Detailed mapping of the surface rupture of the 12 February 2014 Yutian M_s7.3 earthquake, Altyn Tagh fault, Xinjiang, China
Detailed mapping of the surface rupture of the 12 February 2014 Yutian M_s7.3 earthquake, Altyn Tagh fault, Xinjiang, China
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2014年2月12日中国新疆阿尔金断裂带于田M_s7.3地震地表破裂详细测绘
DOI：
10.1007/s11430-020-9673-6
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Li Tao
中科院分区：
文献类型：
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作者：
Yuan Zhaode;Liu-Zeng Jing;Li Xue;Xu Jing;Yao Wenqian;Han Longfei;Li Tao
大比例尺精细填图对揭示强震破裂特征和机制具有重要作用。西藏中西部地区地处偏远，海拔较高，对大地震地表破裂的研究相对较少。基于高分辨率无人机（UAV）摄影，绘制了2014年于田7.3级地震的同震地表破裂图。沿着西部阿尔金断裂系统，地震沿着南绍尔科尔断层（南段S1）、绍尔科尔断层（中段S2）和阿什库勒断层（北方S3）产生了约37公里的地表破裂。S1断面有一条16 km长的地表破裂，平均左旋偏移量为52±25 cm，最大偏移量约为90 cm; S3断面有一条14.2 km长的地表破裂，平均左旋偏移量为36±21 cm，最大偏移量约为84 cm。对5308条裂缝进行统计，得出南段裂缝平均宽度为85±71 cm，最大宽度约为700 cm;中段裂缝平均宽度为39±21 cm，最大宽度约为243 cm;北方裂缝平均宽度为61±44 cm，最大宽度约为340 cm。此外，断裂带的平均累积开口沿南段为沿着3.4±2.9 m，最大值约为17 m;沿中段为沿着4.3±3.6 m，最大值约为13 m;沿北方为沿着1.7±1.6 m，最大值约为6 m。明显地，平均裂缝宽度和累积张开度沿着断层向弯曲和台阶沿着减小。对全球走滑地震地表破裂分布的综合研究表明，断层几何形状复杂部位（如弯曲、台阶和断层分叉）附近的破裂带比沿着直线段的破裂带宽，表明断层几何形状对地表破裂带宽度有明显的控制作用。Xor Kol和South Xor Kol断层交叉处的广泛裂缝可能表明，伸展状态更可能产生分布的断层外变形，这为断层动态破裂的数值模拟提供了观测约束。玉田地震除了产生同震地表破裂外，还在缓坡冲积扇上产生了大量的重力滑动。扇体下含水盐层的摩擦效率可降低滑动门槛值，触发地表震动失稳。这些分布的变形和重力驱动的滑动反映了破裂传播和断层几何形状之间的耦合，并表明破裂可能在穿过一个台阶后沿着阿什库勒断层向两个方向传播。因此，同震地表破裂的研究为动态破裂过程提供了重要的观测约束。
Large-scale detailed mapping plays a key role in revealing the rupture characteristics and mechanisms of strong earthquakes. Relatively few studies have been performed on the surface ruptures of large earthquakes in central and western Tibet due to its remote nature and high elevation. Based on high-resolution unmanned aerial vehicle (UAV) photography, we mapped the coseismic surface rupture of the 2014 Yutian M_s7.3 earthquake. Along the western Altyn Tagh fault system, the earthquake produced ~37 km of surface rupture along the South Xor Kol fault (southern section S1), Xor Kol fault (central section S2) and Ashikule fault (northern section S3). Section S1 has a 16-km-long surface rupture with an average sinistral offset of 52±25 cm and a maximum offset of ~90 cm, while section S3 has a 14.2-km-long surface rupture with an average sinistral offset of 36±21 cm and a maximum offset of ~84 cm. A compilation of 5308 cracks yields an average crack width along the southern section of 85±71 cm and a maximum width of ~700 cm; the average width along the central section is 39±21 cm, and the maximum width is 243 cm; and the average width along the northern section is 61±44 cm with a maximum of ~340 cm. In addition, the average cumulative opening across rupture zone is 3.4±2.9 m along the southern section, with a maximum of ~17 m; 4.3±3.6 m along the central section, with a maximum of ~13 m; and 1.7±1.6 m along the northern section, with a maximum of ~6 m. Evidently, the average crack width and cumulative opening decrease towards bends and steps along the fault. A global synthesis of surface rupture distributions corresponding to strike-slip earthquakes indicates that the rupture zone is wider near the complex parts of fault geometries (such as bends, steps and fault bifurcations) than along straight sections, suggesting that the fault geometry has an obvious control on the surface rupture width. The widespread cracks at the intersection between the Xor Kol and South Xor Kol faults may indicate that an extensional regime is more likely to produce distributed offfault deformation, which provides an observational constraint for the numerical simulation of dynamic rupture on a fault. In addition to coseismic surface rupture, the Yutian earthquake also produced a large number of gravity-driven slides on alluvial fans with gentle slopes. The friction efficiency of the water-bearing salt layer beneath fans could decrease the sliding threshold and trigger instability under surface shaking. These distributed deformations and gravity-driven slides reflect the coupling between the rupture propagation and fault geometry and indicate that the rupture may have propagated in two directions along the Ashikule fault after passing through a step. Therefore, the investigation of coseismic surface rupture provides important observational constraints on the dynamic rupture process.