2020年尼玛<i>M</i><sub>W</sub>6.3地震同震及震后断层滑动特征

刘洋; 张宇; 温扬茂; 杨九元

doi:10.19975/j.dqyxx.2022-078

2020年尼玛M_W6.3地震同震及震后断层滑动特征

doi: 10.19975/j.dqyxx.2022-078

刘洋^{1, 2, 3, ,},
张宇¹,
温扬茂^{1, 2, 3},
杨九元¹

1.
武汉大学测绘学院，武汉 430079
2.
武汉大学地球空间环境与大地测量教育部重点实验室，武汉 430079
3.
武汉大学自然资源部地球物理大地测量重点实验室，武汉 430079

基金项目: 国家自然科学基金资助项目（41874011，41974004，41404007）

详细信息

通讯作者:
刘洋（1984-），男，副教授，主要从事InSAR数据处理与地学解释的研究. E-mail：Yang.Liu@sgg.whu.edu.cn

中图分类号: P228, P315
计量
- 文章访问数: 84
- HTML全文浏览量: 26
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- 被引次数: 0
出版历程
- 收稿日期: 2022-12-11
- 录用日期: 2023-01-15
- 修回日期: 2023-01-11
- 网络出版日期: 2023-02-02

Coseismic and postseismic fault slip characteristics of the 2020 M_W6.3 Nima earthquake

Liu Yang^{1, 2, 3
, ,},
Zhang Yu¹,
Wen Yangmao^{1, 2, 3},
Yang Jiuyuan¹

1.
School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China
2.
Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, Wuhan University, Wuhan 430079, China
3.
Key Laboratory of Geophysical Geodesy, Ministry of Natural Resources, Wuhan University, Wuhan 430079, China

Funds: Supported by the National Natural Science Foundation of China (Grant Nos. 41874011, 41974004, 41404007)

摘要

摘要: 2020年尼玛M_W6.3地震发生在青藏高原羌塘块体依布茶卡地堑北部. 震中区域地质构造、地形地貌复杂，近场地面观测台站、数据较少. 合成孔径雷达干涉测量（Interferometric Synthetic Aperture Radar, InSAR）技术具有全天侯、大范围、高空间分辨率等监测优势，能够弥补近场地面形变观测的不足. 然而，已有研究对该次地震发震断层、同震及震后断层滑动特征的观点存在差异，且仅采用运动学模型提取震后断层余滑特征. 本文利用哨兵1号（Sentinel-1）卫星升、降轨合成孔径雷达（Synthetic Aperture Radar, SAR）影像和差分干涉测量技术提取该次地震不同视角的同震形变场，基于弹性半空间位错模型反演地震同震断层几何及滑动分布，采用应力驱动的震后余滑模型对震后断层滑动进行建模分析，并且探讨了地震发震断层及断裂带摩擦属性特征. 结果表明，升、降轨InSAR同震形变场在震中区域连续光滑、整体呈NNE-SSW走向，断层南东侧区域形变均较为显著且沿视线向以下降为主. 同震断层破裂以正断为主，兼有左旋走滑分量，走向角为31.43º，倾角为45.79º，同震断层滑动主要位于地下3.58～10.75 km，最大滑动量为1.33 m，矩震级为M_W6.33. 应力驱动的震后余滑模型能够较好地解释尼玛M_W6.3地震近6个月的InSAR震后形变场，震后余滑主要发生在同震断层显著滑动区域南西段的上侧、下侧及南西侧，最大值为47.2 cm. 尼玛M_W6.3地震发震断层可能为位于依布茶卡—日干配错断裂中部、倾向SEE的正断层，发震断裂带摩擦属性可能非均匀.
- 尼玛M_W6.3地震 /
- 同震 /
- 震后 /
- 断层滑动 /
- 应力驱动
Abstract: The 2020 M_W6.3 Nima earthquake occurred in the northern Yibug Caka graben on the Qiangtang Block of the Tibetan Plateau. The epicentral area has complex geological structures, topography, and geomorphology, and there are few near-field ground observation stations and data. Interferometric Synthetic Aperture Radar (InSAR) has all-weather, wide ranging and high spatial resolution monitoring advantages, which can make up for the shortage of near-field ground deformation observations. However, previous studies have obtained different viewpoints regarding the seismogenic fault and coseismic and postseismic fault slip characteristics of this event. In addition, only the kinematic model has been used to extract the postseismic fault afterslip characteristics. In this study, we used ascending and descending Sentinel-1 Synthetic Aperture Radar (SAR) images and differential interferometry technology to extract the coseismic deformation fields at different viewing angles. The coseismic fault geometry and slip distribution were then inverted based on an elastic half-space dislocation model. The stress-driven postseismic afterslip model was used to model and analyze the postseismic fault slip. Finally, the earthquake seismogenic fault and the friction property characteristics of seismogenic fault zone were discussed. The ascending and descending InSAR coseismic deformation fields were continuous and smooth around the epicenter, trending NNE-SSW overall. The deformation on the southeastern side of the fault was relatively significant, and mainly decreased along the line-of-sight direction. The coseismic fault rupture was mainly normal, with a sinistral strike-slip component. The strike angle was 31.43°, and the dip angle was 45.79°. The coseismic fault slip was mainly located at 3.58-10.75 km underground, with a maximum slip of 1.33 m, and the moment magnitude was M_W6.33. The stress-driven postseismic afterslip model could better explain the almost six-month InSAR postseismic deformation field of this event. The postseismic afterslip mainly occurred on the upper, lower and southwestern sides of the southwestern segment of the significant slip area of coseismic fault, with a maximum afterslip of 47.2 cm. The seismogenic fault of this event might be a normal fault located in the middle of the Yibug Caka-Riganpei Co fault and dipping SEE, and the friction property of the seismogenic fault zone might be uneven.
- M_W6.3 Nima earthquake /
- coseismic /
- postseismic /
- fault slip /
- stress-driven

