SEISMOLOGY AND EGOLOGY ›› 2022, Vol. 44 ›› Issue (1): 220-237.DOI: 10.3969/j.issn.0253-4967.2022.01.014

• Research paper • Previous Articles     Next Articles


XU Fang1)(), LU Ren-qi1),*(), WANG Shuai2), JIANG Guo-yan3), LONG Feng4), WANG Xiao-shan5), SU Peng1), LIU Guan-shen1)   

  1. 1) State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
    2) College of Geomatics Science and Technology, Nanjing Tech University, Nanjing 211800, China
    3) School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China
    4) Sichuan Earthquake Agency, Chengdu 610041, China
    5) Hebei Earthquake Agency, Shijiazhuang 050021, China
  • Received:2021-01-15 Revised:2021-04-27 Online:2022-02-20 Published:2022-04-20
  • Contact: LU Ren-qi


徐芳1)(), 鲁人齐1),*(), 王帅2), 江国焰3), 龙锋4), 王晓山5), 苏鹏1), 刘冠伸1)   

  1. 1)中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029
    2)南京工业大学, 测绘科学与技术学院, 南京 211800
    3)武汉大学, 测绘学院, 武汉 430079
    4)四川省地震局, 成都 610041
    5)河北省地震局, 石家庄 050021
  • 通讯作者: 鲁人齐
  • 作者简介:徐芳, 女, 1997年生, 2019年于合肥工业大学获地质学学士学位, 现为中国地震局地质研究所构造地质学专业在读硕士研究生, 主要从事活动构造分析与三维建模研究, E-mail:
  • 基金资助:


On February 3, 2020, an earthquake with a magnitude MS5.1 occurred in Qingbaijiang District, Chengdu City, Sichuan Province. The epicenter is located in the north segment of the Longquan Shan fault zone in the western Sichuan Basin. This fault zone locates in the forebulge of the foreland thrust belt of the Longmen Shan fault zone in the southeast margin of Tibetan plateau and is the east boundary of the western Sichuan foreland basin at the same time, so it has special tectonic significance. There are two branch faults in the north segment of Longquan Shan fault zone, which are distributed on the east and west sides, respectively, and the epicenter distance is almost similar to the two faults. At present, the seismogenic fault, earthquake genesis and dynamic source of the earthquake are not clear. As this earthquake is a moderate earthquake event, it is usually very uncertain to interpret it with structural geological or seismological data alone. Therefore, this study attempts to carry out a comprehensive study on the Qingbaijiang MS5.1 earthquake by performing cross fusion of multi-disciplinary data, adopting the multi-constraint method from geophysics, seismology and geodesy, and combining with structural geology and fault related fold theory. We collected three seismic reflection profiles located in the north segment of the fault zone to reveal the basic structural characteristics underground. The detachment layer in the middle-lower Triassic Jialingjiang-Leikoupo formation is developed at the depth of 4~6km below the anticline, and two obvious opposite thrust faults are developed on the two wings of the anticline, which are breakthrough fault-propagation fold deformation. The east branch thrust fault gradually rises from the detachment layer of Leikoupo formation to the surface, and the west branch thrust fault is exposed on the surface and connected with the detachment layer downward. The waveform data recorded by 14 fixed stations within 150km from the epicenter of Sichuan seismic network are studied and collected. The focal depth, focal mechanism and moment magnitude of the earthquake are obtained by using CAP waveform inversion method. The focal depth is 5km, indicating that the earthquake is related to shallow fault activity, the focal mechanism is 18°/32°/100° for nodal plane I and 186°/59°/84° for nodal plane Ⅱ, the moment magnitude is 4.64. Using the travel time data of P and S seismic phases, the Qingbaijiang earthquake sequence is relocated by HypoSAT location method and double difference location method. It is concluded that the epicenter position of the main earthquake is 30.73°N and 104.48°E. From February 4 to June 26, 2020, a total of 61 aftershock events were relocated, with magnitude 0≤ML≤3.0 and depth ranging from near surface to 15km. The 61 aftershocks spread about 5km in the NW-SE direction and have conjugate distribution in NW and NE directions, which may be related to the small thrust fault developed on the east branch of Longquan Shan Fault. Aftershocks have a good linear distribution in NE direction, which is closer to the east branch of the north segment of Longquan Shan fault zone, and the distribution direction is also consistent with the fault strike. On the seismic reflection profile, the aftershock projection is densely distributed along the east branch fault. The occurrence of the east branch fault is consistent with the focal mechanism nodal plane I, which is a low angle thrust fault dipping to NW. The InSAR coseismic deformation field near the epicenter is extracted by using the Sentinel data of orbit 55 and orbit 62 collected from ESA, including 8 single view complex images of orbit 55 and orbit 62, respectively. The surface deformation caused by this earthquake is in the middle of two thrust faults, and the maximum coseismic deformation can reach 4cm. The deformation caused by the earthquake is uplifting in the northwest and depressing in the southeast of the epicenter. The largest depression is located between the epicenter and the east branch fault. The thrust activity of the east branch fault is more in line with the above surface deformation characteristics. In this study, the seismotectonics of the 2020 Qingbaijiang MS5.1 earthquake is analyzed in detail using multi-disciplinary and multi-constraint method. The east branch fault in the north segment of the fault zone is determined as the seismogenic fault, and the possible seismic dynamic background is discussed. This result provides a scientific basis for fault activity analysis and seismic risk assessment in Longquan Shan area and has a great significance for further exploring the expansion and growth of Longmen Shan in the southeast margin of Tibetan plateau toward Sichuan Basin.

