Source parameters of the 2016 Menyuan earthquake in the northeastern Tibetan Plateau determined from regional seismic waveforms and InSAR measurements
Source parameters of the 2016 Menyuan earthquake in the northeastern Tibetan Plateau determined from regional seismic waveforms and InSAR measurements
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DOI：
10.1016/j.jseaes.2018.02.009
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发表时间：
2018-06-01
影响因子：
3
通讯作者：
Shan, Xinjian
中科院分区：
文献类型：
--
作者：
Liu, Yunhua;Zhang, Guohong;Shan, Xinjian
2016年1月21日，青海省门源县发生6.4级地震。最近的已知断层是冷龙岭 (LLL) 断层，位于震中以北约 7 公里处。该断裂晚第四纪以来主要表现为左行走滑运动。但震源机制表明这是一次逆冲地震，与众所周知的LLL断层走滑特征不同。本研究利用中国数字地震台网（CDSN）记录的宽带区域地震波形，通过频域和时域多步反演确定震源机制和主节面。结果表明，破裂持续时间短，在震后0-2秒内，破裂沿断层向上扩展。基于这些断层参数，我们然后使用 InSAR 数据求解断层面上的可变滑移分布。应用三段断层模型模拟了北部LLL断层的弧形结构，获得了断层面上详细的滑移分布。反演结果显示，最大滑移为0.43 m，平均滑移角为78.8°，震级为Mw 6.0，震源深度为9.38 km。结合地质结构和反演结果，推测此次地震是由位于LLL断裂北侧的弧形次生断裂引发的。次生断层与LLL断层一起形成正常的花状结构。主要的 LLL 断层几乎垂直延伸到基岩中，两条断层之间的岩石形成凸起的断块。因此，我们推断，这次地震是新构造运动的表现，在青藏高原向西北方向推压的压剪作用下，隆起的断块进一步抬升。
On January 21st, 2016, a Ms 6.4 earthquake hit Menyuan County, Qinghai province, China. The nearest known fault is the Leng Long Ling (LLL) fault which is located approximately 7 km north of the epicenter. This fault has mainly shown sinistral strike-slip movement since the late Quaternary Period. However, the focal mechanism indicates that it is a thrust earthquake, which is different from the well-known strike-slip feature of the LLL fault. In this study, we determined the focal mechanism and primary nodal plane through multi-step inversions in the frequency and time domain by using the broadband regional seismic waveforms recorded by the China Digital Seismic Network (CDSN). Our results show that the rupture duration was short, within 0-2 s after the earthquake, and the rupture expanded upwards along the fault plane. Based on these fault parameters, we then solve for variable slip distribution on the fault plane using the InSAR data. We applied a three-segment fault model to simulate the arc-shaped structure of the northern LLL fault, and obtained a detailed slip distribution on the fault plane. The inversion results show that the maximum slip is 0.43 m, and the average slip angle is 78.8 degrees, with a magnitude of Mw 6.0 and a focal depth of 9.38 km. With the geological structure and the inversion results taken into consideration, it can be suggested that this earthquake was caused by the arc-shaped secondary fault located at the north side of the LLL fault. The secondary fault, together with the LLL fault, forms a normal flower structure. The main LLL fault extends almost vertically into the base rock and the rocks between the two faults form a bulging fault block. Therefore, we infer that this earthquake is the manifestation of a neotectonics movement, in which the bulging fault block is lifted further up under the compresso-shear action caused by the Tibetan Plateau pushing towards the northwest direction.