摘要
九寨沟余震序列的震源机制和构造应力场有助于认识本次地震的发震构造和孕震机理。本文基于四川区域地震台网的波形资料,采用波形拟合(CAP)方法和P波初动+振幅比(HASH)方法反演得到2017年8月8日九寨沟7.0级地震序列中59次M_L≥3.0地震的震源机制解,并基于该结果采用阻尼线性逆推法(DRSSI),计算研究区域的平均构造应力场,给出该区域的应力场特征。结果显示,利用CAP方法反演得到的本次主震的最佳双力偶机制解节面I:走向248°/倾角86°/滑动角–169°,节面II:走向157°/倾角79°/滑动角–4°,矩震级为Mw6.31,矩心深度5 km,属走滑型地震事件;大部分余震的震源机制解错动类型与主震一致,矩心深度集中在3~10 km;应力场反演结果显示,该区域周边的应力性质为走滑型,最大主应力方向呈NWW–SEE向,与该区域的应力场方向一致,表明本次地震主要受区域应力的控制。结合该区域的地震地质构造等已有研究成果,分析认为此次地震的发震断层为走向NW–SE、倾向SW的左旋走滑断裂——树正断裂,巴颜喀拉块体向E-SE向的水平运动受到华南块体的强烈阻挡导致此次地震的发生,汶川地震的发生对本次地震具有一定的促进作用。
Focal mechanism solutions and stress field for the 2017 M_s7.0 Jiuzhaigou earthquake sequence can help to understand the seismogenic structure and mechanism. Based on the digital waveforms of Sichuan seismic network, the authors calculated focal mechanisms of the Jiuzhaigou earthquake sequence of 59 M_L≥3.0 by employing the CAP method and HASH method, and then used the focal mechanism solutions to calculate the stress field through the DRSSI. The nodal plane parameters of the main event are as follows: strike=248°, dip=86°, rake = –169°, and strike =157°, dip=79°, rake = –4°, the moment magnitude of the main shock is 6.31 and the depth is about 5 kilometers, suggesting a strike-slip seismic event. The type of focal mechanisms of ML≥3.0 aftershocks is consistent with the main shock, the depths of the Jiuzhaigou earthquake sequence are between 3 and 10 kilometers. The stress regime around the epicenter area is of the strike-slip type, and the maximum dominant direction is near NWW–SEE, almost consistent with that of the type of focal mechanisms, which shows that the occurrence of the earthquake was mainly controlled by regional stress. In combination with the seismic geological structure, the authors hold that the MS7.0 Jiuzhaigou earthquake was formed by the NW–SE trending SW dipping Shuzheng fault. The E–SE trending horizontal movement of the block of the Bayan Har was strongly blocked by the South China Block, which probably led to the occurrence of this earthquake.
引文
付俊东,任金卫,张军龙,熊仁伟,杨攀新,陈长云,胡朝忠.2012.东昆仑断裂带东段塔藏断裂晚第四纪古地震研究[J].第四纪研究,32(3):473-483.
胡朝忠,任金卫,杨攀新,熊仁伟,陈长云,付俊东.2017.东昆仑断裂东端塔藏断裂压剪活动与高原隆升作用讨论[J].地质学报,91(7):1401-1415.
季灵运,刘传金,徐晶,刘雷,龙锋,张致伟.2017.九寨沟MS7.0地震的InSAR观测及发震构造分析[J].地球物理学报,60(10):4069-4082.
阚荣举,张四昌,晏凤桐,俞林胜.1977.我国西南地区现代构造应力场与现代构造活动特征的探讨[J].地球物理学报,20(2):96-109.
李金,王琼,吴传勇,向元.2016.2015年7月3日皮山6.5级地震发震构造初步研究[J].地球物理学报,59(8):2859-2870.
李勇,邵崇建,李芃宇,周荣军,刘玉法,张威,马超,颜照坤,闫亮,王伟明.2017.九寨沟Ms7.0级地震的左旋走滑作用与动力机制[J].成都理工大学学报(自然科学版),44(6):641-648.
罗艳,赵里,曾祥方,高原.2015.芦山地震序列震源机制及其构造应力场空间变化[J].中国科学:地球科学,45(4):538-550.
M7专项工作组.2012.中国大陆大地震中-长期危险性研究[M].北京:地震出版社.
