2013年4月20日四川芦山M_S7.0地震:一个高角度逆冲地震
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摘要
利用中国地震台网和IRIS数据中心提供的近远震数字地震波形记录,首先读取P波初动方向,在考虑深度误差和速度模型引起的离源矢量误差基础上,利用网格搜索方法,计算了2013年4月20日四川芦山MS7.0地震断层面解,其断层面走向/倾角/滑动角依次为212°/44°/92°.然后采用近远震波形联合反演方法(CAPjoint),反演了地震矩心深度和点源近似下双力偶解,表明地震发生在12km深度,发震断层面参数为212°/47°/93°.通过分析波形反演中深度和震源区地震波速度模型对断层面倾角的影响,并结合短期余震机制解,认为芦山MS7.0地震是一个高角度逆冲地震.
P wave first motions picked from regional and teleseismic records were used to invert focal mechanism of the Lushan MS7.0 earthquake on 20 April 2013.To reduce errors introduced by uncertainties of take-off angle due to the velocity model and focal depth errors,random perturbations of take-off angle were added into raw values.After multiple trials,strike/dip/rake angles of the best solution are calculated to be 212°/44°/92°.To better understand focal mechanism,the regional and teleseismic waveforms inversion method(CAPjoint) was employed to determine the centroid depth,double-couple solution and magnitude.The results(212°/47°/93°,depth=12 km,Mw6.7) suggest that the Lushan earthquake is a high-angle thrust event.Both inversion results with three other seismic velocity models and focal mechanisms of short term aftershocks support this solution.
P wave first motions picked from regional and teleseismic records were used to invert focal mechanism of the Lushan MS7.0 earthquake on 20 April 2013.To reduce errors introduced by uncertainties of take-off angle due to the velocity model and focal depth errors,random perturbations of take-off angle were added into raw values.After multiple trials,strike/dip/rake angles of the best solution are calculated to be 212°/44°/92°.To better understand focal mechanism,the regional and teleseismic waveforms inversion method(CAPjoint) was employed to determine the centroid depth,double-couple solution and magnitude.The results(212°/47°/93°,depth=12 km,Mw6.7) suggest that the Lushan earthquake is a high-angle thrust event.Both inversion results with three other seismic velocity models and focal mechanisms of short term aftershocks support this solution.
引文
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[9]陈伟文,倪四道,汪贞杰等.2010年高雄地震震源参数的近远震波形联合反演.地球物理学报,2012,55(7):2319-2328.Chen W W,Ni S D,Wang Z J,et al.Joint inversion with both local and teleseismic waveforms for source parameters of the2010Kaohsiung earthquake.Chinese J.Geophys.(in Chinese),2012,55(7):2319-2328.
[10]Kikuchi M,Kanamori H.Inversion of complex body waves.Bulletin of the Seismological Society of America,1982,72(2):491-506.
[11]Zhu L,Rivera L A.A note on the dynamic and static displacements from a point source in multilayered media.Geophysical Journal International,2002,148(3):619-627.
[12]曾祥方,韩立波,石耀霖.四川芦山M s 7.0地震震源机制解初步研究.科技导报.2013,31(14):5-8.Zeng X F,Han L B,Shi Y L.Focal mechanism of Lushan M s 7.0Earthquake,April20,2013.Science and Technology Servies.2013,31(14):5-8.
[13]刘启元,李昱,陈九辉等.汶川M s 8.0地震:地壳上地幔S波速度结构的初步研究.地球物理学报,2009.52(2),309-319.Liu Q Y,Li Y,Chen J H,et al.Wenchuan M S 8.0 earthquake:preliminary study of the S-wave velocity structure of the crust and upper mantle.Chinese J.Geophys.(in Chinese),2009,52(2):309-319.
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[15]雷建设,赵大鹏,苏金蓉等.龙门山断裂带地壳精细结构与汶川地震发震机理.地球物理学报,2009,52(2):339-345.Lei J S,Zhao D P,Su J R,et al.Fine seismic structure under the Longmengshan fault zone and the mechanism of large Wenchuan earthquake.Chinese J.Geophys.(in Chinese),2009,52(2):339-345.
[16]Li Z W,Ni S D,Hao T Y,et al.Uppermost mantle structure of the eastern margin of the Tibetan plateau from interstation Pn traveltime difference tomography.Earth and Planetary Science Letters,2012.335-336:195-205.
