Relocation and source characteristics of the 2019 Changning MS6.0 earthquake sequence
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摘要: 采用双差定位方法对2019年1月1日至2019年10月20日期间四川区域台网记录到的地震进行重定位，得到7 030个重定位事件，并获得了四川长宁MS6.0地震序列较准确的空间分布，并据此计算了震后长宁震源区的平均b值，分析了地震序列的活动性；利用近震全波形拟合方法获得了主震及4次MS≥5.0地震的震源机制解和矩心深度，初步分析了本次地震序列的发震构造，获得如下主要结果：① 四川长宁余震序列呈NW−SE向分布，余震深度分布整体呈现出西深东浅的趋势，且西部地区地震的频度远远高于东部地区；② b值空间分布显示，震后长宁地区呈现出明显的挤压构造环境；③ 主震和4次震级较大余震的矩心深度均较浅，尽管均为逆冲型为主的地震事件，但破裂面走向有所差异；④ 推测主震及中强余震是长宁背斜地区既有断裂或者同震过程中所产生的新生断层长期受到外力挤压而错断所致。Abstract: The double difference earthquake location algorithm is used to relocate the earthquakes occurred in Changning area of Sichuan Province, which recorded by Sichuan regional network from January 1, 2019 to October 20, 2019, 7030 relocation events were obtained, and showing the clearer spatial distribution of Changning MS6.0 earthquake sequence. The average b-value of Changning focal area is calculated with relocated aftershocks catalog, and the seismicity of the earthquake sequence is analyzed. The focal mechanism solutions and centriod depth of the Changning main shock and 4 aftershocks with MS≥5.0 have been inverted with the local full-waveform inversion method, and the seismotectonics of this earthquake sequence was analyzed preliminarily. The main conclusions are as follow: ① The Sichuan Changning aftershocks distribute in a NW−SE trending, and the aftershocks show a trending of deep in the West and shallow in the East, and the frequency of earthquakes in the western part is much higher than that in the eastern part; ② The spatial distribution of b-value shows obvious compression tectonic environment in the Changning area after the occurrence of the earthquake; ③ The main shock and 4 moderate aftershocks occurred at unusual shallow centroid depths, and their focal plane solutions suggest that earthquakes occurred on thrust faults with slightly different strike; ④ It is speculated that the MS6.0 main shock and moderate aftershocks occurred on the preexisting faults, which subjected from a long-term compression force and the earthquake happened when the stress beyond the elastic limit, or the aftershocks generated on the newly generated faults created by mainshock coseismic rupture in Changning anticline area.
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Keywords:
- Changning earthquake /
- earthquake relocation /
- b-value /
- focal mechanism solution /
- seismo-tectonics
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图 1 研究区域构造背景及本研究涉及的台站和地震分布
（a） 区域构造背景和双差地震重定位及震源机制反演所用台站分布；（b） 长宁MS6.0地震主余震序列分布及兴文MS5.7地震和珙县MS5.3地震位置
Figure 1. Regional tectonic setting，seismic stations involved in this study and the distribution of earthquakes
（a） Regional tectonic setting and stations for double difference earthquake relocation and focal mechanism inversion； （b） The main shock and aftershock sequence of Changning MS6.0 earthquake and epicenters of Xingwen MS5.7 and Gongxian MS5.3 earthquakes
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图 2 本研究所用观测走时资料和速度模型
（a） 本研究所使用的P波和S波观测走时曲线图；（b） 地震重定位和震源机制反演采用的一维速度模型
Figure 2. The observed travel time data and velocity model for this study
（a） The observed travel time curves for P wave and S wave；（b） The 1D velocity model for earthquake relocation and focal mechanism inversion
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图 3 2019年1月1日至2019年10月20日长宁地区地震M−t图（a）和震源深度分布图（b）
Figure 3. M−t diagram （a） and distribution of focal depth （b） for earthquakes occurred in the Changning region from January 1 to October 20，2019
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图 4 长宁地震序列重定位震中分布与剖面图
（a） 重定位后地震平面分布；（b） 地震在剖面AA′ 上的投影，AA′ 为本研究所获得震源机制节面走向方向剖面；（c）−（e） 地震在BB′ ，CC′ 和DD′ 上的投影，BB′ ，CC′ 和DD′ 为垂直节面走向的剖面
