滇西重力场动态趋势变化与断层运动

摘要

Controlled by absolute gravity data, mobile gravity data of western Yunnan network from 1985 to 2010 are processed with adjustment of average accuracy of 12×10-8 ms-2 . The characteristics of single point gravity variation curve are with seasonal fluctuation and trend movement (up or down) in long-term. The gravity dynamic variation of some points is consistent with preparation process of Lijiang Msl. 0 earthquake. The annual change rate of gravity from long-term observation can reflect the trend variation of gravity field in a time period. The annual change rates of gravity in 1985 - 1995 and 1996 -2003 might reflect the energy accumulation and release before and after the Lijiang Ms7. 0 earthquake. Since 2003, the rising velocities of gravity are over 10 × 10-8ms-2/a a-long the Jianchuan fault, Heqing-Eryuan fault and the northern segment of Red River Fault Zone. On the basis of the initial fault movement model, the forward simulant annual changing rates of gravity are similar with the measured values. It indicates that fault movement has great contribution to the gravity field change. The annual fault movements inversed by annual change rate of gravity are consistent with the geological results, and basically reflect its active characteristics.%以绝对重力做控制,对滇两网1985-2010年流动重力资料进行统一平差处理,平均点值精度为12×10-8ms-2/a;单点重力时变曲线主要呈现出季节性的上下波动和长期性的上升或下降趋势运动,部分点重力动态变化与丽江7.0级地震孕育过程相吻合；基于长期观测的重力场年变化率反映了重力场在一段时期内的趋势性变化:1985-1995年和1996-2003年年变化率图像可能反映丽江7.0级地震前后能量的累积、释放和调整,2003年以后剑川断裂、鹤庆-洱源断裂和红河断裂北段附近重力值上升速度均超过10×10-8ms-2/a；基于初始断裂运动模型正演模拟的滇西重力场年变化率图像与实测图像非常相似,说明断裂运动对重力场趋势性变化有重要贡献；基于长期观测的重力场年变化率反演的滇西主要活动断裂年错动量与地质上给出的结果相仿,基本上反映了各断裂的活动性质.