断层水平错动下河流演变过程的数值模拟研究

摘要/Abstract

摘要： 在活动构造区, 河流地貌对构造活动具有明显的响应, 地貌形态和水系形态能够很好地记录构造活动信息。基于地貌演化理论, 考虑断层的左旋错动作用及降雨等因素, 利用数值模拟方法, 定量研究河流形态在断层水平错动及流水侵蚀内外力作用下的动力学演变过程。初步的计算结果显示了河流形态与断层走滑运动的耦合效应。断层发生水平左旋滑动促使该处河道两侧的陡坎发生相对错动, 形成弯转水系, 伴随河流的侧向侵蚀作用, 河道上下游连续被拓宽, 河道下游右侧堆积了较厚的沉积物, 而河道上游左侧由于受到较强流水侵蚀作用很难堆积沉积物。分别对河道上游和河道下游的横剖面形态进行对比分析, 表明由于断层水平错动效应, 使得河道下游两侧呈现不对称特征, 而河道上游依然保持着明显对称性。同时, 河道剖面形态对断层水平错动作用有积极的响应, 由于断层持续左旋走滑运动, 断层处剖面的高程突然增加, 坡度也随之突然变陡。数值模拟结果与实际地质考察结果有着很好的一致性, 证明了理论和数值模型的可靠性。

关键词: 河流演变, 地貌演化, 走滑断层, 数值模拟

Abstract: Fluvial landform and stream pattern have obvious responses to active tectonics, we should be able to use the landscape as an archive of the active tectonics. In order to better understand the river evolution with left-lateral strike-slip faulting, we use numerical simulation based on the geomorphic evolution theory to model channel evolution. The tectonic lateral-displaced rate and rainfall factors are the main elements controlling the landform development. Initial numerical results demonstrate quantitatively dynamic evolution processes of a channel under interactions between lateral-displaced faulting and water erosion. Numerical results suggest strong coupling effects between stream patterns and active strike-slip faults. The channel pattern becomes bending, because both sides of the stream generate relative lateral-displacement under influence of strike-slip faulting. The whole stream channel is continuously widenly because of lateral water erosion. A lot of sediment accumulated at the right side of the downstream, however, the left side of upstream is difficult to deposit sediment because of the strong water erosion. The results also demonstrate an clear asymmetry of the two sides of the downstream, but the two sides of the upstream still show obvious symmetry. Profile elevation at the fault increases abruptly, and the slope suddenly become steepening. Based on more reasonable numerical model, numerical simulation can be applied more effectively to quantitative analysis of typical regional geomorphic evolution.

Key words: River evolution, Geomorphic evolution, Strike-slip fault, Numerical simulation

中图分类号:

P315

严珍珍, 张怀, 范湘涛, 杜小平, 石耀霖. 断层水平错动下河流演变过程的数值模拟研究[J]. 地震, 2013, 33(4): 105-114.

YAN Zhen-zhen, ZHANG Huai, FAN Xiang-tao, DU Xiao-ping, SHI Yao-lin. Numerical Simulation of River Evolution Processes under Strike-slip Faulting[J]. EARTHQUAKE, 2013, 33(4): 105-114.

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