Key words: Qingbaijiang MS5.1 earthquake, seismic reflection profile, seismic relocation, InSAR coseismic deformation field, Longquanshan fault zone


2020年2月3日, 四川省成都市青白江区发生 MS5.1 地震, 震中位于川西盆地的龙泉山断裂带北段。龙泉山断裂带北段存在东、 西2支断层, 2条断层与震中的距离相近。目前, 此次地震的发震断层、 地震成因与动力来源尚不清楚。文中尝试采用多元约束方法, 将地球物理学、 地震学、 大地测量学理论和构造地质学与断层相关褶皱理论相结合, 对青白江 MS5.1 地震进行了综合研究。地震反射剖面揭示了龙泉山背斜北段的基本构造特征, 为发育在4~6km深度的中下三叠统膏盐滑脱层之上的逆冲断层和反冲断层的组合, 且具有突破式断层传播褶皱特征; 研究中采用CAP波形反演法得到了此次地震的震源矩心深度和震源机制解, 其中震源矩心深度为5km, 表明地震与浅层断层活动有关; 震源机制解的节面Ⅰ为18°/32°/100°, 节面Ⅱ为186°/59°/84°; 通过Hyposat定位法和双差定位法对青白江地震序列进行重定位, 得到主震的震中位置为(30.73°N, 104.48°E), 定位的61次余震主要集中分布于龙泉山断裂带北段东支附近, 且具有较好的关联性, 东支断层的产状与震源机制解节面Ⅰ一致, 为倾向NW的低角度逆断层。研究提取了震中附近的InSAR同震形变场, 同震形变量最大可达4cm; 地震造成的形变在震中西北部为隆起, 东南部为凹陷, 且最大凹陷部位位于震中与龙泉山东支断裂之间, 符合东支断裂逆冲的活动特征。文中通过多学科交叉的多元约束, 对2020年青白江 MS5.1 地震的发震构造进行了详细分析, 厘定了发震断层并探讨了可能的地震动力学背景, 可为龙泉山地区的断层活动性分析和地震风险评估提供一定的科学依据。

关键词: 青白江MS5.1地震, 地震反射剖面, 地震重定位, InSAR同震形变, 龙泉山断裂带

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