JOINT INVERSION OF THE RUPTURE PROCESS OF 2018 ML5.7 XINGWEN EARTHQUAKE BASED ON SEISMIC AND INSAR OBSERVATIONS

doi:10.3969/j.issn.0253-4967.2024.02.009

SEISMOLOGY AND GEOLOGY ›› 2024, Vol. 46 ›› Issue (2): 397-413.DOI: 10.3969/j.issn.0253-4967.2024.02.009

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JOINT INVERSION OF THE RUPTURE PROCESS OF 2018 M_L5.7 XINGWEN EARTHQUAKE BASED ON SEISMIC AND INSAR OBSERVATIONS

MIAO Si-yu¹⁾(), ZHANG Hai-jiang¹⁾^,^*(), GU Ning²⁾^,^*(), LI Jun-lun¹⁾, TAN Yu-yang³⁾, HUA Si-bo⁴⁾, ZHANG Yong⁴⁾

¹⁾ School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
²⁾ Department of Earth and Space Sciences, Southern University of Sciences and Technology, Shenzhen 518055, China
³⁾ Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Lab of Submarine Geosciences and Prospecting Techniques, MOE and College of Marine Geosciences, Ocean University of China, Qingdao 266100, China
⁴⁾ School of Earth and Space Sciences, Peking University, Beijing 100871, China

Received:2022-12-04 Revised:2023-08-24 Online:2024-04-20 Published:2024-05-29

基于地震和InSAR联合反演2018年M_L5.7兴文地震破裂过程

缪思钰¹⁾(), 张海江¹⁾^,^*(), 古宁²⁾^,^*(), 李俊伦¹⁾, 谭玉阳³⁾, 华思博⁴⁾, 张勇⁴⁾

¹⁾ 中国科学技术大学, 地球和空间科学学院, 合肥 230026
²⁾ 南方科技大学, 地球与空间科学系, 深圳 518055
³⁾ 中国海洋大学海洋地球科学学院, 青岛深海圈层与地球系统教育部前沿科学中心,海底科学与探测技术教育部重点实验室, 青岛 266100
⁴⁾ 北京大学, 地球与空间科学学院, 北京 100871

通讯作者: *张海江, 男, 1973年生, 博士, 教授, 主要从事地震成像和微地震研究, E-mail: zhang11@ustc.edu.cn。古宁, 男, 1993年生, 博士后, 主要从事地震干涉成像研究, E-mail: guning@sustech.edu.cn。
作者简介:
缪思钰, 女, 1994年生, 2022年于中国科学技术大学获地球物理学博士学位, 主要研究方向为微地震定位和地震破裂过程研究, E-mail: miaosy@mail.ustc.edu.cn。
基金资助:
国家重点研发计划项目(2022YFF0800701)

Abstract

Abstract:

The M_L5.7 Xingwen earthquake on December 16, 2018 is very likely induced by shale gas hydraulic fracturing, which caused not only massive landslides and rock collapse, but also some casualties in the surrounding area, with the direct economic loss of about 50 million CNY. It is of great significance to determine the source rupturing process of such an induced earthquake with large magnitude.

Finite fault inversion is one of the commonly adopted methods to determine coseismic slip displacement distribution. For finite fault inversion, various data have different sensitivities to various aspects of the rupture process. The seismic data can provide the historical information about the earthquake rupture process because it contains the Doppler effect of the space-time rupture behavior on the fault. In comparison, the near-field geodetic data(such as InSAR and GPS)can constrain the fault parameters and the static slip distribution well because they contain the surface motion information. Therefore, the reliability of the inversion for the complex seismic rupture process can greatly be improved by combined use of seismicdata and InSAR data.

In this study, strong-motion seismic data recorded at 8 near-field stations are chosen and filtered by a band-pass of 0.15-0.60Hz. The same InSAR data used in Wang et al.(2022)is adopted in this joint study. For inversion, a sufficiently large potential fault plane of 15km long and 10km wide is chosen and divided into 15×10 subfaults. Finally, the rupture process is obtained by joint inversion of strong-motion seismic data and InSAR data. The results show that the earthquake is characterzied by a typical unilateral rupture with the rupturing direction nearly towards the north. The duration of the rupture process was 6s, and the energy release was mainly concentrated in the first 5s. The rupture process is segmented and can be divided into two stages. The first stage is distributed from 1-3s and is located in the range of 0~5km from the source; and the 2nd stage is distributed from 3-5s and is located between 6 and 8km from the source. The coseismic slip is mainly concentrated in areas shallower than 5km, with a peak slip of approximately 0.27m. This can be used to explain why the Xingwen earthquake with a magnitude of M_L5.7 caused relatively serious damages.

