2021年漾濞<i>M</i><sub>S</sub> 6.4地震序列震源特征及发震构造研究

周民婷; 何骁慧; 刘智良; 王伟涛

doi:10.12090/j.issn.1006-6616.2025183

2021年漾濞M_S 6.4地震序列震源特征及发震构造研究

doi: 10.12090/j.issn.1006-6616.2025183

周民婷^{1, 2,},
何骁慧^{1, 2, 3, ,},
刘智良^{1, 2,},
王伟涛^4,

1.
中山大学地球科学与工程学院，广东珠海 519082
2.
广东省地球动力作用与地质灾害重点实验室，广东珠海 519082
3.
南方海洋科学与工程广东省实验室（珠海），广东珠海 519082
4.
中国地震局地球物理研究所，北京 100081

基金项目: 国家自然科学基金项目（42494913，42474070）

详细信息

作者简介:
周民婷（2004—），女，在读硕士，地球物理专业。Email：zhoumt7@mail2.sysu.edu.cn

通讯作者:
何骁慧（1991—），女，博士，副教授，主要从事地震学的研究。Email：hexiaoh5@mail.sysu.edu.cn

中图分类号: P315；P546
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出版历程
- 收稿日期: 2025-12-18
- 修回日期: 2026-05-12
- 录用日期: 2026-05-27
- 预出版日期: 2026-06-10
- 刊出日期: 2026-06-28

Study on the source characteristics and seismogenic structure of the 2021 Yangbi M_S6.4 earthquake sequence

ZHOU Minting^{1, 2
,},
HE Xiaohui^{1, 2, 3
, ,},
LIU Zhiliang^{1, 2
,},
WANG Weitao^4
,

1.
School of Earth Sciences and Engineering, Sun Yat-sen University, Zhuhai 519082, Guangdong, China
2.
Guangdong Provincial Key Laboratory of Geodynamics and Geohazards, Zhuhai 519082, Guangdong, China
3.
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, Guangdong, China
4.
Institute of Geophysics, China Earthquake Administration, Beijing 100081, China

Funds: This research was financially supported by the National Nature Science Foundation of China (Grant Nos. 42494913 and 42474070).

