SEISMOLOGY AND GEOLOGY ›› 2018, Vol. 40 ›› Issue (5): 980-998.DOI: 10.3969/j.issn.0253-4967.2018.05.003

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LATE QUATERNARY TECTONIC DEFORMATION AROUND THE HUJIATAI ANTICLINE ALONG THE EAST SEGMENT OF THE FODONGMIAO-HONGYAZI FAULT, NORTHERN QILIAN SHAN: AN INSIGHT ON THE SEISMOGENIC PATTERN OF 1609 HONGYAZI M7 1/4 EARTHQUAKE

YANG Hai-bo, YANG Xiao-ping, HUANG Xiong-nan, HU Zong-kai   

  1. Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China
  • Received:2017-11-05 Revised:2018-03-02 Online:2018-10-20 Published:2018-11-29

祁连山北缘佛洞庙-红崖子断裂胡家台背斜区构造变形——1609年M7 1/4红崖子地震构造样式

杨海波, 杨晓平, 黄雄南, 胡宗凯   

  1. 中国地震局地质研究所, 活动构造与火山重点实验室, 北京 100029
  • 通讯作者: 杨晓平,研究员,E-mail:yangxiaoping-1@163.com
  • 作者简介:杨海波,男,1989年生,2016年于中国地震局地质研究所获构造地质学硕士学位,在读博士研究生,主要研究活动构造,E-mail:yanghaibo2015@gmail.com。
  • 基金资助:
    国家自然科学基金(41572195)和中国地震活动断层探察:南北地震带北段(20140823)共同资助

Abstract: The Fodongmiao-Hongyazi Fault (FHF)is one of the most active faults of the northern Qilian thrust fault zone. The 1609 Hongyazi M7 1/4 earthquake occurred on the east segment of the FHF, an area with a complex geometry at the Mayinghe River site. The seismogenic pattern of this earthquake revealed by complex surface ruptures remains unclear. In this paper, we focus on active tectonic deformation around the Hujiatai anticline (HA)in the Mayinghe River site. Combining with topographic survey via dGPS across deformed terraces and alluvial fans, a field survey of the geological section across the HA, the characteristics of the active fold and several sub-faults were constrained. Meanwhile, combined with the seismic reflection profiles passing through the anticline, the correspondence relationship between surface expressions of this tectonic and the deep structure was discussed. According to our research, the HA is a result of northward propagation of the range-front thrust fault F1. At the same time, a thrust fault F2 with dextral strike-slip motion and a thrust fault F4 were formed on the east side and north side of the HA, respectively. These two active faults accommodated local deformation. Trench results and 14C dating reveal that the 1609 Hongyazi M7 1/4 earthquake ruptured the T1 terrace in the Huangcaoba site. Combined with previous field investigations and literature about the 1609 Hongyazi earthquake, we suggest that this earthquake occurred on the range-front fault F1, and the depth of the hypocenter may be about 8~22km.

Key words: Mayinghe River, Hujiatai anticline, northern Qilian thrust fault zone, Hongyazi historical earthquake, seismogenic pattern

摘要: 佛洞庙-红崖子断裂是祁连山北缘断裂带中构造活跃的断裂之一,断裂东段胡家台背斜区发育多种类型的构造,且部分断裂被证实在1609年M7 1/4红崖子地震中发生破裂,但复杂的地表破裂特征所反映的深部发震构造样式还不清楚。因此,文中选取了佛洞庙-红崖子断裂东段胡家台背斜区及附近多组活动构造为研究对象,利用差分GPS对变形的河流阶地、洪积扇等进行测量,并对背斜核部出露的地质剖面进行了实测,获得了不同类型构造的活动特征。结合已有穿过背斜的地震反射剖面,构建构造地貌与深部结构之间的对应关系,从而探讨地震的发震构造样式。研究表明,背斜区发育了胡家台背斜以及多条逆断裂或逆-走滑断裂,背斜为祁连山北麓逆断裂向N逆冲扩展形成,并伴随形成背斜东侧1条逆冲兼右旋走滑断裂和北侧另1条逆断裂,这些逆断裂或逆-走滑断裂为调节局部构造应变差异而产生。黄草坝探槽结果表明,1609年红崖子地震破裂了黄草坝T1阶地;再结合前人关于此次地震的野外考察和文献资料考证,认为1609年M7 1/4红崖子地震发生在祁连山山麓逆断裂上,地震至少破裂了NWW向山前F1、胡家台背斜东侧NNW向F2和EW向F3断裂,震源深度可能为8~22km。

关键词: 马营河, 胡家台背斜, 祁连山北麓断裂, 红崖子地震, 发震构造样式

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