[17]钟继茂,程万正.由多个地震震源机制解求川滇地区平均应力场方向.地震学报,2006,28(4):337-346.Zhong J M,Cheng W Z.Determination of directions of the mean stress field in Sichuan-Yunnan region from a number of focal mechanism solutions.Acta Seismologica Sinica(in Chinese),2006,28(4):337-346.
[18]秦向辉,陈群策,谭成轩等.龙门山断裂带西南段现今地应力状态与地震危险性分析.岩石力学与工程学报,2013,32(增1):2870-2876.Qin X H,Chen Q C,Tan C X,et al.Analysis of current geostress state and seismic risk in southwest segment of Longmenshan fracture belt.Chinese Journal of Rock Mechanics and Engineering(in Chinese),2013,32(S1):2870-2876.
[19]万柯松,倪四道,赵里.龙门山周边地区地震波速度结构的有限频率反演.国际地震动态,2010,6:16-16.Wan K S,Ni S D,Zhao L.Finite frequency waveform inversion for velocity structure in Longmengshan area.Recent Developments in World Seismology(in Chinese),2010,6:16-16
[20]谢军,倪四道,曾祥方.四川盆地中部浅层地壳一维剪切波速度结构初步研究.四川地震,2012,143(2):20-24.Xie J,Ni S D,Zeng X F.1Dshear wave velocity structure of the shallow upper crust in central Sichuan Basin.Earthquake Research in Sichuan(in Chinese),2012,143(2):20-24.
[21]王椿镛,吴建平,楼海等.川西藏东地区的地壳P波速度结构.中国科学(D辑),2003,33(增刊):181-189.Wang C Y,Wu J P,Lou H,et al.P-wave velocity structure in western Sichuan and eastern Tibetan region.Sci.China Ser.D-Earth Sci.,2003,46(Suppl.):254-265.
[22]杨晓平,蒋溥,宋方敏等.龙门山断裂带南段错断晚更新世以来地层的证据.地震地质,1999,21(4):341-345.Yang X P,Jiang P,Song F M,et al.The evidence of the south Longmenshan fault zones cutting late Quaternary stratum.Seismology and Geology(in Chinese),1999,21(4):341-345.
[23]周永胜,何昌荣.汶川地震区的流变结构与发震高角度逆断层滑动的力学条件.地球物理学报,2009,52(2):474-484.Zhou Y C,He C R.The rhelogical structure of crust and mechanics of high-angle reverse fault slip for Wenchuan Ms8.0 earthquake.Chinese J.Geophys.(in Chinese),2009,52(2):474-484.
[24]柳畅,朱伯靖,石耀霖.粘弹性数值模拟龙门山断裂带应力积累及大震复发周期.地质学报,2012,86(1):157-169.Liu C,Zhu B J,Shi Y L.Stress accumulation of the Longmenshan Fault and recurrence interval of Wenchuan Earthquake based on viscoelasticity simulation.Acta Geologica Sinica(in Chinese),2012,86(1):157-169.
[25]单斌,熊熊,郑勇等.2008年5月12日M w 7.9汶川地震导致的周边断层应力变化.中国科学(D辑),2009,39(5):527-545.Shan B,Xiong X,Zheng Y,et al.Stress changes on major faults caused by Mw7.9Wenchuan earthquake,May12,2008.,Sci.China Ser.D-Earth Sci.,2009,52(5):593-601.601.
[26]邵志刚,周龙泉,蒋长胜等.2008年汶川M S 8.0地震对周边断层地震活动的影响.地球物理学报,2010,53(8):1784-1795.Shao Z G,Zhou L Q,Jiang C S,et al.The impact of Wenchuan M s 8.0earthquake on the seismicity of surrounding faults.Chinese J.Geophysi.(in Chinese),2010,53(8):1784-1795.
[27]石耀霖,曹建玲.库仑应力计算及应用过程中若干问题的讨论—以汶川地震为例.地球物理学报,2010,53(1):102-110.Shi Y L,Cao J L.Some aspects in static stress change calculation-case study on Wenchuan earthquake.Chinese J.Geophys.(in Chinese),2010,53(1):102-110.