Figure 4. The distribution of relocated Changning earthquake sequence in map view and cross-sections
（a） Relocated earthquakes in map view；（b） Earthquakes along the profile AA′ ，AA′ is the vertical cross section along the strike direction from focal mechanism solution；（c)−(e） Earthquakes along the profile BB′ ，CC′ and DD′ ，BB′ ，CC′ and DD′ are the vertical cross sections perpendicular to the strike direction from focal mechanism solution
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图 5 主震后12 h内不同时间段地震的平面及深度剖面
AA′ 为沿余震展布方向的纵剖面，不同颜色代表主震后每4 h的相对时间
Figure 5. Relocated earthquakes in map view and along cross section at different periods after the main shock
AA′ is the vertical cross section along the distribution direction of aftershock sequence， different colors denote relative times in every 4 hours after the main shock
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图 6 长宁MS6.0地震序列b值
（a） 长宁MS6.0地震震后平均b值；（b） 长宁MS6.0地震后b值空间分布
Figure 6. b-value for Changning MS6.0 earthquake sequence
（a） Mean b-value after Changning MS6.0 earthquake；（b） Spatial distribution of b-value in and around Changning MS6.0 earthquake source region
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图 7 长宁主震前后地震序列b值随时间的变化
Figure 7. Temporal variation of b-value before and after Changning MS6.0 earthquake
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图 8 长宁MS6.0地震观测与拟合波形相关系数随矩心深度的变化
Figure 8. The correlation between observed and synthetic waveforms of the Changning MS6.0 main shock versus the centroid depth
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图 9 长宁MS6.0地震主震震源机制解的拟合波形（红色）与观测波形（黑色）对比
台站 ROC，BJT，LBO的带通窗为 0.04—0.06 Hz；台站 WAS，XSB，YUB，XUW，SMI，GYA，JJS，BAX，XCO，HLI，ZFT的带通窗为 0.02—0.04 Hz。波形右上方数字为方差减少量，代表波形拟合程度
Figure 9. Comparison of observed （black） and synthetic （red） waveform for Changning MS6.0 main earthquake corresponding to optimum focal mechanism solution
Frequency of band-pass filter is 0.04—0.06 Hz for stations ROC，BJT，LBO，0.02—0.04 Hz for stations WAS，XSB，YUB，XUW，SMI，GYA，JJS，BAX，XCO，HLI，ZFT。The data on the upper right of the waveform is variance reduction，which represents for the degree of waveform fitting
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图 10 采用大折刀法分析震源参数不确定性
Figure 10. Analysis of source parameters uncertainty using Jackknife method
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图 11 长宁地震序列中MS≥5.0地震的震源机制解
Figure 11. Focal mechanism solutions of MS≥5.0 earthquake for Changning earthquake sequence
表 1 四川长宁MS6.0地震主余震序列中MS≥5.0地震的基本参数
Table 1 The basic earthquake parameters of MS≥5.0 earthquakes for Changning MS6.0 earthquake sequence
序号 发震时刻 北纬/° 东经/° 深度/km MS 年－月－日 时:分:秒 1 2019-06-17 22:55:43.2 28.34 104.90 16 6.0 2 2019-06-17 23:36:01.4 28.43 104.77 16 5.1 3 2019-06-18 07:34:33.7 28.37 104.89 17 5.3 4 2019-06-22 22:29:56.2 28.43 104.77 10 5.4 5 2019-07-04 10:17:58.6 28.41 104.74 8 5.6 
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表 2 长宁地震序列中5次MS≥5.0地震的震源机制解结果
Table 2 The focal mechanism solutions for five MS≥5.0 earthquakes of Changning earthquake sequence
编号 发震时刻 节面Ⅰ 节面Ⅱ 深度/km MS 走向/° 倾角/° 滑动角/° 走向/° 倾角/° 滑动角/° Evt1 2019-06-17 22:55:43.2 305 62 38 195 57 146 3.0 6.0 Evt2 2019-06-17 23:36:01.4 332 57 79 172 35 107 3.0 5.1 Evt3 2019-06-18 07:34:33.7 324 73 92 137 17 83 2.0 5.3 Evt4 2019-06-22 22:29:56.2 159 48 66 13 47 115 3.0 5.4 Evt5 2019-07-04 10:17:58.6 191 43 98 1 47 83 4.0 5.6
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蔡一川,程静馥. 2015. 四川长宁地区ML4.0以上地震震源机制解及震源深度反演[J]. 地震地磁观测与研究,3(6):14–18. Cai Y C,Cheng J F. 2015. Inversion of focal mechanism and focal depth of the earthquakes more than ML4.0 in Changning,Sichuan Province[J]. Seismological and Geomagnetic Observation and Research,3(6):14–18 (in Chinese).
