The 2013 Lushan earthquake: Implications for seismic hazards posed by the Range Front blind thrust in the Sichuan Basin, China
The 2013 Lushan earthquake: Implications for seismic hazards posed by the Range Front blind thrust in the Sichuan Basin, China
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DOI：
10.1130/g35809.1
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发表时间：
2014-10
期刊：
影响因子：
5.8
通讯作者：
Maomao Wang;D. Jia;J. Shaw;J. Hubbard;A. Plesch;Yiquan Li;Bao‐Fen Liu
中科院分区：
文献类型：
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作者：
Maomao Wang;D. Jia;J. Shaw;J. Hubbard;A. Plesch;Yiquan Li;Bao‐Fen Liu
逆冲断层和逆断层在世界各地的会聚板块边缘造成了重大的地震危险，但由于其断裂的复杂性，往往涉及多个沿走向和垂直堆叠的断层段，因此很难研究。2013年芦山6.6级地震就是这种复杂性的一个例证，它破坏了龙门山南部的一个盲冲断层，龙门山与中国四川盆地西部接壤。这一事件发生在2008年汶川7.9级地震震中以南80公里处。汶川地震在两条平行的断层展布带上产生了地表破裂，这两条断层展布带是彭官断层和北川断层。相反，芦山地震是由位于汶川断裂下盘的岭前盲冲断层（RFBT）中的斜坡产生的。我们利用地震反射剖面、石油威尔斯井和重新定位的地震活动来构建这个叠瓦状断层系统的三维模型。我们的模型表明，2013年芦山地震破裂<10%的RFBT，这沿着龙门山山脉前缘延伸沿着250 km，进入四川盆地西部。对RFBT断层沿着走向上方构造中生长地层的分析显示，第四纪活动的证据清晰，并将中更新世限制在断层上两个位置的当前滑动速率。涉及RFBT的单段和多段断层破裂情景表明，可能发生影响人口稠密的四川盆地西部的大地震（M7.8）。评估这种复杂的逆冲系统所造成的危害，发生在收敛的边缘世界各地，需要地下断层段的特性，可以独立地与地质和地震的断层活动的证据。
Thrust and reverse faults pose significant earthquake hazards in convergent plate margins around the world, but have proven difficult to study given the complex nature of their ruptures, which often involve multiple along-strike and vertically stacked fault segments. The 2013 Mw 6.6 Lushan earthquake exemplified this complexity, rupturing a blind thrust fault in the southern Longmen Shan, which border the western Sichuan Basin in China. This event occurred 80 km south of the epicenter of the destructive 2008 Mw 7.9 Wenchuan earthquake. The Wenchuan earthquake produced surface ruptures on two parallel fault splays, the Pengguan and Beichuan faults. In contrast, the Lushan earthquake was generated by a ramp in the Range Front blind thrust (RFBT), which is in the footwall of the Wenchuan rupture. We use seismic reflection profiles, petroleum wells, and relocated seismicity to construct a three-dimensional model of this imbricated fault system. Our model illustrates that the 2013 Lushan earthquake ruptured <10% of the RFBT, which extends for 250 km along the Longmen Shan range front and into the western Sichuan Basin. Analysis of growth strata in structures above the RFBT fault along strike shows clear evidence of Quaternary activity and constrains the middle Pleistocene to current slip rate at two locations on the fault. Single segment and multisegment fault rupture scenarios involving the RFBT suggest the potential for large earthquakes (M7.8) that would affect the densely populated western Sichuan Basin. Assessing the hazards posed by such complex thrust systems, which occur in convergent margins worldwide, requires subsurface characterization of fault segments that can be independently associated with geologic and seismologic evidence of fault activity.