| 基于GNSS与InSAR约束的九寨沟MS7.0地震滑动模型及其库仑应力研究 |
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| 引用本文： | 陈威,乔学军,刘刚,熊维,贾治革,李瑜,王阅兵,游新兆,龙锋.基于GNSS与InSAR约束的九寨沟MS7.0地震滑动模型及其库仑应力研究[J].地球物理学报,2018,61(5):2122-2132. |
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| 作者姓名： | 陈威 乔学军 刘刚 熊维 贾治革 李瑜 王阅兵 游新兆 龙锋 |
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| 作者单位： | 1. 中国地震局地震研究所, 地震大地测量重点实验室, 武汉 430071;2. 地壳运动监测工程研究中心, 北京 100036;3. 四川省地震局, 成都 610041 |
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| 基金项目： | 中国地震局星火计划（XH17023Y）和国家自然科学基金（41704009，41704101）资助. |
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| 摘 要： | 2017年8月8日的九寨沟MS7.0地震发生在岷江断裂、塔藏断裂及虎牙断裂交汇地区，地处青藏高原东北部的川甘交界地区，位于巴颜喀拉地块的东缘，地质构造复杂，对于九寨沟地震震中位置和发震断层的确定，存在不同意见.本文利用GNSS及升降轨InSAR观测，在获取九寨沟地震同震形变场的基础上，基于均匀弹性半无限位错模型，联合反演了发震断层的滑动分布模型，并计算了同震库仑应力变化.InSAR同震形变场显示，视线向最大沉降量和抬升量分别为0.21 m和0.16 m，形变场长轴为NW向，形变主要集中在断层西侧.距震中40 km和65 km的九寨和松潘两县，水平向的GNSS同震位移分别达14.31 mm和8.22 mm.联合GNSS和InSAR同震形变场反演得到的滑动分布主要集中在沿走向5~33 km，倾向2~20 km的范围内，平均滑动量为0.18 m，最大滑动量为0.91 m.发震断层长40 km，宽30 km，走向155°，倾角81°，滑动角-9.56°.同震位移场及滑移分布模型表明此次地震为一次左旋走滑为主的地震事件，地震破裂并未完全到达地表，与虎牙断裂北段的几何产状和运动学性质更为接近，结合精定位余震的分布，我们确定虎牙断裂北段为此次地震的发震断层，震中位于北纬33.25°，东经103.82°，震源深度10.86 km，矩震量为7.754×1018 Nm，相应的矩震级为MW6.5，与美国地调局和哈佛大学给出的震源机制解基本一致.同震库仑应力导致了虎牙断裂北段延长线的东北和西南两端应力增强，其中塔藏断裂的罗叉段和马磨段未来强震的危险性值得关注.
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| 关 键 词： | 2017九寨沟地震 GNSS InSAR 同震滑动分布模型 同震库仑应力 |
| 收稿时间： | 2017-11-05 |
Study on the coseismic slip model and Coulomb stress of the 2017 Jiuzhaigou MS7.0 earthquake constrained by GNSS and InSAR measurements |
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| CHEN Wei,QIAO XueJun,LIU Gang,XIONG Wei,JIA ZhiGe,LI Yu,WANG YueBing,YOU XinZhao,LONG Feng.Study on the coseismic slip model and Coulomb stress of the 2017 Jiuzhaigou MS7.0 earthquake constrained by GNSS and InSAR measurements[J].Chinese Journal of Geophysics,2018,61(5):2122-2132. |
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| Authors: | CHEN Wei QIAO XueJun LIU Gang XIONG Wei JIA ZhiGe LI Yu WANG YueBing YOU XinZhao LONG Feng |
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| Institution: | 1. Key Laboratory of Earthquake Geodesy, Institute of Seismology, China Earthquake Administration, Wuhan 430071, China;2. National Earthquake Infrastructure Service, Beijing 100036, China;3. Sichuan Earthquake Administration, Chengdu 610041, China |
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| Abstract: | The Jiuzhaigou MS7.0 earthquake of August 8, 2017 occurred at the conjunction of the Minjiang, Tazang and Huya faults, the border area between Sichuan and Gansu provinces as well as the northeastern part of the Tibetan Plateau where the tectonics is very complex. There exists a certain controversy about the accurate location of the epicenter and the seismogenic fault for this earthquake. Based on the coseismic deformation field obtained from GNSS and InSAR observations, we inverted for the characteristics of coseismic slip model, spatial distribution and the coseismic Coulomb stress changes using a homogeneous elastic half-space model. The features of coseismic deformation derived from InSAR and GNSS show that this event is dominated by left-lateral strike-slip. The maximum and minimum displacements are about 0.16 m and -0.21 m, respectively, along LOS with the whole deformation field is in the NW direction which is concentrated on the west of the fault. The GNSS horizontal deformation at Jiuzhaigou county and Songpan county, which are of 40 km and 65 km away from the epicenter, are 14.31 mm and 8.22 mm, respectively. Slips are mainly distributed in 5~33 km along strike and 2~20 km along down-dip direction. The maximum and average displacements are 0.91 m and 0.18 m, respectively. The seismic rupture did not fully reach the ground surface. The fault plane is 40 km long and 30 km wide with strike angle 155°,dip angle 81° and rake angle -9.56°. These features are consistent with the kinematics and geometry of the northern section of the Huya fault, so we concluded that the northern section of the Huya fault is the seismogenic fault of the Jiuzhaigou earthquake. Results derived from geodetic measurements indicate the epicenter of this event is located at E103.82°,N33.25° with focal depth of 10.86 km and the moment released about 7.754×1018 Nm, corresponding to a magnitude of MW6.5 which is consistent with that from USGS and GCMT. The coseismic Coulomb stress changes have enhanced the stress on the northeast and southwest of northward extension part of the Huya fault,but fewer aftershocks were recorded on this section, indicating that the seismic risk of the Mamo and Luocha segments of the Tazang fault is increasing. |
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| Keywords: | 2017 Jiuzhaigou earthquake GNSS InSAR Coseismic slip model Coseismic Coulomb stress |
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