摘要

摘要: 为明确2021年云南漾濞M_S 6.4地震序列的发震构造与破裂特征，解决已有研究在孕震断层认识上的争议，文章采用相对质心定位法和震源时频特征法，选取已知机制解的小震作为参考事件，对序列中10次M_S ≥ 4.0地震开展了破裂方向性参数测定；同时基于近震台站记录，估算了M_S  ≥ 3.0地震能量的辐射效率。结果表明：漾濞地震序列的破裂方向呈现显著的空间分段特征，北西段5次地震的发震断层均为北西向，南东段4次地震兼有北西向和北东向。M_S  5.6最大前震与M_S  5.2最大余震的破裂方向均指向北东向，且发生在共轭断层上；而M_S 6.4主震破裂方向为北西向，与北西段主断层一致，表明南东段共轭断层活动是序列的重要组成部分。M_S 4.4前震具有频率依赖的双侧破裂特征，其中相对质心法测得结果为北西向，时频法测得结果为南东向。辐射效率同样存在分段差异，结合区域地质背景，推测该差异由北西段与南东段的断层摩擦性质不同所致。研究结果深化了对该区构造背景和地震孕育过程的认识，可为未来地震危险性评估提供地震学参考。
- 漾濞M_S 6.4地震 /
- 地震序列 /
- 震源机制 /
- 发震构造 /
- 破裂方向性
Abstract: Objective On 21 May 2021, an M_S6.4 earthquake struck Yangbi County, Dali Prefecture, Yunnan Province — the largest event near the Weishan Basin segment of the Weixi–Qiaohou fault since 1976. The mainshock produced no surface rupture and did not occur on any known active fault. Despite numerous previous studies, the precise seismogenic structure and causative faults of this typical foreshock–mainshock–aftershock sequence (including seven M_S  ≥ 4.0 foreshocks and 22 M_S ≥ 4.0 aftershocks) remain controversial; some results are poorly constrained or even mutually contradictory. Furthermore, the occurrence of moderate-to-strong earthquakes surrounding the source area has increased significantly in recent years. This study thus aims to elucidate the rupture behaviour and seismogenic environment of the entire earthquake sequence. Methods Using pre-existing focal mechanism solutions of minor earthquakes as reference events, we adopted the relative centroid relocation method and time–frequency source characterisation method to calculate rupture directivity parameters for ten M_S ≥ 4.0 events. In addition, we calculated the radiation efficiency for all M_S ≥ 3.0 earthquakes based on waveform recording from local seismic station. Results Our results demonstrate distinct along-strike segmentation of rupture directivity across the Yangbi sequence. On the northwestern segment of the sequence, five earthquakes feature NW-striking fault planes. On the southeastern segment, four earthquakes exhibit faults either NW or NE. The largest foreshock (M_S 5.6) and the largest aftershock (M_S 5.2) both rupture toward the NE, indicating that they did not occur on the same fault as the M_S 6.4 mainshock. Combined with previous relocation and geodetic results, we interpret that these two events occurred on conjugate faults. The M_S 6.4 mainshock ruptured toward the NW, consistent with the dominant rupture azimuth of the NW segment, suggesting that the mainshock primarily ruptured the NW-trending master fault, whereas conjugate faulting in the SE segment constitutes an important component of the entire sequence. For the M_S 4.4 foreshock, the relative centroid method yields a rupture direction toward the NW, while the time–frequency source method gives a direction toward the SE. This event is therefore interpreted as a frequency-dependent bilateral rupture. We further calculated and corrected the radiation efficiency values for all M_S≥ 3.0 events. The efficiency results show a similar along-strike segmentation: the radiation efficiency differs systematically between the NW and SE segments. Integrating rupture directivity patterns, radiation efficiency measurements and regional geological constraints, we infer that the segmentation in rupture directivity is primarily caused by differences in fault frictional properties between the NW and SE segments. Conclusions The Yangbi earthquake sequence exhibits distinct segmentation in rupture directivity, with the NW segment dominated by NW-striking master fault rupture and the SE segment characterized by conjugate faulting. The M_S 4.4 foreshock corresponds to a frequency-dependent bilateral rupture event. The segmentation in radiation efficiency further supports the interpretation of different fault frictional regimes along the fault strike. [Significance] These findings deliver new constraints on the source characteristics and seismogenic structure of the Yangbi earthquake sequence. They improve our knowledge of the regional tectonic setting and earthquake nucleation cycle, and offer valuable seismological evidence for future seismic hazard assessment across the study area.
- Yangbi M_S 6.4 earthquake /
- earthquake sequence /
- source mechanism /
- seismogenic structure /
- rupture directionality
注释:
Author’s Contributions:
HE Xiaohui and ZHOU Minting conceived the study, performed data analysis, designed the research methodology, and drafted the manuscript; ZHOU Minting and LIU Zhiliang participated in data analysis, practical application of technical approaches, and figure generation; HE Xiaohui and WANG Weitao were involved in data analysis, refinement of the research methodology, and manuscript revision. All authors have read and approved the submission and publication of the manuscript.
Conflict of Interests:
All authors declare no conflict of interests.