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图 1 （a）尼玛M_W6.3地震区域的主要构造特征，黑色实线表示断裂，红色震源球表示来自美国地质调查局（USGS）、全球矩心矩张量（GCMT）的地震震源机制解，蓝色方框表示SAR观测范围；（b）黑色方框表示图（a）中显示的区域

Figure 1. (a) Major tectonic characteristics of the M_W6.3 Nima earthquake zone. Black solid lines represent faults. Red beach balls represent focal mechanisms from the United States Geological Survey (USGS) and Global Centroid Moment Tensor (GCMT). Blue boxes represent the Synthetic Aperture Radar (SAR) observation coverages. (b) Black box indicates the region shown in (a)

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图 2 尼玛M_W6.3地震InSAR同震形变场、基于同震断层滑动分布模型的拟合及残差形变场，（a）、（d）、（g）对应于升轨012；（b）、（e）、（h）对应于降轨121；（c）、（f）、（i）对应于降轨019. 蓝色实线表示本文确定的同震断层滑动分布模型地表迹线

Figure 2. Interferometric Synthetic Aperture Radar (InSAR) coseismic deformation field of the M_W6.3 Nima earthquake, as well as fitted and residual deformation fields based on the coseismic fault slip distribution model. (a), (d), and (g) are for ascending track 012; (b), (e), and (h) are for descending track 121; and (c), (f), and (i) are for descending track 019. Blue lines denote the surface traces of the coseismic fault slip distribution model determined in this study

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图 3 （a）同震断层滑动分布，绿色箭头表示滑动方向；（b）同震断层滑动分布误差

Figure 3. (a) Coseismic fault slip distribution. Green arrows denote the slip direction; (b) Coseismic fault slip distribution error

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图 4 （a）尼玛M_W6.3地震InSAR震后形变场（数据来自于Yang et al., 2022），黑色、紫色实线分别表示几何模型1、2的地表迹线，虚线方框表示计算拟合残差的空间范围；基于震后断层余滑分布模型的拟合及残差形变场，（b）、（c）对应于几何模型1，（d）、（e）对应于几何模型2

Figure 4. (a) InSAR postseismic deformation field of the M_W6.3 Nima earthquake (data from Yang et al., 2022). Black and purple solid lines denote the surface traces of geometric modes 1 and 2, respectively. Dashed box denotes the spatial coverage of the fitted residual calculation. Fitted and residual deformation fields based on the postseismic fault afterslip distribution model. (b) and (c) are for geometric mode 1; (d) and (e) are for geometric mode 2

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图 5 不同震后余滑模型参数对应的拟合残差RMS. （a）几何模型1（$ \varphi =0.2 $）；（b）几何模型2（$ \varphi =0.4 $）. 黑色圆圈表示较优模型参数

Figure 5. Root Mean Square (RMS) values of fitted residual corresponding to different postseismic afterslip model parameters. (a) is for geometric mode 1 ($ \varphi =0.2 $); (b) is for geometric mode 2 ($ \varphi =0.4 $). Black circles denote the preferred model parameters

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图 6 应力驱动的震后断层余滑分布. （a）几何模型1；（b）几何模型2. 空白区域表示滑动分布集中后的同震断层显著滑动区域

Figure 6. Stress-driven postseismic fault afterslip distribution. (a) is for geometric mode 1; (b) is for geometric mode 2. Blank areas denote the significant slip areas of coseismic fault after concentrating the slip distribution

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表 1 尼玛M_W6.3地震震源参数

Table 1. Source parameters of the M_W6.3 Nima earthquake

	经度/纬度/(º)	长度/km	顶深/底深/km	走向/倾角/(º)	滑动角/滑动量/[(º)/m]	地震矩/（10¹⁸ N·m）/M_W
USGS	86.86/33.14	－	11.5^a)	20/61	−91/－	－/6.27
GCMT	86.87/33.10	－	16.8^a)	10/48	−88/－	－/6.4
Gao等(2022)^b)	－	13.1	－	28.8/49.4	−78.6/1.2	－/6.28
Hu等(2022)^b)	－	12.6	－	31.3/51.6	−70.5/2.63	－/6.3
冀宗童等(2021)^b)	－	12.3	－	28.4/48.3	−81.34/1.06	3.59/6.3
李承涛等(2021)^b)	－	13.2	－	30.41/49.52	−71.27/1.47	－/6.3
Li等(2021)^b)	－	－	－	28/48	−87/－	－/6.4
梁世川等(2022)^b)	－	12.38	－	207/33.1	−96.31/2	－/－
Yang等(2022)^b)	－	13.2	－	30/48.3	−80.2/1.2	－/6.3
本研究^c)	86.827/33.209	12.81	4.68/9.32	31.43/45.79	−75.77/1.22	3.03/6.29
本研究^c)	0.001/0.001	0.11	0.07/0.06	0.42/0.42	0.92/0.04	0.02/0.002
a) 矩心深度；b) 均匀滑动模型结果；c) 基于均匀滑动模型反演确定的震源参数，下面行的数值表示上面行对应参数值的误差

下载: 导出CSV

表 2 干涉像对参数

Table 2. Parameters of the interferometric pairs

轨道	升、降轨	主影像日期	辅影像日期	时间基线/d	空间基线/m
012	升轨	2020-07-18	2020-07-30	12	−84.9
121	降轨	2020-07-14	2020-07-26	12	108.8
019	降轨	2020-07-13	2020-07-25	12	43.9

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