SEISMOLOGY AND GEOLOGY ›› 2013, Vol. 35 ›› Issue (4): 793-804.DOI: 10.3969/j.issn.0253-4967.2013.04.009

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YAN Ji-ming1,2,3, WEI Zhan-yu1,3, HE Hong-lin1,3   

  1. 1 Key Laboratory of Active Tectonics and Volcanoes, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
    2 Earthquake Administration of Shanxi Province, Taiyuan 030021, China;
    3 National Taiyuan Observatory of Continental Rift Dynamics, Taiyuan 030021, China
  • Received:2013-09-25 Revised:2013-09-25 Online:2013-12-30 Published:2014-01-03


闫计明1,2,3, 魏占玉1,3, 何宏林1,3   

  1. 1 中国地震局地质研究所, 活动构造与火山重点实验室, 北京 100029;
    2 山西省地震局, 太原 030021;
    3 太原大陆裂谷动力学国家野外科学观测研究站, 太原 030021
  • 通讯作者: 何宏林,研究员,
  • 基金资助:

Abstract: The degradation of fault scarps in unconsolidated deposits can be accurately simulated. Under the appropriate correction,high-accuracy digital models can be built for the fault scarps evolution. These models provide the basis for estimating the age of faulting. In this paper we measured a series of artificial fault scarps with different slope angles in frequency of once a month,and found that the artificial fault scarps with slope angle above 30° are in an unstable stage and a group of parameters are acquired. There are obvious differences in erosion thicknesses,daily erosion rates and annual recession rates of artificial fault scarps. Besides the greatest erosion thickness of 6.13mm on the slope of 80°,there is a peak value of 5.24mm at the scarp of 50°,and the erosion thicknesses then gradually reduce for other slopes. There are the similar distribution characters in the daily erosion rates and the annual recession rate. Besides the recession rate of (6.74±0.26)mm/a on the slope of 80°,the greatest value of (7.41±0.84)mm/a is observed at the scarp with slope angle of 50°.But there is an abnormally high value of (8.19±1.16)mm/a in recession rate for scarps with a slope of 30°,which may result from the low angle. As the angle reduces,the deviation of the erosion thickness from the recession distance becomes bigger. The average recession rate of 5.8mm/a can be used as the correction value of the evolution of the normal fault scarps in Shanxi rift system,though it is based on the measurement of one year and has larger limitations. In addition,there is an obvious difference between field observations and ideal model. The accumulation amounts at the foot of scarps are not equal to the erosion amounts of scarp surface,due to that part of weathering material was washed away by the rainwater. The experimental observations show that there are not obvious accumulations during the rainy season(until October)due to rushing of rainwater,but the loess accumulations appear at the foot of scarp after the snow melts in winter. According to the measurements of one year,41.6% of total erosion amount is washed away by rainwater at the scarp with slope angle of 80°,and for others scarps the results are 52.4%,47.6%,50.6%,60.5% at slope angles of 70°,60°,40°,respectively.

Key words: erosion rate and retreat rate, loess, man-made slope, fault scarp

摘要: 松散沉积物中断层崖形态的演化可被准确的模拟,经适当的校正,可提供断层崖演化的高精度数字模型,这些模型是确定断层崖出露年龄的基础。通过一系列不同坡角的人工坡面的1年高精度观测,发现30°以上的人工坡面都处于不稳定阶段,并获得了一系列后退参数。不同角度坡面的侵蚀厚度、日侵蚀速率和后退速率都存在差异。除了80°坡面6.13mm的最大侵蚀厚度外,侵蚀厚度在50°坡面处存在一个峰值5.24mm,并存在逐渐向高角度和低角度降低的趋势。日侵蚀速率和年后退速率也存在类似的分布特征,除了80°坡面为(6.74±0.26)mm/a外,后退速率在50°坡面最大形成峰值(7.41±0.84)mm/a,而在30°坡面处出现一个明显的异常高值(8.19±1.16)mm/a,可能与低坡角有关,因为随着坡角减小侵蚀厚度与后退量的偏离越来越大。尽管只有1年的观测结果,而且是不同坡角陡坎的平均值,存在较大局限性,但平均后退速率为5.8mm/a,仍可作为山西地堑系黄土层内正断层坎的校准值。此外,实际观测与理想模式存在较大差异,断层崖前的坡脚碎屑物堆积并不等于断层崖的全部侵蚀量,部分侵蚀风化碎屑物会被雨水冲刷掉。实验观测显示,雨季(至10月份)各坡面表面均被雨水冲刷侵蚀,但坡脚却没有明显的黄土堆积;冬季积雪融化后,坡脚处出现明显的黄土碎屑堆积。对比全年的观测结果得到:80°坡面上1年内黄土侵蚀量的41.6%被雨水冲走,其他坡面分别为52.4%(50°坡面)、47.6%(70°坡面)、50.6%(60°坡面)、60.5%(40°坡面)。

关键词: 侵蚀率和后退速率, 黄土, 人工坡面, 断层崖

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