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利用断裂带上的低b值识别凹凸体方法的探讨——以龙门山断裂带和鲜水河断裂带为例
引用本文:李正芳,周本刚.利用断裂带上的低b值识别凹凸体方法的探讨——以龙门山断裂带和鲜水河断裂带为例[J].震灾防御技术,2014,9(2):213-225.
作者姓名:李正芳  周本刚
作者单位:中国地震局地质研究所,活动构造与火山实验室,北京 100029;中国地震局地质研究所,活动构造与火山实验室,北京 100029
基金项目:科技支撑项目“特大地震危险区识别及危险性评价方法研究(2012BAK15B01)”和“中国地震局地质研究所中央级公益性科研院所基本科研业务专项(IGCEA1310)”共同资助
摘    要:本文对龙门山断裂带和鲜水河断裂带上1970年以来记录的小震数据进行了收集、整理和分析,采用基于Matlab平台的Zmap软件,去除了断裂带上的丛集数据和余震,划定了有效地震数据的时间和震级范围,通过最大似然法求取了断裂带所在区域的b值分布图。基于b值大小与应力高低成反比的原理,通过断裂带上低b值区识别凹凸体的位置。就龙门山断裂带,通过低b值区识别出的凹凸体的位置与汶川地震发生的起始破裂位置和极震区的位置基本保持一致;而鲜水河断裂带由于受到小震数据的限制,部分段缺失b值分布,但整条断裂带仍可清晰识别出凹凸体位置,且1725年以来的历史强震和1970年以来5级以上的历史地震基本上都位于此区域。断裂带的实例分析结果证明,利用小震数据通过最大似然法计算b值分布图,其相对低b值区与历年强震发生的位置存在较大的相关性,为验证利用低b值区识别凹凸体方法的可行性和实用性提供了有力的证据。

关 键 词:龙门山断裂带  汶川地震  鲜水河断裂带  b    凹凸体
收稿时间:8/5/2013 12:00:00 AM

Asperity Identification Based on Low b-value: Application to the Longmenshan and Xianshuihe Fault Zone
Li Zhengfang and Zhou Bengang.Asperity Identification Based on Low b-value: Application to the Longmenshan and Xianshuihe Fault Zone[J].Technology for Earthquake Disaster Prevention,2014,9(2):213-225.
Authors:Li Zhengfang and Zhou Bengang
Institution:Key Laboratory of Active Tectonics and Volcano, Institute of Geology,China Earthquake Administration, Beijing 100029, China;Key Laboratory of Active Tectonics and Volcano, Institute of Geology,China Earthquake Administration, Beijing 100029, China
Abstract:In this paper, we collected, collated and analyzed small earthquakes recorded since 1970 in the Longmen Shan fault zone and the Xianshuihe fault zone. By using zmap software from the Matlab platform, we removed cluster data and aftershocks, selected small earthquake data and magnitude range, at last, we made the b-value map by the maximum likelihood method. Taking low or high b values as an indication of high or low applied shear stresses, we identified asperity position in the fault zone. The asperity position in the Longmenshan fault zone identified in our study is consistent with the initial rupture position before the Wenchuan earthquake happened. Due to the limitations of small earthquake data distribution, we can not identify asperity position along the whole Xianshuihe fault, but we still can identify four asperity in the middle and northern segment in the Xianshuihe fault, where historical strong earthquake since 1725 and historical earthquake which was larger than five since 1970 occurred.
Keywords:Longmenshan fault zone  Wenchuan earthquake  Xianshuihe fault zone  b value  Asperity
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