[2]王卫民,郝金来,姚振兴.2013年4月20日四川芦山地震震源破裂过程反演初步结果.地球物理学报,2013,56(4):1412-1417,doi:10.6038/cjg20130436.Wang W M,Hao J L,Yao Z X.Preliminary result for rupture process of Apr.20,2013,Lushan Earthquake,Sichuan,China.Chinese J.Geophys.(in Chinese),2013,56(4):1412-1417,doi:10.6038/cjg20130436.
[3]邓起东,张培震,冉勇康等.中国活动构造基本特征.中国科学(D辑),2002,32(12):1020-1030.Dong Q D,Zhang P Z,Ran Y K,et al.Basic feature of China active structures.Sci.China Ser.D-Earth Sci.(in Chinese),2002,32(12):1020-1030.
[4]许忠淮,汪素云,黄雨蕊等.由大量地震资料推断的我国大陆构造应力场.地球物理学报,1989,32(6):636-647.Xu Z H,Wang S Y,Huang Y R,et al.The tectonic stress field of Chinese continent deduced from a great number of earthquakes.Chinese J.Geophys.(in Chinese),1989,32(6):636-647.
[5]郑秀芬,欧阳飚,张东宁等.“国家数字测震台网数据备份中心”技术系统建设及其对汶川大地震研究的数据支撑.地球物理学报,2009,52(5):1412-1417.Zheng X F,Ouyyang B,Zhang D N,et al.Technical systerm construction of Data Backup Centre for China Seismograph Network and the data support to researches on the Wenchuan earthquake.Chinese J.Geophysi.(in Chinese),2009,52(5):1412-1417.
[6]郑勇,马宏生,吕坚等.汶川地震强余震(M s≥5.6)的震源机制解及其与发震构造的关系.中国科学(D辑),2009,39(4):413-426.Zheng Y,Ma H W,Lu J,et al.Source mechanism of strong aftershock for seismotectonic.Sci.China Ser.D-Earth Sci.(in Chinese),2009,39(4):413-426.
[7]Hardebeck J L,Shearer P M.A new method for determining first-motion focal mechanisms.Bulletin of the Seismological Society of America,2002,92(6):2264-2276.
[8]Zhu L,Helmberger D V.Advancement in source estimation techniques using broadband regional seismograms.Bulletin of the Seismological Society of America,1996,86(5):1634-1641.
[9]陈伟文,倪四道,汪贞杰等.2010年高雄地震震源参数的近远震波形联合反演.地球物理学报,2012,55(7):2319-2328.Chen W W,Ni S D,Wang Z J,et al.Joint inversion with both local and teleseismic waveforms for source parameters of the2010Kaohsiung earthquake.Chinese J.Geophys.(in Chinese),2012,55(7):2319-2328.
[10]Kikuchi M,Kanamori H.Inversion of complex body waves.Bulletin of the Seismological Society of America,1982,72(2):491-506.
[11]Zhu L,Rivera L A.A note on the dynamic and static displacements from a point source in multilayered media.Geophysical Journal International,2002,148(3):619-627.
[12]曾祥方,韩立波,石耀霖.四川芦山M s 7.0地震震源机制解初步研究.科技导报.2013,31(14):5-8.Zeng X F,Han L B,Shi Y L.Focal mechanism of Lushan M s 7.0Earthquake,April20,2013.Science and Technology Servies.2013,31(14):5-8.
[13]刘启元,李昱,陈九辉等.汶川M s 8.0地震:地壳上地幔S波速度结构的初步研究.地球物理学报,2009.52(2),309-319.Liu Q Y,Li Y,Chen J H,et al.Wenchuan M S 8.0 earthquake:preliminary study of the S-wave velocity structure of the crust and upper mantle.Chinese J.Geophys.(in Chinese),2009,52(2):309-319.
[14]吴建平,黄媛,张天中等.汶川M S 8.0级地震余震分布及周边区域P波三维速度结构研究.地球物理学报,2009,52(2):320-328.Wu J P,Huang Y,Zhang T Z,et al.Aftershock distribution of the M s 8.0Wenchuan earthquake and three dimensional P-wave velocity structure in and around source region.Chinese J.Geophys.(in Chinese),2009,52(2):320-328.
