沿走滑活动断层的基岩河道系统位错--以青藏高原东部为例

SYSTEMATIC OFFSET OF BEDROCK CHANNELS ALONG ACTIVE STRIKE-SLIP FAULTS ON THE EASTERN TIBETAN PLATEAU

河流位错是沿走滑活动断层的重要构造地貌之一。然而,由于河流复杂的自然形态、沿走滑断层容易发生河流袭夺等因素,使得利用河流形态来判断走滑断层的滑动方向、位错量等存在一定的困难。文中系统介绍了利用基岩河道系统位错对沿走滑断层的河流位错地貌进行分析的方法。系统水系位错是构造过程和地表过程沿走滑活动断层相互作用的结果,是穿过走滑活动断层的河流累积位错量的同时在溯源侵蚀作用下向上游方向增长的现象。对青藏高原东部甘孜-玉树、鲜水河、昆仑东段3条走滑断裂带的河流位错地貌进行的解译、测量和统计表明,沿3条断裂带都发育系统水系位错,河流从源头到断层的上游长度(L)越长,其累积的位错量(D)越大,两者之间存在线性相关关系D=a·L。为研究青藏高原东部构造地貌演化过程中走滑断裂带的作用提供了重要依据。

Offset river is one of the characteristic landforms along active strike-slip fault. Whereas because of various factors such as natural meander,river capture,etc,difficulties exist while interpreting slip motion and offset amount using landforms of offset rivers. In this study,we introduced the systematic offset of bedrock channels as a method to analyze offset rivers along strike-slip fault. Systematic offset of bedrock channels is the result of coupling between tectonic process and surface process. It also describes the phenomenon of synchronous accumulation both of the offset amount and the upstream length because of head-ward erosion. Based on the interpretation,measuring and statistics of the offset river landforms,it is found that systematic offset of bedrock channels have developed along the GanziYushu,Xianshuihe and eastern Kunlun fault zones on the eastern Tibetan plateau. There is a linear relationship between the upstream length( L),measured from the headwater to the fault,and the offset amount( D) : D = a·L. This study provides useful implications to the role of strike-slip faults during the geomorphic evolution of the eastern Tibetan plateau.