川滇地块的震源力学机制、运动速率和活动方式  

FOCAL MECHANISMS, DISPLACEMENT RATE AND MODE OF MOTION OF THE SICHUAN-YUNNAN BLOCK

作　　者：程万正[1] 刁桂苓[2] 吕弋培[1] 张永久[1] 李桂芳[1] 陈天长[1] 

机构地区：[1]四川省地震局,成都610041 [2]河北省地震局,石家庄050021

出　　处：《地震地质》2003年第1期71-87,共17页Seismology and Geology

基　　金：国家重点基础研究发展规划项目 (G95 130 5 0 5 )资助。

摘　　要：用 4 4 2次中强地震的震源机制解分析了川滇次级地块应力场的优势方向。使用 771次 3级左右地震的滑动角λ参数统计确定震源断层的错动方式 ,并用中强地震P波初动解的N轴仰角的统计分布结果得到的震源断层错动或滑动型式去佐证。拟合中强地震的矩张量速率式 ,计算了川滇次级地块各地震构造区的年均滑动速率 ,并进行比较。根据 1980— 2 0 0 1年川青地块、雅江地块和滇中地块边界断裂带跨断层短水准、短基线定期复测结果 ,分析了水平和垂向年均形变速率。川滇地块间的运动是不均匀的。川青地块的运动方向为SEE。雅江地块压应力场优势方向为SSE ,相对川青地块的运动速率更大。滇中地块承袭雅江地块的运动方向 ,略偏东。密支那滇西地块压应力场有 2组优势方向 ,存在向NE方向的推挤和SSE方向的逃逸 ,活动速率大。In this paper, Sichuan-Yunnan and its adjacent areas are divided into Yajiang, Central Yunnan, Sichuan-Qinghai, Central Sichuan, and Myitkyina-West Yunnan blocks. The mode and rates of motion of these blocks and their boundaries are studied separately. The predominant direction of the principal compressive stress axes within the blocks is analyzed in term of focal mechanism solutions of 442 moderate strong earthquakes. The models of focal faulting are determined through the rake angles λ obtained from source parameters of 771 events with magnitudes about 3 or more, and they are evidenced by focal faulting or slip modes derived from the distributions of N axis plunges of P-wave first motion solutions for moderate-strong earthquakes. A comparison is made between the moment tensor rates for moderate-strong earthquake and the calculated annual average slip rates of each seismotectonic zones within the blocks. Based on regular resurveying of across fault short level lines and baselines during the period of 1980-2001 along the border of the Sichuan-Qinghai, Yajiang and Central Yunnan blocks, the annual average rates of horizontal and vertical deformation for each site are analyzed. The motion rates of the Sichuan-Yunnan Block are inhomogeneous. The Sichuan-Qinghai Block moves toward SEE direction, and the predominant direction of the principal compressive stress axis falls in the range of N100°～130°E. The motion rate of this block is smaller than that of the Yajiang block, implying a delayed motion relative to that of the later. As a result, the Xianshuihe Fault between these two blocks displays a strong left lateral displacement. In addition to earthquakes of strike-slip type, the earthquakes of reverse dip-slip type are also predominant in the Sichuan-Qinghai Block. The predominant direction of the principal compressive stress axes in the Yajiang Block is within the range of N160°～170°E, i.e. SSE. The motion rate of this block is larger than that of the Sichuan-Qinghai Block, and the percentage of st

关 键 词：川滇地块 震源机制 地块运动 运动速率 

分 类 号：P315.33[天文地球—地震学]