Late Holocene activity and historical earthquakes of the Qiongxi thrust fault system in the southern Longmen Shan fold-and-thrust belt, eastern Tibetan Plateau
Late Holocene activity and historical earthquakes of the Qiongxi thrust fault system in the southern Longmen Shan fold-and-thrust belt, eastern Tibetan Plateau
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DOI：
10.1016/j.tecto.2012.08.019
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发表时间：
2013-01
期刊：
影响因子：
2.9
通讯作者：
Maomao Wang;D. Jia;A. Lin;L. Shen;G. Rao;Yiquan Li
中科院分区：
文献类型：
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作者：
Maomao Wang;D. Jia;A. Lin;L. Shen;G. Rao;Yiquan Li
2008年5月12日汶川地震（Mw7.9）在青藏高原东缘龙门山褶皱冲断带产生了一条沿着长285 km的地表破裂带。汶川地震没有破裂到西南龙门山，沿沿着没有大的古地震或历史地震的证据。地震反射剖面和野外调查表明，拉萨市南部50公里长的琼西逆冲断层（QTF）目前处于活动状态。QTF由三个向西倾斜的斜坡段组成，这些斜坡段上覆有断层弯曲褶皱，这些褶皱源于区域拆离作用，该拆离作用将缩短作用从山区带转移到四川盆地。海沟调查，再加上地震反射剖面和放射性碳结果的解释，表明最近的地表破裂地震发生在明末到清朝，公元1600年和1800年之间的QTF。此外，地震反射剖面和地形分析表明，存在一个微妙的地形，所产生的扭结带迁移折叠上方约5公里深的断层弯曲。这些研究结果证实，QTF是一个重要的地震危险性，它应该被纳入目前的区域地震危险性模型的人口稠密的四川盆地。
The 12 May 2008 Wenchuan earthquake (Mw7.9) generated a 285-km-long surface rupture zone along the Longmen Shan fold-and-thrust belt (LSFTB) on the eastern margin of Tibetan Plateau. The Wenchuan earthquake did not rupture into the southwestern Longmen Shan, along which there is no evidence for large paleo- or historical earthquakes. Seismic reflection profiles and field investigations reveal that the 50-km-long Qiongxi thrust fault (QTF) of the southern LSFTB is currently active. The QTF consists of three west-dipping ramp segments overlain by fault-bend folds rooted in a regional detachment that transfers shortening from the mountain belt into the Sichuan basin. Trench investigations, coupled with interpretations of seismic reflection profiles and radiocarbon results, show that a recent surface-rupturing earthquake occurred on the QTF during the Late Ming to Qing Dynasty, between AD 1600 and 1800. In addition, seismic reflection profile and topographic analysis indicate the presence of a subtle topographic, produced by kink-band migration folding above a fault bend at about 5km depth. These findings confirm that the QTF is a significant seismic hazard, and that it should be incorporated into current regional seismic hazard models for the densely populated Sichuan basin.