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图 1 研究区周缘主要断裂带及地震分布图

CXB—川西北次级块体；DZB—滇中次级块体；BSB—保山次级块体；ICB—印支块体；地震数据引自地震科学国际数据中心(地震科学国际数据中心，2021)，断裂数据引自中国活动构造图（邓起东，2007）a—青藏高原及邻区大地构造位置；b—川滇块体主要断裂带及历史地震分布图（1900年以来）；c—2021年5月21日漾濞M_S 6.4地震序列中M_S ≥3.0事件空间分布图（2021年5月18日—2021年5月28日）

Figure 1. Distribution of major fault zones and earthquakes in the study area and its periphery

(a) Tectonic setting of the Tibetan Plateau and adjacent regions; (b) Distribution of major fault zones and historical earthquakes since 1900 within the Sichuan–Yunnan block; (c) Spatial distribution of M_S≥ 3.0 events (18–28 May, 2021) within the 21 May, 2021 Yangbi M_S 6.4 earthquake sequence CXB—northwestern Sichuan sub-block; DZB—central Yunnan sub-block; BSB—Baoshan sub-block; ICB—Indochina block; earthquake data from the National Earthquake Science Data Center(International Earthquake Science Data Center, 2021), and fault data from Active Tectonic Map of China (Deng, 2007)

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图 2 漾濞地震区域台站分布图

蓝色三角形为国家地震科学数据中心长周期宽频带数字记录台站；红色三角形为中国地震局地球物理研究所主动源团队短周期数字记录台阵；黄色五角星为M_S 6.4主震；橙红色三角形分别为YUL台站和TUS台站

Figure 2. Distribution of seismic stations around the Yangbi earthquake region

Blue triangles represent long-period broadband digital recording stations from the National Center for Seismic Data Backup of the China National Seismic Network; Red triangles represent the short-period digital recording array of the Active Source Team, Institute of Geophysics, China Earthquake Administration; The yellow five-pointed star marks the M_S 6.4 mainshock; Orange-red triangles indicate the YUL station and the TUS station, respectively.

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图 3 重定位后的主事件与参考事件的空间分布图及震源机制解对比图

Figure 3. Spatial distribution and comparison of focal mechanism solutions for the relocated main event and reference events

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图 4 漾濞M_S 6.4主震破裂方向性反演结果

stk1—漾濞M_S 6.4主震节面1走向；stk2—漾濞M_S 6.4主震节面2走向；err—拟合误差；图a—d中的余弦曲线分别为震源机制解的2个可能节面的理论走向拟合曲线；灰色圆点为不同展台观测波形与理论波形之间的时移差a—以2021-05-18 M_S 3.2作为参考事件所得的破裂方向性拟合结果；b—以2021-05-18 M_S 3.0作为参考事件所得的破裂方向性拟合结果；c—以2021-05-18 M_S 4.2作为参考事件所得的破裂方向性拟合结果；d—以2021-05-18 M_S 3.1作为参考事件所得的破裂方向性拟合结果；e—漾濞M_S 6.4主震破裂方向示意图；f—漾濞M_S 6.4主震破裂尺度

Figure 4. Rupture directivity inversion results of the Yangbi M_S 6.4 mainshock

(a) Rupture directivity fitting results using event 2021-05-18 M_S 3.2 as the reference; (b) Rupture directivity fitting results using event 2021-05-18 M_S 3.0 as the reference; (c) Rupture directivity fitting results using event 2021-05-18 M_S 4.2 as the reference; (d) Rupture directivity fitting results using event 2021-05-18 M_S 3.1 as the reference; (e) Schematic diagram of the rupture directivity of the Yangbi M_S 6.4 mainshock; (f) Rupture scale of the Yangbi M_S 6.4 mainshockstk1—strike of nodal plane 1 of the Yangbi M_S 6.4 mainshock; stk2—strike of nodal plane 2 of the Yangbi M_S 6.4 mainshock; err—fitting error; In panels a to d, the cosine curves are the theoretical strike fitting curves for the two possible nodal planes of the focal mechanism solution, respectively; The gray dots represent the time shift differences between the observed waveforms and the synthetic waveforms at different stations.

