Abstract: The Huoshan piedmont fault is a small watershed region in Shanxi Province. We utilized the high-resolution DEM data and the stream-power incision model which describes the relationship between the tectonic uplift and fluvial incision to analyze the S-A double-log graph, concavity index (θ)and steepness index (logk_s) of the 64 channels across this fault and discuss their responses to the tectonic movement of the fault. The results show that (1)the S-A double-log graphs all exhibit an obvious convex form, which is the direct expression of the response to the situation that the bedrock uplift rate is higher than the fluvial incision rate. (2)All of the concavity index (θ)values of 64 channels are lower than 0.35 with an average value of 0.223, much lower than the empirical value (0.49)of the rivers in steady state. These low values are the quantitative reflections of the channels' slightly concave profiles. Meanwhile they imply that these channels across the fault are very young. There is no enough time for them to adjust the profiles through the fluvial incision to the steady state because of the fault's frequent and strong tectonic movements. (3)The steepness index values of the channels located in the Laoyeding Mt. are highest, while they are lower in the northern and southern mountains. Moreover, the steepness index values of the channels in the northern mountains, on average, are higher than those of the channels in the southern mountains. To a certain extent, this distribution of the steepness index corresponds to the difference in the uplift rates of the Huoshan piedmont fault. It means that the uplift rate of the middle fault segment in the Laoyeding Mt. is highest, and the uplift rate of the northern segment is higher than that of the southern segment.

Key words: Huoshan piedmont fault, stream-power incision model, channels, DEM, S-A double-log graph, concavity index, steepness index, response to tectonic movement

摘要： 利用能够反映构造隆升作用与河流下切侵蚀作用之间关系的河流水力侵蚀模型，以小流域性的霍山山前断裂为实验区，基于高分辨率DEM数据，分析了64条横跨断裂发育的冲沟的S-A双对数图、凹曲指数（θ）与陡峭指数（logk_s）；研究了它们对霍山山前断裂构造活动的响应特征：1）冲沟的S-A双对数图基本都呈现出明显的上凸特征，这是对断裂区域构造隆升速率大于河流下切侵蚀速率的直观响应；2）冲沟的凹曲指数θ值均<0.35，平均值仅为0.223，远低于均衡河道的经验平均值（0.49），这是冲沟纵剖面下凹程度低的直接的量化表达，反映了冲沟的发育是很年轻的，而其原因主要是霍山山前断裂频繁而强烈的构造运动使冲沟没有足够的时间通过下切侵蚀作用来调整剖面形态；3）冲沟的陡峭指数logk_s值呈现出老爷顶一带最高，南北两侧较低，而且北部比南部高的分布特征；这在一定程度上指示了霍山山前断裂在老爷顶一带隆升速率最大，南北两侧较低，而且北部隆升速率比南部高。

关键词: 霍山山前断裂, 河流水力侵蚀模型, 冲沟, DEM, S-A双对数图, 凹曲指数, 陡峭指数, 构造响应