韩佳东,杨建思,王伟平. 2019. 2017年西藏米林MS6.9地震余震序列重定位和b值时空分布特征[J]. 地震学报,41(2):169–180. doi: 10.11939/jass.20180077 Han J D,Yang J S,Wang W P. 2019. Relocation of the aftershock sequence of Milin MS6.9 earthquake in 2007 and spatio-temporal variation characteristics of b-value[J]. Acta Seismologica Sinica,41(2):169–180 (in Chinese).
何登发,鲁人齐,黄涵宇,王晓山,姜华,张伟康. 2019. 长宁页岩气开发区地震的构造地质背景[J]. 石油勘探与开发,46(5):993–1006. He D F,Lu R Q,Huang H Y,Wang X S,Jiang H,Zhang W K. 2019. Tectonic and geological background of the earthquake hazards in Changning shale gas development zone,Sichuan Basin,SW China[J]. Petroleum Exploration and Development,46(5):993–1006 (in Chinese).
梁姗姗,雷建设,徐志国,邹立晔,刘敬光. 2017. 2016年1月21日青海门源MS6.4余震序列重定位和主震震源机制解[J]. 地球物理学报,60(6):2091–2103. doi: 10.6038/cjg20170606 Liang S S,Lei J S,Xu Z G,Zou L Y,Liu J G. 2017. Relocation of the aftershock sequence and focal mechanism solutions of the 21 January 2016 Menyuan,Qinghai,MS6.4 earthquake[J]. Chinese Journal of Geophysics,60(6):2091–2103 (in Chinese).
梁姗姗,雷建设,徐志国,徐锡伟,邹立晔,刘敬光,陈宏峰. 2018. 2017年四川九寨沟MS7.0强震的余震重定位及主震震源机制反演[J]. 地球物理学报,61(5):2163–2175. doi: 10.6038/cjg2018L0508 Liang S S,Lei J S,Xu Z G,Xu X W,Zou L Y,Liu J G,Chen H F. 2018. Relocation of aftershocks of the 2017 Jiuzhaigou,Sichuan,MS7.0 earthquake and inversion for focal mechanism of the main shock[J]. Chinese Journal of Geophysics,61(5):2163–2175 (in Chinese).
刘静伟,吕悦军. 2016. 川滇地区b值空间分布特征及其与震源类型关系的初步探讨[J]. 震灾防御技术,11(3):561–572. doi: 10.11899/zzfy20160312 Liu J W,Lü Y J. 2016. Spatial distribution of b values and its relationship with the type of focal mechanism in the Sichuan-Yunnan area[J]. Technology for Earthquake Disaster Prevention,11(3):561–572 (in Chinese).
阮祥,程万正,张永久,李军,陈银. 2008. 四川长宁盐矿井注水诱发地震研究[J]. 中国地震,24(3):226–234. doi: 10.3969/j.issn.1001-4683.2008.03.004 Ruan X,Cheng W Z,Zhang Y J,Li J,Chen Y. 2008. Research of the earthquakes induced by water injections in salt mines in Changning,Sichuan[J]. Earthquake Research in China,24(3):226–234 (in Chinese).