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图 5 漾濞2021-05-21 M_S 5.6前震破裂方向性反演结果

stk1—2021-05-21 M_S 5.6前震节面1走向；stk2—2021-05-21 M_S 5.6前震节面2走向；err—拟合误差；图a—d中的余弦曲线分别为震源机制解的2个可能节面的理论走向拟合曲线；灰色圆点为不同展台观测波形与理论波形之间的时移差a—以2021-05-18 M_S 3.2作为参考事件所得的破裂方向性拟合结果；b—以2021-05-18 M_S 3.0作为参考事件所得的破裂方向性拟合结果；c—以2021-05-18 M_S 3.1作为参考事件所得的破裂方向性拟合结果；d—以2021-05-18 M_S 3.6作为参考事件所得的破裂方向性拟合结果；e—漾濞2021-05-21 M_S 5.6前震破裂方向示意；f—漾濞2021-05-21 M_S 5.6前震破裂尺度

Figure 5. Rupture directivity inversion results of the Yangbi 2021-05-21M_S 5.6 foreshock

(a) Rupture directivity fitting results using event 2021-05-18 M_S 3.2 as the reference; (b) Rupture directivity fitting results using event 2021-05-18 M_S 3.0 as the reference; (c) Rupture directivity fitting results using event 2021-05-18 M_S 3.1 as the reference; (d) Rupture directivity fitting results using event 2021-05-18 M_S 3.6 as the reference; (e) Schematic diagram of rupture direction for the Yangbi 2021-05-21M_S 5.6 foreshock; (f) Rupture scale of the Yangbi 2021-05-21M_S 5.6 foreshockstk1—strike of nodal plane 1 of the 2021-05-21 M_S 5.6 foreshock; stk2—strike of nodal plane 2 of the 2021-05-21 M_S 5.6 foreshock; err—fitting error; In panels a to d, the cosine curves are the theoretical strike fitting curves for the two possible nodal planes of the focal mechanism solution, respectively; the gray dots represent the time shift differences between the observed waveforms and the synthetic waveforms at different stations.

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图 6 漾濞2021-05-19 M_S 4.4前震破裂方向性反演结果

stk1—2021-05-19 M_S 4.4前震节面1走向；stk2—2021-05-19 M_S 4.4前震节面2走向；err—拟合误差；图a—d中的余弦曲线分别为震源机制解的2个可能节面的理论走向拟合曲线；灰色圆点为不同台站观测波形与理论波形之间的时移差a—以2021-05-18 M_S 3.2作为参考事件所得的破裂方向性拟合结果；b—以2021-05-22 M_S 2.9作为参考事件所得的破裂方向性拟合结果；c—以2021-05-21 M_S 3.2作为参考事件所得的破裂方向性拟合结果；d—以2021-05-24 M_S 3.0作为参考事件所得的破裂方向性拟合结果；e—漾濞2021-05-19 M_S 4.4前震破裂方向示意；f—漾濞2021-05-19 M_S 4.4前震破裂尺度

Figure 6. Rupture directivity inversion results of the Yangbi 2021-05-19 M_S 4.4 foreshock

(a) Rupture directivity fitting results using event 2021-05-18 M_S 3.2 as the reference; (b) Rupture directivity fitting results using event 2021-05-22 M_S 2.9 as the reference; (c) Rupture directivity fitting results using event 2021-05-21 M_S 3.2 as the reference; (d) Rupture directivity fitting results using event 2021-05-24 M_S 3.0 as the reference; (e) Schematic diagram of rupture direction for the Yangbi 2021-05-19 M_S 4.4 foreshock; (f) Rupture scale of the Yangbi 2021-05-19 M_S 4.4 foreshockstk1—strike of nodal plane 1 of the 2021-05-19 M_S 4.4 foreshock; stk2—strike of nodal plane 2 of the 2021-05-19 M_S 4.4 foreshock; err—fitting error; In panels a to d, the cosine curves are the theoretical strike fitting curves for the two possible nodal planes of the focal mechanism solution, respectively; the gray dots represent the time shift differences between the observed waveforms and the synthetic waveforms at different stations.