Combined with the distribution of foreshocks and aftershocks, it can be seen that the foreshocks were mainly concentrated to the eastern edge of the major coseismicslip zone, which are close to some hydraulic fracturing wells. This suggests that these foreshocks occuring at the edge of the main rupture zone has a certain correlation with fluids, and the presence of fluids further leads to the fault weakening of the mainshock due to the increase of pore pressure and the decrease of effective compressive stress, which plays a triggering role in the occurrence of the Xingwen earthquake. The aftershocks are mainly distributed around the main slip zone, which are caused by after slips after the mainshock. The results from seismic inversion, InSAR inversion and joint inversion of the two data types reveal that the Xingwen earthquake is a northward unilateral rupture. The rupture propagation direction and coseismic slip distribution may be related to the physical property changes along the fault plane.

Compared with the two single inversion results, the joint inversion overcomes the influence of uneven distribution of seismic stations, improves the resolution of slip distribution, and produces results that are more consistent with the real physical process. The slip model obtained by joint inversion in this study can be helpful for further understanding the mechanisms of induced earthquake, the correlation between induced earthquake and geological structure, earthquake disaster assessment and post-earthquake disaster prevention and hazard mitigation.

Key words: Xingwen earthquake, earthquake rupture process, induced earthquake, finite fault inversion, joint inversion of seismic and InSAR data

摘要：

2018年12月16日发生的M_L5.7兴文地震很可能是由页岩气水力压裂所诱发, 确定此类震级较大的诱发地震的震源破裂过程具有重要意义。文中利用近震数据和InSAR数据联合反演, 获得了兴文地震的破裂过程。与单独使用地震数据或InSAR数据进行反演相比, 联合反演得到的地震破裂过程可同时拟合2种类型数据, 因此具有更高的时空分辨率。联合反演结果显示该地震为典型的单侧破裂, 破裂方向近N向。破裂过程的持续时间为6s, 能量释放主要集中在前5s, 呈分段式破裂。主震破裂过程分为2个阶段: 沿着断裂的走向, 紧挨着震中的0~5km范围内为破裂的第1阶段(1~3s); 距震中6~8km处为破裂的第2阶段(3~5s)。同震滑移主要集中在5km以浅的区域, 峰值滑移约为0.27m, 这可以解释为何M_L5.7兴文地震造成了较为严重的破坏。结合前震和余震分布可以看出, 前震主要集中在滑移区的东部, 说明该区域在主震发生之前就已发生破裂, 意味着该区域可能存在注入的流体。余震主要分布在滑移区周围, 是由主震破裂后的余滑引起的。对比单独反演结果, 联合反演克服了台站分布不均匀的影响, 提高了破裂分布的分辨率, 所得结果更加符合真实物理过程。文中联合反演得到的破裂模型为进一步研究诱发地震机理、地震灾害评估和震后防灾减灾奠定了基础。

关键词: 兴文地震, 地震破裂过程, 诱发地震, 有限断层反演, InSAR联合反演

MIAO Si-yu, ZHANG Hai-jiang, GU Ning, LI Jun-lun, TAN Yu-yang, HUA Si-bo, ZHANG Yong. JOINT INVERSION OF THE RUPTURE PROCESS OF 2018 M_L5.7 XINGWEN EARTHQUAKE BASED ON SEISMIC AND INSAR OBSERVATIONS[J]. SEISMOLOGY AND GEOLOGY, 2024, 46(2): 397-413.

缪思钰, 张海江, 古宁, 李俊伦, 谭玉阳, 华思博, 张勇. 基于地震和InSAR联合反演2018年M_L5.7兴文地震破裂过程[J]. 地震地质, 2024, 46(2): 397-413.

Figures/Tables 10

Fig. 1 The distribution of local seismic stations and earthquakes used in the Xingwen earthquake rupture process inversion.

Fig. 2 The restored waveforms for the clipped waveforms recorded at stations XWJ and CJW.

Fig. 3 One-dimensional velocity models used in the calculation of Green’s functions of the Xingwen earthquake for the strong-motion stations.

Fig. 4 The rupture process for the 2018 Xingwen earthquake inverted using only strong motion data.

Fig. 5 The rupture process for the 2018 Xingwen earthquake inverted using only InSAR data.

Fig. 6 Observed and synthetic interferograms by InSAR data inversion only.

Fig. 7 Trade-off analysis between RMS residuals of strong-motion and InSAR data.

Fig. 8 The rupture process inversion results for the 2018 Xingwen earthquake jointly inverted by strong motion data and InSAR data.

Fig. 9 Spatial-temporal distribution of slips on the fault plane of Xingwen earthquake.

Fig. 10 Spatial distribution of coseismicslips, foreshocks(within 15 days)and aftershocks(within 15 days) on the fault plane of Xingwen earthquake.

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