some new observed data at these stations. The repeated observation results during about 10 years at five stations in the western Yunnan indicate that no significant gravity changes related to the geodynamical events were observed in most observation epochs. Significant gravity changes have been detected at Lijiang and Eryuan stations in the western Yunnan before and after Lijiang earthquake ( M S=7.0). We modeled the gravity changes caused by the co seismic dislocation during the Lijiang earthquake, that are in good agreement with the observed data. The gravity changes with time about 10 years at Lhasa station have a slop of -1.82±0.9×10 -8 m·s -2 ·a -1 , indicating that Qinghai Xizang plateau has an uplift. The mechanisms of gravity changes at Lhasa were investigated. We calculated the gravity change rates based on the model of India plate to Eurasia subduction. The computed gravity change rate at Lhasa is ingood agreement with observed one, indicating that present gravity changes at Lhasa were caused by the India plate to Eurasia subduction. The Lhasa has an uplift of 8.7mm/a translated from gravity changes using computed ratio of the gravity changes to the vertical displacements from the dislocation model of the India plate to Eurasia subduction.

关 键 词：绝对重力测量 地球动力学 重力变化 丽江地震 板块碰撞 

分 类 号：P223.1[天文地球—大地测量学与测量工程]