史海霞,孟令媛,张雪梅,常莹,杨振涛,谢蔚云,服部克巳,韩鹏. 2018. 汶川地震前的b值变化[J]. 地球物理学报,61(5):1874–1882. doi: 10.6038/cjg2018M0024 Shi H X,Meng L Y,Zhang X M,Chang Y,Yang Z T,Xie W Y,Hattori K,Han P. 2018. Decrease in b value prior to the Wenchuan earthquake (MS8.0)[J]. Chinese Journal of Geophysics,61(5):1874–1882 (in Chinese).
王鹏,侯金欣,吴朋. 2017. 2017年九寨沟MS7.0地震序列活动特征分析[J]. 中国地震,33(4):453–462. doi: 10.3969/j.issn.1001-4683.2017.04.001 Wang P,Hou J X,Wu P. 2017. Temporal evolution of the seismicity of the 2017 Jiuzhaigou MS7.0 earthquake sequence[J]. Earthquake Research in China,33(4):453–462 (in Chinese).
王适择,李忠权,郭明,李洪奎. 2013. 川南长宁地区龙马溪组页岩裂缝发育特征[J]. 科学技术与工程,13(36):10887–10892. Wang S Z,Li Z Q,Guo M,Li H K. 2013. Developmental characteristics of Longmaxi formation shaly fissure in Changning of South of Sichuan area[J]. Science Technology and Engineering,13(36):10887–10892 (in Chinese).
王晓山,吕坚,谢祖军,龙锋,赵小艳,郑勇. 2015. 南北地震带震源机制解与构造应力场特征[J]. 地球物理学报,58(11):4149–4162. Wang X S,Lü J,Xie Z J,Long F,Zhao X Y,Zheng Y. 2015. Focal mechanisms and tectonic stress field in the North−South Seismic Belt of China[J]. Chinese Journal of Geophysics,58(11):4149–4162 (in Chinese).
王阎昭,王恩宁,沈正康,王敏,甘卫军,乔学军,孟国杰,李铁明,陶玮,杨永林,程佳,李鹏. 2008. 基于GPS资料约束反演川滇地区主要断裂现今活动速率[J]. 中国科学 D辑:地球科学,38(5):582–597. Wang Y Z,Wang E N,Shen Z K,Wang M,Gan W J,Qiao X J,Meng G J,Li T M,Tao W,Yang Y L,Cheng J,Li P. 2008. GPS-constrained inversion of present-day slip rates along major faults of the Sichuan−Yunnan region,China[J]. Science in China Series D:Earth Sciences,51(9):1267–1283. doi: 10.1007/s11430-008-0106-4
徐锡伟,闻学泽,郑荣章,马文涛,宋方敏,于贵华. 2003. 川滇地区活动块体最新构造变动样式及其动力来源[J]. 中国科学 (D辑),33 (增刊1):151–162. Xu X W,Wen X Z,Zheng R Z,Ma W T,Song F M,Yu G H. 2003. Pattern of latest tectonic motion and its dynamics for active blocks in Sichuan−yunnan region,China[J]. Science in China Series D:Earth Sciences,46(2):210–226.
徐志国,梁姗姗,邹立晔,刘敬光. 2019. 2016年12月8日新疆呼图壁MS6.2主震震源机制及余震序列定位[J]. 地震地质,41(1):44–57. doi: 10.3969/j.issn.0253-4967.2019.01.003 Xu Z G,Liang S S,Zou L Y,Liu J G. 2019. Mechanism of the 2016 Hutubi,Xinjiang,MS6.2 main shock and relocation of its aftershock sequences[J]. Seismology and Geology,41(1):44–57 (in Chinese).