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图 7 漾濞2021-05-21 M_S 5.2余震破裂方向性反演结果

stk1—2021-05-21 M_S 5.2余震节面1走向；stk2—2021-05-21 M_S 5.2余震节面2走向；err—拟合误差；图a、b、c、g、h、i中的余弦曲线分别为震源机制解的2个可能节面的理论走向拟合曲线；灰色圆点代表各个台站的方位角所对应的最佳震源持续时间，震源持续时间最小的点所对应的方位角即为地震破裂方向a—以2021-05-18 M_S 3.2作为参考事件所得的震源持续时间随方位角的变化；b—以2021-05-19 M_S 2.9作为参考事件所得的震源持续时间随方位角的变化；c—以2021-05-21 M_S 4.0作为参考事件所得的震源持续时间随方位角的变化；d—以2021-05-18 M_S 3.2作为参考事件所得的波形拟合结果；e—以2021-05-18 M_S 2.9作为参考事件所得的波形拟合结果；f—以2021-05-21 M_S 4.0作为参考事件所得的波形拟合结果；g—以2021-05-21 M_S 3.2作为参考事件所得的震源持续时间随方位角的变化；h—以2021-05-22 M_S 2.9作为参考事件所得的震源持续时间随方位角的变化；i—以2021-05-27 M_S 3.6作为参考事件所得的震源持续时间随方位角的变化；j—以2021-05-21 M_S 3.2作为参考事件所得的波形拟合结果；k—以2021-05-22 M_S 2.9作为参考事件所得的波形拟合结果；l—以2021-05-27 M_S3.6作为参考事件所得的波形拟合结果；m—节面1与节面2拟合残差统计直方图；n—破裂长度统计；o—2021-05-21 M_S 5.2余震破裂方向示意

Figure 7. Inversion results of the rupture directivity of the Yangbi M_S5.2 aftershock

(a) Variation of source duration with azimuth obtained using event 2021-05-18 M_S 3.2 as the reference; (b) Variation of source duration with azimuth obtained using event 2021-05-19 M_S 2.9 as the reference; (c) Variation of source duration with azimuth obtained using event 2021-05-21 M_S 4.0 as the reference; (d) Waveform fitting obtained using event 2021-05-18 M_S 3.2 as the reference; (e) Waveform fitting obtained using event 2021-05-18 M_S 2.9 as the reference; (f) Waveform fitting obtained using event 2021-05-21 M_S 4.0 as the reference; (g) Variation of source duration with azimuth obtained using event 2021-05-21 M_S 3.2 as the reference; (h) Variation of source duration with azimuth obtained using event 2021-05-22 M_S 2.9 as the reference; (i) Variation of source duration with azimuth obtained using event 2021-05-27 M_S 3.6 as the reference; (k) Waveform fitting obtained using event 2021-05-22 M_S 2.9 as the reference; (l) Waveform fitting obtained using event 2021-05-27 M_S 3.6 as the reference; (m) Histogram of residuals between nodal plane 1 and nodal plane 2; (n) Statistics of rupture lengths; (o) Schematic diagram of rupture direction of the 2021-05-19 M_S 4.4 foreshock stk1—strike of nodal plane 1 of the 2021-05-21 M_S 5.2 aftershock; stk2—strike of nodal plane 2 of the 2021-05-21 M_S 5.2 aftershock; err—fitting error; In panels a, b, c, g, h, and i, the cosine curves represent the fitting results corresponding to the two nodal planes of the focal mechanism solution, respectively; and the gray circles represent the optimal source duration at the azimuths of individual stations, the azimuth corresponding to the minimum source duration indicates the earthquake rupture direction.

