Rupture process models of the Yangbi and Maduo earthquakes that struck the eastern Tibetan Plateau in May 2021
Rupture process models of the Yangbi and Maduo earthquakes that struck the eastern Tibetan Plateau in May 2021
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2021年5月青藏高原东部漾濞地震和玛多地震破裂过程模型
DOI：
10.1016/j.scib.2021.11.009
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发表时间：
2021
期刊：
影响因子：
18.9
通讯作者：
Zhenxing Yao
中科院分区：
文献类型：
--
作者：
Wei-Min Wang;Jiankun He;Xun Wang;Yun Zhou;Jinlai Hao;Lian-Feng Zhao;Zhenxing Yao
一辆M6。北京时间2021年5月21日21时48分（2021年5月21日13时48分37秒），云南省大理州漾濞县发生4级地震。此后不久，世界标准时间 2021 年 5 月 22 日 2:04（2021-05-21 18:04:13 世界标准时间），一架 M7。青海省果洛地区玛豆县发生4级地震。这两次地震分别发生在青藏高原东部东南边缘和高海拔腹地（图1a），均造成人员伤亡和财产损失，引发地震应急响应。不同地点在5 h内相继发生强震，表明在印度与欧亚大陆板块碰撞汇聚作用下，青藏高原发生了持续的构造运动和强烈的地震活动[3]。地壳运动观测揭示了青藏高原东部沿东喜马拉雅构造构造轴发生顺时针旋转变形[2, 4]。此外，将构造和历史地震数据与数值模拟相结合的研究表明，青藏高原内地壳物质向东流动的剪切效应导致青藏高原北部活跃的左旋走滑断裂和南部的右旋走滑断裂[1,3,5]。这两起事件的震源机制（图S1在线）表明，两次地震都是由于当前地壳变形引起的应变而发生的，这与上述青藏高原的变形模式是一致的。因此，研究青藏高原作为地球上最大的构造变形区及其周边的变形机制是当前地球科学研究的一个重点。然而，两种主要的板内变形模型“块体模型”和“连续体模型”的主要观点并不能完美地解释青藏高原观测到的变形和地震活动[2]，这表明需要进一步的工作。在此背景下，我们通过地震波形和同震变形数据联合反演，建立了这两次强震的时空震源破裂过程模型，从而揭示了相应的构造运动特征。这些发现可以为青藏高原变形机制提供新的认识和约束。此外，所提出的震源模型作为地震学研究的基本组成部分，可以为地震减灾和地震风险评估提供科学依据。我们通过地震研究机构联合研究机构（IRIS）数据管理中心下载了全球分布的数字地震台站采集的波形记录，快速反演这两次强震的震源机制和震源破裂过程。在初步结果的基础上，我们收集了额外的观测数据，构建了有限断层模型，并通过联合反演准确地获得了相应的源过程。研究漾濞震源过程的数据为区域三分量波形（从中国国家数字地震台网下载）、远场P和SH波形以及欧洲航天局（ESA）Sentinel卫星获得的同震形变数据（干涉合成孔径雷达，InSAR），其雷达图像覆盖震前和震后震源区（网上表S1）。为了研究玛多震源过程，由于缺乏近源地震记录，我们使用了从 ESA Sentinel 获得的远场 P 和 SH 波形以及同震视线 (LOS) 位移……
An M6. 4 earthquake struck Yangbi County, Dali Prefecture, Yunnan Province, on May 21, 2021, at 21: 48 Beijing Time (2021-05-21 13: 48: 37 UTC). Soon thereafter, at 2: 04 UTC on May 22, 2021 (2021-05-21 18: 04: 13 UTC), an M7. 4 earthquake struck Madou County, Guoluo Prefecture, Qinghai Province. These two earthquakes occurred in the southeastern edge and in high-altitude hinterland of the eastern Tibetan Plateau respectively (Fig. 1a), and both caused human casualties and property damage, triggering earthquake emergency response efforts. The occurrence of strong earthquakes at different sites within 5 h of each other indicates continuous tectonic movements and violent seismic activity on the Tibetan Plateau under the collisional convergence between the Indian and Eurasian continental plates [3]. Observations of crustal motion expose clockwise rotational deformation in the eastern Tibetan Plateau along the axis of the eastern Himalayan syntaxis [2, 4]. Furthermore, studies combining tectonic and historical seismic data with numerical simulations reveal that the shear effect of the eastward flow of crustal material within the Tibetan Plateau leads to active sinistral strike-slip faulting in the northern part of the plateau and dextral strike-slip faulting in the south [1, 3, 5]. The source mechanisms of these two events (Fig. S1 online) suggest that both earthquakes occurred in response to the strain induced by the current crustal deformation, which is consistent with the above deformation pattern of the Tibetan Plateau. Accordingly, studying the deformation mechanisms in and around the Tibetan Plateau, being the largest zone of tectonic deformation on Earth, is a major focus of ongoing geoscience research. Nevertheless, the main views of the two predominant intraplate deformation models, the ‘‘block model” and the ‘‘continuum model”, cannot perfectly explain the observed deformation and seismic activity across the Tibetan Plateau [2], indicating that further work is needed. In this context, we developed models of the spatiotemporal source rupture processes of these two strong earthquakes by jointly inverting seismic waveforms and coseismic deformation data, thereby revealing the corresponding tectonic motion characteristics. These findings can provide new insights into and constraints on the deformation mechanisms on the Tibetan Plateau. Additionally, the proposed source models, as fundamental components of seismological research, can provide a scientific basis for seismic hazard mitigation and earthquake risk assessment.We downloaded waveform records acquired at globally distributed digital seismic stations through the Incorporated Research Institutions for Seismology (IRIS) Data Management Center to rapidly invert the focal mechanisms and source rupture processes of these two strong earthquakes. Based on the preliminary results, we gathered additional observations to construct a finite fault model and accurately obtained the corresponding source processes by a joint inversion. The data used to study the Yangbi earthquake source process are regional three-component waveforms (downloaded from the China National Digital Seismic Network), far-field P and SH waveforms, and coseismic deformation data (interferometric synthetic aperture radar, InSAR) obtained from the European Space Agency (ESA) Sentinel satellites, whose radar images cover the pre-and postearthquake source area (Table S1 online). To study the Maduo earthquake source process, due to the lack of near-source seismic records, we used far-field P and SH waveforms and coseismic line-of-sight (LOS) displacements obtained from the ESA Sentinel …