易桂喜,龙峰,梁明剑,赵敏,王思维,宫悦,乔慧珍,苏金蓉. 2019. 2019年6月17日四川长宁MS6.0地震序列震源机制解与发震构造分析[J]. 地球物理学报,62(9):3432–3447. doi: 10.6038/cjg2019N0297 Yi G X,Long F,Liang M J,Zhao M,Wang S W,Gong Y,Qiao H Z,Su J R. 2019. Focal mechanism solutions and seismogenic structure of the 17 June 2019 MS6.0 Sichuan Changning earthquake sequence[J]. Chinese Journal of Geophysics,62(9):3432–3447 (in Chinese).
张广伟,雷建设,梁姗姗,孙长青. 2014. 2014年8月3日云南鲁甸MS6.5级地震序列重定位与震源机制研究[J]. 地球物理学报,57(9):3018–3027. doi: 10.6038/cjg20140926 Zhang G W,Lei J S,Liang S S,Sun C Q. 2014. Relocations and focal mechanism solutions of the 3 August 2014 Ludian,Yunnan MS6.5 earthquake sequence[J]. Chinese Journal of Geophysics,57(9):3018–3027 (in Chinese).
张广伟. 2016. 云南地区地震的重新定位及b值研究[J]. 中国地震,32(1):54–62. doi: 10.3969/j.issn.1001-4683.2016.01.005 Zhang G W. 2016. Research on earthquake relocation and b-value in the Yunnan area[J]. Earthquake Research in China,32(1):54–62 (in Chinese).
Aki K. 1965. Maximum likelihood estimate of b in the formula logN =a-bM and its confidence limits[J]. Bull Earthq Res Instit,Univ Tokyo,43(2):237–239.
Bouchon M. 1981. A simple method to calculate Green's functions for elastic layered media[J]. Bull Seismol Soc Am,71(4):959–971.
Boyd O S,Dreger D S,Lai V H,Gritto R. 2015. A systematic analysis of seismic moment tensor at the Geysers geothermal field,California[J]. Bull Seismol Soc Am,105(6):2969–2986. doi: 10.1785/0120140285
Goebel T H W,Kwiatek G,Becker T W,Brodsky E E,Dresen G. 2017. What allows seismic events to grow big? Insights from b-value and fault roughness analysis in laboratory stick-slip experiments[J]. Geology,45(9):815–818. doi: 10.1130/G39147.1
Kennett B L N,Kerry N J. 1979. Seismic waves in a stratified half space[J]. Geophysical Journal International,57(3):557–583. doi: 10.1111/j.1365-246X.1979.tb06779.x
Lei X L,Huang D J,Su J R,Jiang G M,Wang X L,Wang H,Guo X,Fu H. 2017. Fault reactivation and earthquakes with magnitudes of up to MW4.7 induced by shale-gas hydraulic fracturing in Sichuan Basin,China[J]. Sci Rep,7:7971. doi: 10.1038/s41598-017-08557-y
Marzocchi W,Sandri L. 2009. A review and new insights on the estimation of the b-value and its uncertainty[J]. Ann Geophy,46(6):1271–1282.
Scholz C H. 1968. The frequency-magnitude relation of microfracturing in rock and its relation to earthquakes[J]. Bull Seismol Soc Am,58(1):399–415.
Schorlemmer D,Wiemer S,Wyss M. 2005. Variations in earthquake-size distribution across different stress regimes[J]. Nature,437(7058):539–542. doi: 10.1038/nature04094
Shi Y L,Bolt B A. 1982. The standard error of the magnitude-frequency b value[J]. Bull Seismol Soc Am,72(5):1677–1687.
Sokos E N,Zahradnik J. 2008. ISOLA a fortran code and a Matlab GUI to perform multiple-point source inversion of seismic data[J]. Comput Geosci-uk,34(8):967–977. doi: 10.1016/j.cageo.2007.07.005
Waldhauser F,Ellsworth W L. 2000. A double-difference earthquake location algorithm:Method and application to the Northern Hayward fault,California[J]. Bull Seismol Soc Am,90(6):1353–1368. doi: 10.1785/0120000006
Wiemer S. 2001. A software package to analyze seismicity:ZMAP[J]. Seismol Res Lett,72(3):373–382. doi: 10.1785/gssrl.72.3.373
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