GNSS-Constrained Rupture Kinematics of the 2022 Mw 6.7 Luding, China, Earthquake: Directivity Pulse during the Asymmetrical Bilateral Rupture

IF 2.6 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Gang Liu, Bin Zhao, Rui Xu, Xuejun Qiao, Chengli Liu, Yu Li, Mu Lin, Xinyu Zhao, Zhaosheng Nie, Wei Xiong, Rongxin Fang, Qi Wang
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Abstract

Abstract Impulse motion characterized by a large amplitude in the fault-normal direction can be observed at near-fault strong motion sites during strike-slip earthquakes. The large pulse, which always causes high intensity and stronger damage to structures close to faults, is usually attributed to the directivity effect of rupture propagating along strike and the proximity to the fault. We present an analysis of such a large directivity pulse captured by the near-fault high-rate Global Navigation Satellite System (GNSS) during the 2022 Mw 6.7 Luding, China, earthquake—the largest event ever observed by space geodesy on the seismically active Xianshuihe fault in the eastern Tibetan Plateau. We invert the displacement waveforms and offsets derived from the continuous and campaign GNSS for the rupture kinematics. The inferred slip model reveals a rupture zone of 30 km in length above 15 km depth along the Moxi segment, yielding a seismic moment of 1.1×1019 N·m and a source duration of 13 s. The high-rate GNSS (hrGNSS) waveforms suggest an asymmetric bilateral rupture: most slips with long rise time are concentrated on the southern part of the ruptured fault, whereas a short-duration pulse-like slip rate with low final slip propagates during the northward rupture. We found that the directivity pulse observed by the nearest hrGNSS site is controlled primarily by the sharp pulse-like slip rate and rapid rupture velocity approximating the local S-wave velocity. Along with additional local amplification, this large directivity pulse may be responsible for the heavy damage in Moxi town close to the northern ruptured fault.
2022年中国泸定6.7 Mw地震的gnss约束破裂运动学:不对称双边破裂期间的指向性脉冲
在走滑地震中,在断层附近的强震场址可以观测到断层-正法向的大振幅脉冲运动。大脉冲总是对断层附近的构造造成高强度和更强的破坏,这通常归因于破裂沿走向传播的指向性效应和靠近断层。本文对近断层高速率全球导航卫星系统(GNSS)在2022年中国泸定6.7 Mw地震中捕获的如此大的指向性脉冲进行了分析,这是在青藏高原东部地震活跃的鲜水河断层上空间大地测量观测到的最大事件。我们反演了从连续和运动GNSS中得到的位移波形和偏移量,用于破裂运动学。推导出的滑动模型显示,沿磨溪段在15 km深度以上存在一个长度为30 km的破裂带,产生的地震矩为1.1×1019 N·m,震源持续时间为13 s。高速率GNSS (hrGNSS)波形显示了不对称的双边破裂:大多数上升时间长的滑动集中在破裂断层的南部,而在北部破裂期间传播的是短持续时间的脉冲状滑动率,最终滑动量低。我们发现,最近的hrGNSS站点观测到的指向性脉冲主要由接近当地s波速度的尖锐脉冲样滑移率和快速破裂速度控制。加上额外的局部放大,这种大的指向性脉冲可能是造成靠近北部破裂断层的磨溪镇严重破坏的原因。
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来源期刊
Seismological Research Letters
Seismological Research Letters 地学-地球化学与地球物理
CiteScore
6.60
自引率
12.10%
发文量
239
审稿时长
3 months
期刊介绍: Information not localized
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