庞亚瑾,程惠红,张怀,石耀霖.2017.巴颜喀拉块体东缘形变及九寨沟地震孕震环境数值分析[J].地球物理学报,60(10):4046-4055.
祁玉萍,李闽峰,李圣强,王斌,刘桂平,肖本夫,江鹏.2015.准实时中小地震震源机制波形自动反演系统的构建及在首都圈地区的应用[J].地震,35(4):99-108.
任俊杰,徐锡伟,张世民,罗毅,梁欧博,赵俊香.2017.东昆仑断裂带东端的构造转换与2017年九寨沟MS7.0地震孕震机制[J].地球物理学报,60(10):4027-4045.
屈新建,曲春燕,龚文瑜,赵德政,张迎峰,张国宏,宋小刚,刘云华,张桂芳.2017.2017年8月8日四川九寨沟7.0级地震InSAR同震形变场及断层滑动分布反演[J].地球物理学报,60(12):4527-4536.
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.
徐锡伟,陈桂华,王启欣,陈立春,任治坤,许冲,魏占玉,鲁人齐,谭锡斌,董绍鹏,石峰.2017a.九寨沟地震发震断层属性及青藏高原东南缘现今应变状态讨论[J].地球物理学报,60(10):4018-4026.
徐锡伟,吴熙彦,于贵华,谭锡斌,李康.2017b.中国大陆高震级地震危险区判定的地震地质学标志及其应用[J].地震地质,39(2):219-275.
杨宜海,范军,花茜,高见,王朝亮,周鲁,赵韬.2017.近震全波形反演2017年九寨沟M7.0地震序列震源机制解[J].地球物理学报,60(10):4098-4104.
杨智娴,陈运泰,苏金蓉,陈天长,吴朋.2012.2008年5月12日汶川MW7.9地震的震源位置与发震时刻[J].地震学报,34(2):127-136.
姚鑫,周振凯,李凌婧,刘星洪,姚佳明.2017.2017年四川九寨沟MS7.0地震InSAR同震形变场及发震构造探讨[J].地质力学学报,23(4):507-514.
易桂喜,龙锋,VALLAGEA,KLINGERY,梁明剑,王思维.2016.2013年芦山地震序列震源机制与震源区构造变形特征分析[J].地球物理学报,59(10):3711-3731.
易桂喜,龙锋,梁明剑,张会平,赵敏,叶有清,张致伟,祁玉萍,王思维,宫悦,乔惠珍,汪智,邱桂兰,苏金蓉.2017.2017年8月8日九寨沟M7.0地震及余震震源机制解与发震构造分析[J].地球物理学报,60(10):4083-4097.
易桂喜,龙锋,闻学泽,梁明剑,王思维.2015.2014年11月22日康定MW6.3级地震序列发震构造分析[J].地球物理学报,58(4):1205-1219.
张岳桥,杨农,施炜,董树文.2008.青藏高原东缘新构造及其对汶川地震的控制作用[J].地质学报,82(12):1668-1678.
赵小麟,邓起东,陈社发.1994.龙门山逆断裂带中段的构造地貌学研究[J].地震地质,16(4):422-428.
赵珠,张润生.1987.四川地区地震波分区走时表的编制[J].四川地震,(3):29-35.
钟继茂,程万正.2006.由多个地震震源机制解求川滇地区平均应力场方向[J].地震学报,28(4):337-346,450.
周荣军,蒲晓虹,何玉林,黎小刚,戈天勇.2000.四川岷江断裂带北段的新活动、岷山断块的隆起及其与地震活动的关系[J].地震地质,22(3):285-294.
朱航,屈勇.2017.九寨沟MS7.0地震静态库仑应力触发及对附近断层影响分析[J].中国地震,33(4):471-479.
朱航,闻学泽.2009.1973~1976年四川松潘强震序列的应力触发过程[J].地球物理学报,52(4):994-1003.
ANGELIER J,TARANTOLA A,VALETTE B,MANOUSSIS S.1982.Inversion of field data in fault tectonics to obtain the regional stress.single phase fault populations:A new method of computing the stress tensor[J].Geophys.J.R.astr.Soc,69(3):607-621.
ANGELIER J.1979.Determination of the mean principal direction of stresses for a given fault population[J].Tectonophysics,56(3):17-26.
