Joint inversion of InSAR, local seismic and teleseismic data sets for the rupture process of the 2020 Mw 6.3 Yutian earthquake and its implications
Joint inversion of InSAR, local seismic and teleseismic data sets for the rupture process of the 2020 Mw 6.3 Yutian earthquake and its implications
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DOI：
10.1016/j.tecto.2022.229289
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发表时间：
2022-03
期刊：
影响因子：
2.9
通讯作者：
Zhengsong Chen;Lei Yi;Jun Luo;Kezhen Zuo
中科院分区：
文献类型：
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作者：
Zhengsong Chen;Lei Yi;Jun Luo;Kezhen Zuo
2020年6月25日，玉田县发生6.3级地震。通过联合反演当地地震和远震波形数据以及干涉合成孔径雷达（InSAR）视距位移数据，解析了本次地震的时空破裂特征，从而更好地研究和理解区域地壳伸展机制。反演结果表明，此次地震沿一条主陡坡破裂，断裂深度在4.1 ~ 13.3 km范围内，最大滑移量约0.9 m。破裂锋面最初围绕震源传播，然后单方面向北传播。整个过程持续约8 s，释放的总标量地震矩为3.2 × 1018Nm （Mw 6.3）。基于能量的平均应力降在1.9 ~ 3.0 MPa之间。辐射效率估计为10.0 ~ 15.8%，相对较低，说明大部分累积应变能在破裂过程中耗散。考虑到震源的消散破裂和火山西缘西倾的诱发断层，认为此次地震可能与附近的新生代火山有关。西昆仑地块的西向运动和昆仑—柴达木地块的东向运动是玉田地区ew向地壳伸展的主要原因。我们认为2020年的正断层地震主要是由于昆仑-柴达木地块东移速度不同所致。此外，根据同震库仑应力相互作用分析，2008年Mw 7.1地震、2012年Mw 6.2地震和2014年Mw 6.9地震对2020年Mw 6.3地震的震源产生了较小的库仑应力扰动，表明以前的玉田地震对2020年事件的触发作用有限。
On 25 June 2020, a Mw 6.3 earthquake struck Yutian county. The earthquake nucleated on a normal fault in the northwestern Tibetan Plateau. Through jointly inverting local seismic and teleseismic waveform data as well as Interferometric Synthetic Aperture Radar (InSAR) Line-of-Sight (LOS) displacement data, the spatiotemporal rupture properties of this earthquake were resolved to investigate and better understand regional crustal extension mechanisms. Inversion results show that this event ruptured along one main asperity concentrated within a depth range of 4.1–13.3 km with a maximum slip of ~0.9 m. The rupture front propagated initially around the hypocenter and then unilaterally toward the north. The whole process lasted approximately 8 s and released a total scalar seismic moment of 3.2 × 1018Nm (Mw 6.3). The energy-based average stress drop was estimated in the range of 1.9–3.0 MPa. The radiation efficiency was estimated to be 10.0–15.8%, which is relatively low, demonstrating that most of the accumulated strain energy dissipated during rupturing. We suggest that the earthquake was possibly related to the nearby Cenozoic volcano in consideration of the dissipated rupture of the source and the west-dipping causative fault located on the western edge of the volcano. Both the westward motion of the western Kunlun block and the eastward motion of the Kunlun-Qaidam block were responsible for the EW-trending crustal extension in the Yutian district. We supposed that the 2020 normal faulting earthquake was primarily attributed to the different velocities of the Kunlun-Qaidam block moving eastward. Additionally, according to an analysis of coseismic Coulomb stress interactions, the previous 2008 Mw 7.1, 2012 Mw 6.2, and 2014 Mw 6.9 Yutian earthquakes contribute small Coulomb stress disturbance on the hypocenter of the 2020 Mw 6.3 Yutian earthquake which suggest that previous Yutian earthquakes have a limited effect on triggering the 2020 event.