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图 8 漾濞2021-05-19 M_S 4.4前震破裂方向性反演结果

stk1—2021-05-19 M_S 4.4前震节面1走向；stk2—2021-05-19 M_S 4.4前震节面2走向；err—拟合误差；图a、b、e、f中的余弦曲线分别代表震源机制解的两个节面对应的拟合结果；灰色圆点代表各个台站的方位角所对应的最佳震源持续时间，震源持续时间最小的点所对应的方位角即为地震破裂方向a—以2021-05-18 M_S 2.8作为参考事件所得的震源持续时间随方位角的变化；b—以2021-05-18 M_S 3.2作为参考事件所得的震源持续时间随方位角的变化；c—以2021-05-18 M_S 2.8作为参考事件所得的波形拟合结果；d—以2021-05-18 M_S 3.2作为参考事件所得的波形拟合结果；e—以2021-05-18 M_S 2.5作为参考事件所得的震源持续时间随方位角的变化；f—以2021-05-19 M_S 3.2作为参考事件所得的震源持续时间随方位角的变化；g—以2021-05-18 M_S 2.5作为参考事件所得的波形拟合结果；h—以2021-05-19 M_S 3.2作为参考事件所得的波形拟合结果；i—节面1与节面2拟合残差统计直方图；j—破裂长度统计；k—2021-05-19 M_S 4.4前震破裂方向示意

Figure 8. Inversion results of the rupture directivity of the Yangbi M_S 4.4 foreshock

(a) Variation of source duration with azimuth obtained using event 2021-05-18 M_S 2.8 as the reference; (b) Variation of source duration with azimuth obtained using event 2021-05-18 M_S 3.2 as the reference; (c) Waveform fitting obtained using event 2021-05-18 M_S 2.8 as the reference; (d) Waveform fitting obtained using event 2021-05-18 M_S 3.2 as the reference; (e) Variation of source duration with azimuth obtained using event 2021-05-18 M_S 2.5 as the reference; (f) Variation of source duration with azimuth obtained using event 2021-05-19 M_S 3.2 as the reference; (g) Waveform fitting obtained using event 2021-05-18 M_S 2.5 as the reference; (h) Waveform fitting obtained using event 2021-05-19 M_S 3.2 as the reference; (i) Histogram of residuals between nodal plane 1 and nodal plane 2; (j) Statistics of rupture lengths; (k) Schematic diagram of rupture direction of the 2021-05-19 M_S 4.4 foreshockstk1—strike of nodal plane 1 of the 2021-05-19 M_S 4.4 foreshock; stk2—strike of nodal plane 2 of the 2021-05-19 M_S 4.4 foreshock; err—fitting error; In panels a, b, e, and f, the cosine curves represent the fitting results corresponding to the two nodal planes of the focal mechanism solution, respectively; and the gray circles represent the optimal source duration at the azimuths of individual stations, the azimuth corresponding to the minimum source duration indicates the earthquake rupture direction.

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图 9 漾濞M_S 6.4地震破裂方向性示意图

蓝色震源球代表具有双侧破裂的特殊地震事件，红色震源球代表其余求得准确破裂方向性参数的地震事件，均已标记出文中研究所得断层破裂方向；红色虚线代表根据文中破裂方向性测定结果结合已有研究成果推测的发震断层；灰色圆点代表地震序列重定位分布（Tian et al.，2023）；蓝色虚线代表破裂分段示意线，用于直观划分北西与南东方向的破裂分段特征；红色五角星代表漾濞地震序列M_S >5.2的地震；黑色实线代表震源区断层分布（引自李传友等，2021；龙锋等，2021）

Figure 9. Schematic diagram of the rupture directivity of the Yangbi earthquake

Blue beach balls represent special seismic events with bilateral rupture; red beach balls represent the remaining events for which accurate rupture directivity parameters were obtained; the fault rupture direction determined in this study is marked for all of them. The red dashed line indicates the inferred seismogenic fault based on the rupture directivity results from this study combined with previous research; gray dots show the relocated distribution of the earthquake sequence (Tian et al., 2023); the blue dashed line is a schematic line for rupture segmentation, used to visually delineate the segmentation characteristics in the NW and SE directions; red five-pointed stars represent earthquakes with M_S  > 5.2 in the Yangbi sequence; black solid lines show the fault distribution in the source area (from the regional seismotectonic map of the Yangbi swarm – overlay mapping, Li et al., 2021; Long et al., 2021).

