Discussion on Seismogenic Structure of Ninglang MS5.5 Earthquake on January 2, 2022
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摘要: 2022年1月2日云南省宁蒗县发生MS5.5地震,地震位于川滇边界处泸沽湖附近。历史上该地区曾多次发生5.5级左右的中强地震,震区构造复杂,NW向和NE向断裂展布相互交织,构成棋盘格状。据野外地质调查,震中区附近NW向永宁断裂和NE向日古鲁-岩瓦断裂具有明显的晚更新世活动迹象,同时对永宁新生代构造盆地和新生界具有明显的控制作用。根据泸沽湖西侧地质钻孔推测永宁盆地内尚发育1条与永宁断裂平行的NW向隐伏断层。地震震源机制解、同震位移场、地震烈度分布特征及地震现场破坏调查结果表明,此次地震与NW向永宁活动断裂密切相关。Abstract: On January 2, 2022, an MS5.5 earthquake occurred in Ninglang County, Yunnan Province, near Lugu Lake at the junction of Sichuan and Yunnan. This area has been many medium-strong earthquakes of about 5.5 magnitude in history, and is an earthquake prone area in Northwest Yunnan, The structure of the earthquake area is complex, and two groups of NW and NE faults are intertwined to form a checkerboard grid. According to the field geological survey, the NW trending Yongning fault and the NE trending Rilu Yanwa fault near the epicenter have obvious signs of late Pleistocene active faults, and have obvious control over the Cenozoic tectonic basin and the Cenozoic of Yongning. Geological drilling on the west side of Lugu Lake speculated that there is still a NW hidden fautl parallel to the Yongning fault in the Yongning Basin. According to the analysis of the seismic source mechanism solution, the coseismic displacement field, the distribution characteristics of the seismic intensity and the results of the earthquake site destruction survey, it is believed that the earthquake is closely related to the Yongning active fault in the NW direction.
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Key words:
- Ninglang earthquake /
- Yongning fault /
- Seismogenic structure /
- Focal mechanism
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表 1 钻孔主要地层
Table 1. Main stratum of borehone
地层名称 地层特征 坡积层 褐黄、褐红、褐灰色,结构松散,黏性土为主,山麓斜坡地带含碎石、砾石,表层有植物根系 淤泥层 深灰色,软塑,湿。土质软,表现为高压缩性、强黏着感,层中含少量有机质,偶夹粉土薄层,为沼泽沉积相 泥炭土 灰黑色,可塑,湿。土层中含大量有机质、腐殖质,质轻,易压缩,韧性差,夹灰、黄灰色可塑黏土层,为湖积沉积相 碎石土层 褐黄色,中密,饱和。砾石含量约35%,分布不均匀,大量黏性土和角砾充填,为残积相 玄武岩 深灰色,岩芯裂隙发育,岩质坚硬,钻进困难。岩芯表现为破碎,多呈碎石、碎块状,上部局部地带有全风化残积层分布 表 2 不同机构给出的震源机制解得到的中心震源机制解标准差
Table 2. Standard deviation of central focal mechanism solution obtained from focal mechanism solutions given by different mechanisms
序号 震源机制解走向、倾角
和滑动角/(°)机构或作者 作为初始解得到的中心
震源机制解走向、倾角
和滑动角/(°)作为初始解得到的
标准差S/(°)震源机制解与其他机构震源机制解的最小空间旋转角/(°) 1 183,41,−50 亥姆霍兹波茨坦中心(GFZ) 198.7,64.9,−26.2 30.3 30.3 2 198,63,−37 郭祥云等 198.7,64.9,−26.3 30.3 10.6 3 206,71,−9 韩立波等 198.7,64.9,−26.3 30.3 17.1 4 177,69,−71 中国地震台网中心 198.7,66.0,−153.7 95.3 41.3 5 196,55,−30 雷兴林 198.7,64.9,−26.3 30.3 10.5 6 210,73,21 中国地震科学实验场
大理中心198.7,64.9,−26.7 30.3 45.1 7 293,70,170 赵韬 300.5,66.3,−152.5 30.3 35.5 -
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