甘肃夏河断裂新活动的发现 |
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引用本文: | 张波,王爱国,袁道阳,文亚猛,王维桐,秦满忠,何文贵.甘肃夏河断裂新活动的发现[J].地震学报,2020,42(5):629-644. |
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作者姓名: | 张波 王爱国 袁道阳 文亚猛 王维桐 秦满忠 何文贵 |
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作者单位: | 1.中国北京 100029 中国地震局地质研究所 |
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基金项目: | 地震科技星火计划(XH19045Y)和中国地震局地震预测研究所基本科研业务费专项(2020IESLZ02,2018IESLZ02)共同资助 |
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摘 要: | 2019年10月28日甘肃夏河MS5.7地震发生于临潭—宕昌断裂与西秦岭北缘断裂之间,震中周边断裂的发育情况不明,断裂研究程度低,且无明确的地表断裂与该地震相关。本文通过遥感解译和野外调查,完善了震中周边断裂即临潭—宕昌断裂、夏河断裂东段和达麦—合作断裂的几何展布图像和新活动特征,结合小震精定位和震源机制,综合分析并构建了夏河地震的发震构造模型。研究结果显示:夏河地震的周边断裂包括两条已知、但研究程度不高的西秦岭北缘断裂和临潭—宕昌断裂,以及仅标绘在地质图上、活动未知的夏河断裂和达麦—合作断裂;首次发现了夏河断裂东段的新活动,活动性质兼具左旋走滑和向北逆冲,前人基于小震定位判定的发震断层(走向312°,倾向42°,倾角48°)可能是夏河断裂东段派生的一条隐伏分支,该分支在平面上与夏河断裂东段呈小角度斜交(夹角22°),在深部归并到夏河断裂,滑动方向(滑动角48°)与夏河断裂东段的活动性质(兼具逆冲和左旋)一致。夏河断裂东段在构造上可能归属于临潭—宕昌断裂西段,是西秦岭北缘断裂正花状构造的组成部分,2019年夏河MS5.7地震代表临潭—宕昌断裂西段的构造活动。
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关 键 词: | 2019年甘肃夏河MS5.7地震 发震构造 夏河断裂 临潭—宕昌断裂 西秦岭北缘断裂 |
收稿时间: | 2020-01-14 |
Discovery of new activity of Xiahe fault in Gansu:Discussion on seismogenic structure of the 2019 Xiahe MS5.7 earthquake |
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Institution: | 1.Institute of Geology,China Earthquake Administration, Beijing 100029,China2.Gansu Lanzhou Geophysics National Observation and Research Station,Lanzhou 730000,China3.School of Earth Sciences,Lanzhou University,Lanzhou 730000,China |
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Abstract: | On October 28, 2019, a magnitude 5.7 earthquake struck the Xiahe county, Gansu Province. This event was located between the Lintan-Dangchang fault and West Qinling fault, where surface faults were poorly mapped and studied, and there was no fault directly related to the Xiahe MS5.7 earthquake. In this paper, through the remote sensing interpretation and field investigation, the geometric pattern and new activity of geological faults around the Xiahe earthquake epicenter were studied preliminarily. Combined with the relocated small earthquakes and the focal mechanism solutions, the seismotectonic model of the Xiahe earthquake was built up and comprehensively analyzed. The results are as follows. First, the surrounding faults of the Xiahe earthquake include two well-known but poorly-studied faults (the West Qinling fault and Lintan-Dangchang fault) and two poorly-known faults (the Xiahe fault and Damai-Hezuo fault) that were only mapped on the geological map. Second, this work has acquired more detailed geometric pattern and new activity of the Lintan-Dangchang fault, the east segment of the Xiahe fault, and the Damai-Hezuo fault, and we have discovered Holocene activity of the Xiahe fault for the first time, it is of both left-lateral strike-slip and northward reverse-slip. Third, the seismogenic fault plane (the strike, dip direction and dip angle are 312°, 42° and 48°, respectively) determined by previous studies based on earthquake sequence relocation is likely to be one hidden fault derived from the east segment of Xiahe fault, the hidden fault is at a small angle (22°) to the east segment of Xiahe fault, and merges with Xiahe fault in the deep earth, slip direction of the hidden fault (rake is 48°) agrees well with the slip senses (with both left-lateral slip and reverse slip) of the east segment of the Xiahe fault. The east segment of the Xiahe fault may be structurally part of the west segment of the Lintan-Dangchang fault and is part of the positive flower structure of the West Qinling fault, and the Xiahe MS5.7 earthquake in 2019 represents the tectonic activity of the west segment of the Lintan-Dangchang fault. |
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