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活动断层对泥石流的影响及其量化评估研究
Alternative TitleThe influence of active fault on debris-flow formation and activity and its quntitative assessment reserch
Language中文
苏鹏程
Thesis Advisor韦方强
2013
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name博士
Degree Discipline自然地理学
Keyword活动断层 泥石流 定量评估 危险性 地震能量密集值
Abstract活动断层对泥石流的形成和活动影响巨大,过去由于断层自身的隐伏特点,对断层活动规律及其对地表影响的差异缺乏研究,从而使代表地球内营力作用的活动断层对泥石流影响难以量化评估,使得目前在泥石流危险性评价中如何准确、合理的考虑活动断层的影响存在困难。本文针对现有活动断层评估方法的不足,选取川西龙门山断裂带和鲜水河断裂带为主要试验区,结合重大地震事件,以活动断层—重大地震(主震和余震)—诱发滑坡—形成泥石流的灾害链过程为线索;根据震后的余震事件沿断层的空间分布,采用半无限空间中的能量密度方法计算并分析试验区地震能量密集值的空间分布,借助活动断层影响强度的衰减模型,建立量化评估活动断层影响的理论方法;以重大地震事件后的泥石流、滑坡灾害点的实际分布情况对活动断层影响的空间效应进行对比验证;最终形成量化评估活动断层影响的技术体系,为泥石流灾害定量化评估和山区经济活动建设选址提供理论和方法支持。通过本论文的研究,取得了如下成果:(1)以半无限空间中的能量密度公式为基础,建立了基于地震能量密集值的活动断层评估方法,并且能量密集值可以直接作为界定活动断层影响的指标。同时,能量密集值在沿着断层走向以及垂直断层方向上的空间衰减规律解释了活动断层的多普勒效应、上下盘效应(长、短轴效应),也间接的验证了地表破裂带的空间分布位置和范围。(2)统计了汶川MS8.0级地震之后的余震以及滑坡、泥石流等山地灾害沿龙门山断裂带(右旋走滑兼逆冲)的空间分布范围与衰减规律,通过对比鲜水河断裂带(左旋走滑)的余震与滑坡、泥石流灾害分布,分析了活动断层的致灾效应:断层活动触发的地震(包括主震和余震)快速释放的能量与不同的地表形态(如地形、高差、地层岩性等)产生的耦合作用是形成山地灾害区域分异规律的外部环境因素。(3)以龙门山断裂带和鲜水河断裂带这两个试验区内余震以及滑坡泥石流灾害点的空间分布与衰减规律对基于能量密集值的活动断层影响评估方法进行了验证,提出了以地震能量密集值的概率分布曲线为基础,建立活动断层影响的评估标准和影响范围的划分依据,以汶川地震灾区的汶川、北川、青川三个剖面为例计算了龙门山中央断裂的影响范围和分级标准。(4)将量化评估活动断层的方法引入典型区的危险性区划中,采用活动断层能量密集值、地层岩性、坡度、地形起伏度、地表烈度、地震动峰值加速度、年降雨量变差系数、月降雨量变差系数、土体利用类型等9个指标开展了汶川地震灾区的泥石流滑坡危险性区划,结果表明在危险区域辨识度方面新方法要优于传统方法,四川省泥石流危险性区划也验证了新方法的可行性。论文的创新点在于:(1)以半无限空间中的能量密度公式为基础,建立了基于地震能量密集值的活动断层评估方法,合理的解释了活动断层影响的空间效应,突破了一般统计方法的局限。(2)以地震能量密集值的衰减过程为基础,结合不同的地表形态因子开展泥石流区划试验,结果显示,能量密集值法可以在一定程度上替代地质背景环境指标,从而实现资料缺乏地区泥石流危险性的快速评估。
Other AbstractActive faults impact debris flow greatly; but so far there is no method available for quantitatively assessing their influence. The dissertation devotes to build a theoretic method of quantifying the action of active faults based on studies of the processe-chain of fault-earthquake and aftershocks-landslide and/or debris flow, using the data of fault belts of Longmenshan and Xianshuihe in west Sichuan. Spatial distribution of seismic energy is calculated by the semi-infinite half-space method; then the decay of fault influence is determined. Based on this a quantified assessment of fault influence is proposed and tested by comparison with the distribution of hazardous events along the faults after intense earthquakes. The major conclusions are as follows:(1) The seismic energy bounds the fault influence and the energy distribution explains the Doppler effect and hanging-wall effect, and also the distribution of surface fractures;(2) Comparison of spatial distribution and decay of landslide and debris flow after the Wenchuan earthquake along the right-lateral strike-slip faults of Longmenshan and those along the sinistral strike-slip faults of Xianshuihe indicates that the hazards are resulted from the coupling of seismic energy release and the topographic factors (such as landform, elevation, and lithology). (3) Assessment criterions and influence divisions of active fault are made on basis of probability distribution of seismic energy, which have been confirmed by case studies in the fault zones of Longmenshan and Xianshuihe. Gradation criterions are proposed for the central faults of Longmenshan based on three profiles of Wenchuan, Qingchuan and Beichuan.(4) A quantitative method is proposed for assessing debris flows and landslides in Wenchuan earthquake area, combining the calculated fault energy and other 8 indicators: lithology, slope, topographic relief, seismic intensity, The peak ground acceleration, annual precipitation variation coefficient, monthly precipitation variation coefficient, land-use type. The result proves superior to the conventional methods. The applicability and validity of the method are also confirmed by danger division of debris flows in Sichuan.Novelty of the study relies in that it quantitatively assess the fault influence using seismic energy and explains the spatial effects of the influence, which is greatly superior to the statistical approaches. In addition, seismic energy is used in danger assessment, which is particularly helpful for quick assessment of debris flow in areas lack of data.
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7068
Collection山地灾害与地表过程重点实验室
Recommended Citation
GB/T 7714
苏鹏程. 活动断层对泥石流的影响及其量化评估研究[D]. 北京. 中国科学院研究生院,2013.
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