CHEN S F,WILSON C J L,DENG Qi-dong.1994.Active faulting and block movement associated with large earthquakes in the Minshan and Longmen mountains,northeastern Tibetan plateau[J].Journal of Geophyscial Research:Solid Earth,99(B12):24025-24038.
FROHLICH C.2001.Display and quantitative assessment of distributions of earthquake focal mechanism[J].Geophysical Journal International,144(2):300-308.
FU Jun-dong,REN Jin-wei,ZHANG Jun-long,XIONG Ren-wei,YANG Pan-xin,CHEN Chang-yun,HU Chao-zhong.2012.Research on late Quaternary pale earthquake on Tazang Fault on the eastern section of the Kunlun active fault[J].Quaternary Sciences,32(3):473-483(in Chinese with English abstract).
GAN W J,ZHANG P Z,SHEN Z K,NIU Z J,WANG M,WAN YG,ZHOU D M,CHENG J.2007.Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements[J].Journal of Geophysical Research,112(B08416):1-14.
GEPHART J W,FORSYTH D W.1984.An improved method for determining the regional stress tensor using earthquake focal mechanism data:application to the San Fernando Earthquake Sequence[J].Journal of Geophysical Research,89(B11):9305-9320.
HARDEBECK J L,MICHAEL A J.2006.Damped regional-scale stress inversions:Methodology and examples for southern California and the Coalinga aftershock sequence[J].Journal ofGeophysical Research,111:B11310.
HARDEBECK J L,SHEARER P M.2002.A new method for determining first-motion focal mechanisms[J].Bulletin of the Seismological Society America,92(6):2264-2276.
HU Chao-zhong,REN Jin-wei,YANG Pan-xin,XIONG Ren-wei,CHEN Chang-yun,FU Jun-dong.2017.Discussion on the Compression-shear activity of the Tazang fault in East Kunlun and uplift of plateau[J].Acta Geologica Sinica,91(7):1401-1415(in Chinese with English abstract).
JI Ling-yun,LIU Chuan-jin,XU Jing,LIU Lei,LONG Feng,ZHANG Zhi-wei.2017.InSAR observation and inversion of the seismogenic fault for the 2017 Jiuzhaigou MS7.0 earthquake in China[J].Chinese Journal of Geophysics,60(10):4069-4082(in Chinese with English abstract).
KAN Rong-ju,ZHANG Si-chang,YAN Feng-tong,YU Lin-sheng.1977.Present tectonic stress field and its relation to the characteristics of recent tectonic activity in southwestern China[J].Chinese Journal of Geophysics,20(2):96-109(in Chinese with English abstract).
LI Jin,WANG Qiong,WU Chuan-yong,XIANG Yuan.2016.Preliminary study for seismogenic structure of the Pishan MS6.5earthquake of July 3,2015[J].Chinese Journal of Geophysics,59(8):2859-2870(in Chinese with English abstract).
LI Yong,SHAO Chong-jian,LI Peng-yu,ZHOU Rong-jun,LIUYu-fa,ZHANG Wei,MA Chao,YAN Zhao-kun,YAN Liang,WANG Wei-ming.2017.Left-lateral strike-slip effect and dynamic mechanism of the Jiuzhaigou Ms7.0 eqrthquake in the eastern margin of Tibetan Plateau,China[J].Journal of Chengdu University of Technology,44(6):641-648(in Chinese with English abstract).
LUO Yan,ZHAO Li,ZENG Xiang-fang,GAO Yuan.2015.Focal mechanisms of the Lushan earthquake sequence and spatial variation of the stress field[J].Science China:Earth Sciences,45(4):538-550(in Chinese with English abstract).
MICHAEL A J.1987.Use of focal mechanisms to determine stress:A control study[J].Journal of Geophysical Research,92(B1):357-368.
MICHAEL A J.1991.Spatial variations in stress within the 1987Whittier Narrows,California,aftershock sequence:New techniques and results[J].Journal of Geophysical Research,96(B4):6303-6319.
PANG Ya-jin,CHENG Hui-hong,ZHANG Huai,SHI Yao-lin.2017.Numberical modeling of crustal deformation in the eastern margin of the Bayan Har block and analysis of seismogenic environment of the 2017 Jiuzhaigou earthquake[J].Chinese Journal of Geophysics,60(10):4046-4055(in Chinese with English abstract).