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图 10 2个台站记录的特殊事件与参考事件的波形及振幅谱对比

a—TUS台站记录的特殊事件及参考事件的波形对比；b—TUS台站记录的特殊事件与参考事件的P波振幅谱对比；c—YUL台站所记录的特殊事件与参考事件的波形对比；d—YUL台站记录的特殊事件与参考事件的P波振幅谱对比

Figure 10. Comparison of waveforms and amplitude spectra of the special event and reference earthquake recorded at two stations

(a) Waveforms of the special event and the reference earthquake recorded at station TUS; (b) Comparison of P-wave amplitude spectra of the special event and the reference earthquake at station TUS; (c) Waveforms of the special event and the reference earthquake recorded at station YUL; (d) Comparison of P-wave amplitude spectra of the special event and the reference earthquake at station YUL

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图 11 能量辐射效率图

黄色五角星为地震序列特殊事件2021-05-19 M_S 4.4；红色虚线为破裂分段示意线，用于直观划分北西与南东方向的破裂分段特征a—观测地震波形能量辐射效率；b—理论地震波形能量辐射效率；c—校正后地震波形能量辐射效率

Figure 11. Energy radiation efficiency diagram

(a) Observed seismic waveform radiated energy efficiency; (b) Synthetic seismic waveform radiated energy efficiency; (c) Corrected seismic waveform radiated energy efficiencyThe yellow five-pointed star represents the special event 2021-05-19 M_S 4.4 in the earthquake sequence; the red dashed line is a schematic line for rupture segmentation, used to visually delineate the rupture segmentation characteristics in the northwest and southeast directions

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表 1 相对质心定位测定破裂方向性结果（震源机制解引自王月等，2021）

Table 1. Results of rupture directivity determined by relative centroid location (Focal mechanism solution from Wang et al., 2021)

地震名	节面1 （走向/倾角/滑动角）	节面2 （走向/倾角/滑动角）	破裂方向	破裂长度	参考事件数	支持同一破裂方向的参考事件数
2021-05-19 M_S 4.4前震	229°/90°/−14°	319°/76°/−180°	NW	3.0 km	10	10
2021-05-21 M_S 5.6前震	214°/77°/−20°	309°/70°/−167°	NE	3.0 km	15	15
2021-05-21 M_S 6.4主震	44°/78°/16°	138°/74°/168°	SE	12.8 km	19	19

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表 2 震源时频特征法测定破裂方向性统计表（震源机制解引自王月等，2021）

Table 2. Statistical table of rupture directivity determined by the source time-frequency characteristic method

地震名	节面1（走向/倾角/滑动角）	节面2（走向/倾角/滑动角）	破裂方向	破裂长度	参考事件数	支持同一破裂方向参考事件数
2021-05-18 M_S 4.2前震	41°/75°/11°	308°/79°/164°	NW	1.0 km	24	17
2021-05-19 M_S 4.4前震	229°/90°/−14°	319°/76°/−180°	SE	2.2 km	13	12
2021-05-21 M_S 4.2前震	23°/57°/−52°	149°/48°/−133°	SW	1.5 km	27	20
2021-05-21 M_S 4.5前震	218°/83°/8°	127°/82°/172°	NW	1.0 km	18	13
2021-05-21 M_S 4.1余震	203°/45°/−44°	328°/60°/−126°	NW	1.8 km	35	31
2021-05-21 M_S 4.0余震	210°/73°/10°	117°/80°/162°	NW	1.5 km	24	18
2021-05-21 M_S 5.2余震	40°/71°/−46°	148°/47°/−153°	NE	1.8 km	34	30
2021-05-22 M_S 4.0余震	34°/80°/−17°	127°/73°/−170°	NW	1.5 km	35	30

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