SEISMOGENIC STRUCTURE OF THE Ms7.0 EARTHQUAKE ON AUGUST 8, 2017 IN JIUZHAIGOU, SICHUAN
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摘要: 2017年8月8日21时19分，四川阿坝州九寨沟县发生7.0级地震，震中位于巴颜喀拉块体东边界虎牙断裂和东昆仑断裂带东段塔藏断裂交汇区域，地震构造背景较为复杂。地震导致了房屋和道路破坏、滑坡崩塌。根据高分辨率卫星影像解译、阶地坎变形的测量和测年数据得到：塔藏断裂东段晚第四纪以来以左旋走滑为主，兼逆分量，水平滑动速率为2.7~4.1 mm/yr，垂直滑动速率为0.56~0.6 mm/yr。结合此次地震的主余震分布、主震震源机制解等综合结果，初步建立了三维发震构造模型，分析认为此次地震属于走滑型地震，主破裂倾角57°~77°，发震断层可能是塔藏断裂的一条分支，是青藏高原块体向东推挤的一次地震事件。基于历史地震、活动断裂和形变观测方面的研究，巴颜喀拉块体具备显著的强震构造背景，对于该块体边界带周缘的强震活动和变形需要继续关注。
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关键词:
- 九寨沟Ms7.0级地震 /
- 塔藏断裂东段 /
- 活动断裂 /
- 发震构造 /
- 巴颜喀拉块体
Abstract: An Ms7.0 earthquake struck Jiuzhaigou county at 9:19 pm on August 8, 2017 in Aba Prefecture of Sichuan Province. The epicenter was located in the intersection area of the Huya fault on the east boundary of the Bayan Har block and the Tazang fault on the east section of the East Kunlun fault, with complicated seismotectonic settings. This earthquake caused damages to houses and roads, and landslides collapsed. According to the data of high-resolution satellite image interpretation, the measurement data of tectonic deformation and dating data, it shows that the east section of the Tazang fault has been dominated by left-lateral strike-slip accompanied with thrust faulting; the horizontal sliding rate is about 2.7~4.1 mm/yr, and the vertical sliding rate is about 0.56~0.6 mm/yr. Combined with the distribution of major earthquake and aftershocks and the results of major earthquake source mechanism solution, a three-dimensional seismic structure model is established. The analysis reveals that this earthquake belongs to strike-slip earthquake with the main rupture angle of 57°~77°. It was caused by the eastward push of the Qinghai-Tibet Plateau mass, and the seismogenic fault may be a branch of the Tazang fault. According to the study of historical earthquakes, active faults and deformation observation, the Bayan Kala block has significant strong earthquake tectonic background, and it is necessary to continue to pay attention to the seismic activity and deformation of the boundary of the block. -
图 1 研究区断裂及余震分布图
ATF—阿尔金断裂带；HF—海原断裂带；KTF—昆仑断裂带；LMF—龙门山断裂带；JLF—嘉黎断裂带；RRF—红河断裂带；TZF—塔藏断裂；LRBF—龙日坝断裂；MJF—岷江断裂；BLGF—白龙江断裂；GGS-DSF—光盖山-迭山断裂；HYF—虎牙断裂
Figure 1. Distribution map of regional faults and aftershocks in the study area
图 2 地震精定位及余震分布图(据IGP-CEA)
Figure 2. Precise location of the earthquake and distribution map of aftershocks
图 3 下黄寨遥感解译及断层剖面
a-高分一号影像三维可视化解译（图中箭头指示断层位置）；b-断层剖面；c-断层剖面示意图
Figure 3. GF-1 remote sensing image and fault profile of Xiahuangzhai
图 4 神仙池附近遥感解译及断错地貌
a-神仙池附近高分一号影像三维可视化；b-断错地貌照片；c-地层褶皱照片
Figure 4. GF-1 remote sensing image and fault profile of Shenxianchi area
图 5 漳扎镇附近遥感解译
a-漳扎镇一带高分一号三维可视化；b-彭布地貌照片；c-荷叶地貌照片；d-彭布断层剖面
Figure 5. GF-1 remote sensing image and landform near Zhangzha Town
图 6 草坡沟西北断错地貌
a-Google earth影像；b-山脊位错；c-断层陡坎
Figure 6. Dislocation landform in northwestern Caopogou
图 7 若也得附近冲洪积的断错
a-Google earth影像；b-高分一号影像；c-地貌位错图；d-T2阶断层陡坎地实测剖面；e-采样剖面洪积扇位错
Figure 7. Dislocation of alluvial fan near Ruoyedei area
图 8 唐寨无人机航拍与DGPS测量
a-唐寨断错地貌；b-无人机航拍图；c-DGPS实测地形；d-T2阶断层陡坎地实测剖面；e-T3阶地断层陡坎实测剖面；g、f-采样剖面图
Figure 8. UAV aerial image and DGPS measurement of Tangzhai
表 1 四川九寨沟7.0级地震的震源机制解参数
Table 1. Focal mechanism solutions of the Jiuzhaigou Ms7.0 earthquake
资料来源 断层节面Ⅰ 断层节面Ⅱ 震中 震源深度
/km震级 走向/° 倾角/° 滑动角/° 走向/° 倾角/° 滑动角/° CENC 326 62 15 64 77 151 103.82°E 33.20°N 20 M7.0 Global-CMT 150 78 13 242 77 150 103.90°E 33.21°N 14.9 Ms6.5 IGP-CEA 153 84 33 246 57 173 103.85°E 33.19°N 13.5 Mw6.5 
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表 2 AMS 14C样品测年结果
Table 2. The dating reults of AMS14C samples
样品编号 实验室样品编号 采样深度/m 13C/12C 样品岩性 年龄结果/a BP JZG-C-01 440594 1.8 25.4% 碳屑 2450±30 JZG-C-02 446948 1.2 24.9% 碳屑 5110±30 JZG-C-03 440593 1.0 26.9% 碳屑 1470±30 注：样品由美国BETA实验室测试
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