PATRICIA M G,GRZEGORZ K,MICHELE L,MACRO B.2014.MSATSI:A MATLAB package for stress inversion combining solid classic methodology,a new simplified user-handling,and a visualization tool[J].Seismological Research Letters,85(4):1-9.
QI Yu-ping,LI Min-feng,LI Sheng-qiang,WANG Bin,LIUGui-ping,XIAO Ben-fu,JIANG Peng.2015.Quasi-automatic waveform inversion for focal mechanisms of small to moderate earthquakes and its application in the capital area[J].Earthquake,35(4):99-108(in Chinese with English abstract).
REN Jun-jie,XU Xi-wei,ZHANG Shi-min,LUO Yi,LIANGOu-bo,ZHAO Jun-xiang.2017.Tectonic transformation at the eastern termination of the Eastern Kunlun fault zone and seismogenic mechanism of the 8 August 2017 Jiuzhaigou MS7.0 earthquake[J].Chinese Journal of Geophysics,60(10):4027-4045(in Chinese with English abstract).
SEEBER L,ARMBRUSTER J G.2000.Earthquakes as beacons of stress change[J].Nature,407(6800):69-72.
SHAN Xin-jian,QU Chun-yan,GONG Wen-yu,GONG Wen-yu,ZHAO De-zheng,ZHANG Ying-feng,ZHANG Guo-hong,SONG Xiao-gang,LIU Yun-hua,ZHANG Gui-fang.2017.Coseismic deformation field of the Jiuzhaigou MS7.0earthquake from Sentinel-1 A InSAR data and fault slip inversion[J].Chinese Journal of Geophysics,60(12):4527-4536(in Chinese with English abstract).
TAN Y,HELEMBERGER D.2007.A new method for determining small test earthquake source parameters using short-period Pwaves[J].Bulletin of the Seismological Society America,97(4):1176-1195.
TODA S,LIN J,MEGHRAOUI M,STEIN R S.2008.12 May2008 M=7.9 Wenchuan,China,earthquake calculated to increase failure stress and seismicitiy rate on three major fault systems[J].Geophysical Research Letters,L17305.
WANG Xiao-shan,LIU Jian,XIE Zu-jun,LONG Feng,ZHAOXiao-yan,ZHENG Yong.2015.Focal mechanisms and tectonic stress field in the North-South Seismic Belt of China[J].Chinese Journal of Geophysics,58(1):4149-4162(in Chinese with English abstract).
WEN X Z,YI G X,XU X W.2007.Background and precursory seismicities along and surrounding the kunlun fault before the MS8.1,2001,Kokoxili Earthquke,China[J].Journal of Asian Earth Science,30(1):63-72.
WESSEL P,SMITH W H F.1991.Frees of tware helps map and display data[M].Eos Trans AGU,72(41):441.
Working Group of M7.2012.Study on the mid-to long-term potential of large earthquakes on the Chinese Continent[M].Beijing:Seismological Press(in Chinese with English abstract).
XU Xi-wei,CHEN Gui-hua,WANG Qi-xin,CHEN Li-chun,RENZhi-kun,XU Chong,WEI Zhan-yu,LU Ren-qi,TAN Xi-bin,DONG Shao-peng,SHI Feng.2017a.Discussion on seismogcnic structure of Jiuzhaigou earthquake and its implication for current strain state in the southeastern Qinghai-Tibet Plateau[J].Chinese Journal of Geophysics,60(10):4018-4026(in Chinese with English abstract).
XU Xi-wei,WU Xi-yan,YU Gui-hua,TAN Xi-wei,LI Kang.2017b.Seismo-geological signatures for identifying M≥7.0earthquake risk areas and their preliminary application in mainland China[J].Seismology and Geology,39(2):219 -275(in Chinese with English abstract).
YANG Yi-hai,FAN Jun,HUA Qian,GAO Jian,WANGChao-liang,ZHOU Lu,ZHAO Tao.2017.Inversion for the focal mechanisms of the 2017 Jiuzhaigou M7.0 earthquake sequence using near-field full waveforms[J].Chinese Journal of Geophysics,60(10):4098-4104(in Chinese with English abstract).
YANG Zhi-xian,CHEN Yun-tai,SU Jin-rong,CHEN Tian-chang,WU Peng.2012.The hypocenter and origin time of the Mw7.9Wenchuan earthquake of May 12,2008[J].Acta Seismologica Sinica,34(2):127-136(in Chinese with English abstract).
