| 2017年西藏米林MS6.9地震余震序列重定位和b值时空分布特征 |
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| 引用本文： | 韩佳东,杨建思,王伟平.2017年西藏米林MS6.9地震余震序列重定位和b值时空分布特征[J].地震学报,2019,41(2):169-180. |
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| 作者姓名： | 韩佳东 杨建思 王伟平 |
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| 作者单位： | 中国北京 100081 中国地震局地球物理研究所;中国北京 100081 中国地震局地球物理研究所;中国北京 100081 中国地震局地球物理研究所 |
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| 基金项目： | 国家自然科学基金项目（41874075）资助 |
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| 摘 要： | 本文采用双差定位方法对2017年西藏米林MS6.9地震的余震序列进行重定位，获得了较准确的余震空间分布。在此基础上，计算了米林地震震源区的b值空间分布，并结合前人资料研究了米林地震前后的b值变化。重定位结果显示:米林地震余震序列呈NW?SE向分布，主要分布在雅鲁藏布江大拐弯缝合带和比鲁构造岩片的北东边界，震源深度集中于3—20 km范围内。b值时间分布显示:米林地震震前震源区的b值降低，表明震前震源区存在较强的应力积累；地震后震源区的b值呈现跳跃式上升，反映出震源区应力释放，同时随时间的推移，b值逐渐趋于稳定。米林地震震源区的b值在0.52—1.35范围内变化，15 km深度以上b值在东、西方向上存在差异，15 km以下在东北、南西方向上存在差异，由此推测不同的b值分布与地下的结构特征有关，浅层的b值变化与震源区的破裂程度相关，深部变化则反映了不同构造单元的岩性差异。
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| 关 键 词： | 米林 M S 6.9地震 b 值 双差定位 余震空间分布 |
| 收稿时间： | 2018-06-06 |
Relocation of the aftershock sequence of Milin MS6.9 earthquake in 2007 and spatio-temporal variation characteristics of b-value |
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| Institution: | Institute of Geophysics， China Earthquake Administration， Beijing 100081， China |
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| Abstract: | The aftershock sequence of the Milin MS6.9 earthquake in Tibet in 2017 are relocated by double-difference algorithm in this paper. Based on the relocated results, the spatial distribution of b-value in the source region of Milin earthquake is obtained. Combining historical b-value data from previous researches, the temporal distribution of b-value in the studied area is also obtained. The relocation results show that the aftershock sequence of the Milin earthquake are distributed in NE?SE direction along the NE boundary of Indus-Yarlung Tsangpo big-turned suture and Bilu tectonic slice, most aftershocks are concentrated in 3?20 km depth. The temporal distribution of b-value shows before Milin earthquake b-value is lower than that in the year of 2008, indicating that the stress accumulation in the studied area is strong before Milin earthquake. After Milin earthquake, there was a step-rise of b-value, showing the releases of stress, and b-value tended to stable. b-value ranges in 0.52?1.35 in the source region of Milin earthquake, the b-value variation above the depth of 15 km is distributed along the east-west direction, and below 15 km along the NE?SW direction. Therefore, it is deduced that different b-value distribution represents different structure characteristics, i.e., the b-value variation of the shallow area is related to the degree of rupture in the source region, and the b-value variation of deep area reflects the lithology difference of different tectonic units. |
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