云南强震活动的多层次动力源分析

Analysis on Multiple-level Dynamical Sources of Strong Seismicity in Yunnan

对云南地区多层次动力过程作了分析研究 ,结果表明 ,若以两大板块之间在边界上的相互作用为最高层次的动力作用 ,云南地区现代构造运动至少包括三个层次的动力作用过程 :(1)印度板块和亚欧板块两大地壳板块在喜马拉雅碰撞带东部弧顶和东翼相互作用产生的边界动力源对云南地区产生的直接影响和间接作用 ;还有菲律宾海板块对亚欧板块的北西西向的推挤 ,通过华南地区对云南东部的间接作用 ,构成了云南地区现代构造运动第一层次动力作用 ;(2 )以康滇菱形断块为主体 ,包括川青断块、滇西南断块带等板内断块的整体向南南东—南东方向的相对移动产生的动力作用 ,是第二层次的动力作用 ;(3)由于板内断块边界断裂运动速率的差异 ,主要是水平滑动速率差异造成的板内断块内部次级断块移动产生的动力作用 ,是第三层次的动力作用。对印度板块和亚欧板块两大地壳板块碰撞挤压带东部弧顶和东翼相互作用产生的边界动力源与云南及邻区构造运动、构造应力场分布格局和强震活动关系作了分析研究 ,认为云南及邻区多层次动力作用过程 ,是强震活动时空分布的主要原因。

Analysis and study on multiple-level dynamical process in Yunnan region are made.The results show that recent tectonic movement in Yunnan region should include at least three dynamical processes as follows if interaction in the boundary between the two large plates is the highest-level dynamical action.1.The fist-level dynamical action of recent tectonic movement in Yunna region is constituted by direct and indirect action of the boundary dynamical source on Yunnan region generated by interaction between the Indian and Eurasian plates in east arc top and east flank of Himalayan collision zone and the indirect action on east Yunnan generated by pushing Eurasian plate in NWW through south China of Philippine Sea plate.2.The second-level dynamical action is formed by relatively moving in SSE-SE of intraplate fault blocks composed mainly of Xikang-Yunnan rhombus fault block and including Sichuang-Qinhai fault block and southwest Yunnan fault block.3.The third-level dynamical action is formed by movement of secondary fault blocks in intraplates because of difference of movement rates of faults in the boundary of intraplate blocks,mainly differing on horizontal slip rate.The relation between the boundary dynamical source and tectonic movement,distribution pattern of tectonic stress field and strong seismicity in Yunnan and its neighbouring area is analyzed.Time-space distribution of strong seismicity in Yunnan is caused mainly by multiple-level dynamical action process.