YAO Xin,ZHANG Zheng-kai,LI Ling-jing,LIU Xing-hong,YAOJia-ming.2017.InSAR co-seismic deformation of 2017 MS7.0Jiuzhaigou earthquake and disscussions on seismogenic tectonics[J].Journal of Geomechanics,23(4):507-514(in Chinese with English abstract).
YI Gui-xi,LONG Feng,AMAURY V,YANN KLINGER,LIANGMing-jian,WANG Si-wei.2016.Focal mechanism and tectonic deformation in the seismogenic area of the the 2013Lushan earthquake sequence,southwestern China[J].Chinese Journal of Geophysics,59(10):3711-3731(in Chinese with English abstract).
YI Gui-xi,LONG Feng,LIANG Ming-jian,ZHANG Hui-ping,ZHAO Min,YE You-qing,ZHANG Zhi-wei,QI Yu-ping,WANG Si-wei,GONG Yue,QIAO Hui-zhen,WANG Zhi,QIU Gui-lan,SU Jin-rong.2017.Focal mechanism solutions and seismogenic structure of the 8 August 2017 M7.0 Jiuzhaigou earthquake and its aftershocks,northern Sichuan[J].Chinese Journal of Geophysics,60(10):4083-4097(in Chinese with English abstract).
YI Gui-xi,LONG Feng,WEN Xue-ze,LIANG Ming-jian,WANGSi-wei.2015.Seismogenic structure of the M6.3 Kangding earthquake sequence on 22 Nov.2014,Southwest China[J].Chinese Journal of Geophysics,58(4):1205-1219(in Chinese with English abstract).
ZHANG Yue-qiao,YANG Nong,SHI Wei,DONG Shu-wen.2008.Neotectonics of eastern Tibet and its control on Wenchuan earthquake[J].Acta Geological Sinica,82(12):1668-1678(in Chinese with English abstract).
ZHAO L S,HELEMBERGER D V.1994.Source estimation from broadband regional seismograms[J].Bulletin of the Seismological Society America Bulletin of the Seismological Society America,84:91-104.
ZHAO L,LUO Y,LIU T Y,LUO Y J.2013.Earthquake focal mechanisms in Yunnan and their inference on the regional stress field[J].Bulletin of the Seismological Society America,103(4):2498-2507.
ZHAO Xiao-ling,DENG Qi-dong,CHEN She-fa.1994.Tectonic geomorphology of the central segment of the Longmenshan trust belt,western Sichuan southwestern China[J].Seismology and Geology,16(4):422-428(in Chinese with English abstract).
ZHAO Zhu,ZHANG Rui-sheng.1987.The compilation of regional travel time table in Sichuan[J].Earthquake Research in Sichuan,(3):29-35(in Chinese with English abstract).
ZHONG Ji-mao,CHENG Wan-zheng.2006.Determination of directions of the mean stress field in Sichuan-Yunnan region from a number of focal mechanism solutions[J].Acta Seismologica Sinica,19(4):359-369,450(in Chinese with English abstract).
ZHOU Rong-jun,PU Xiao-hong,HE Yu-lin,LI Xiao-gang,GETian-yong.2000.Recent activity of Minjiang Fault zone uplift of minshan block and their relationship with sesmicity of Sichuan[J].Seismology and Geology,19(2):115-124(in Chinese with English abstract).
ZHU Hang,QU Yong.2017.Analysis on the triggering of the Jiuzhaigou MS7.0 earthquake's static Coulomb stress and its influences on its adjacent faults[J].Earthquake Research in China,33(4):471-479(in Chinese with English abstract).
ZHU Hang,WEN Xue-ze.2009.Stress triggering process of the1973 to 1976 Sonpan,Sichuan,sequence of strong earthquakes[J].Chinese Journal of Geophysics,52(4):994-1003(in Chinese with English abstract).
ZHU L P,HELEMBERGER D V.1996.Advancement in source estimation technique using broad-bandregional seismograms[J].Bulletin of the Seismological Society America,86:1634-1641.
ZHU L P,RIVERA L A.2002.A note on the dynamic and static displacement from a pointsource in multilayered media[J].Geophysical Journal International,148:619-627.