[15]雷建设,赵大鹏,苏金蓉等.龙门山断裂带地壳精细结构与汶川地震发震机理.地球物理学报,2009,52(2):339-345.Lei J S,Zhao D P,Su J R,et al.Fine seismic structure under the Longmengshan fault zone and the mechanism of large Wenchuan earthquake.Chinese J.Geophys.(in Chinese),2009,52(2):339-345.
[16]Li Z W,Ni S D,Hao T Y,et al.Uppermost mantle structure of the eastern margin of the Tibetan plateau from interstation Pn traveltime difference tomography.Earth and Planetary Science Letters,2012.335-336:195-205.
[17]钟继茂,程万正.由多个地震震源机制解求川滇地区平均应力场方向.地震学报,2006,28(4):337-346.Zhong J M,Cheng W Z.Determination of directions of the mean stress field in Sichuan-Yunnan region from a number of focal mechanism solutions.Acta Seismologica Sinica(in Chinese),2006,28(4):337-346.
[18]秦向辉,陈群策,谭成轩等.龙门山断裂带西南段现今地应力状态与地震危险性分析.岩石力学与工程学报,2013,32(增1):2870-2876.Qin X H,Chen Q C,Tan C X,et al.Analysis of current geostress state and seismic risk in southwest segment of Longmenshan fracture belt.Chinese Journal of Rock Mechanics and Engineering(in Chinese),2013,32(S1):2870-2876.
[19]万柯松,倪四道,赵里.龙门山周边地区地震波速度结构的有限频率反演.国际地震动态,2010,6:16-16.Wan K S,Ni S D,Zhao L.Finite frequency waveform inversion for velocity structure in Longmengshan area.Recent Developments in World Seismology(in Chinese),2010,6:16-16
[20]谢军,倪四道,曾祥方.四川盆地中部浅层地壳一维剪切波速度结构初步研究.四川地震,2012,143(2):20-24.Xie J,Ni S D,Zeng X F.1Dshear wave velocity structure of the shallow upper crust in central Sichuan Basin.Earthquake Research in Sichuan(in Chinese),2012,143(2):20-24.
[21]王椿镛,吴建平,楼海等.川西藏东地区的地壳P波速度结构.中国科学(D辑),2003,33(增刊):181-189.Wang C Y,Wu J P,Lou H,et al.P-wave velocity structure in western Sichuan and eastern Tibetan region.Sci.China Ser.D-Earth Sci.,2003,46(Suppl.):254-265.
[22]杨晓平,蒋溥,宋方敏等.龙门山断裂带南段错断晚更新世以来地层的证据.地震地质,1999,21(4):341-345.Yang X P,Jiang P,Song F M,et al.The evidence of the south Longmenshan fault zones cutting late Quaternary stratum.Seismology and Geology(in Chinese),1999,21(4):341-345.
[23]周永胜,何昌荣.汶川地震区的流变结构与发震高角度逆断层滑动的力学条件.地球物理学报,2009,52(2):474-484.Zhou Y C,He C R.The rhelogical structure of crust and mechanics of high-angle reverse fault slip for Wenchuan Ms8.0 earthquake.Chinese J.Geophys.(in Chinese),2009,52(2):474-484.
[24]柳畅,朱伯靖,石耀霖.粘弹性数值模拟龙门山断裂带应力积累及大震复发周期.地质学报,2012,86(1):157-169.Liu C,Zhu B J,Shi Y L.Stress accumulation of the Longmenshan Fault and recurrence interval of Wenchuan Earthquake based on viscoelasticity simulation.Acta Geologica Sinica(in Chinese),2012,86(1):157-169.
[25]单斌,熊熊,郑勇等.2008年5月12日M w 7.9汶川地震导致的周边断层应力变化.中国科学(D辑),2009,39(5):527-545.Shan B,Xiong X,Zheng Y,et al.Stress changes on major faults caused by Mw7.9Wenchuan earthquake,May12,2008.,Sci.China Ser.D-Earth Sci.,2009,52(5):593-601.601.
[26]邵志刚,周龙泉,蒋长胜等.2008年汶川M S 8.0地震对周边断层地震活动的影响.地球物理学报,2010,53(8):1784-1795.Shao Z G,Zhou L Q,Jiang C S,et al.The impact of Wenchuan M s 8.0earthquake on the seismicity of surrounding faults.Chinese J.Geophysi.(in Chinese),2010,53(8):1784-1795.
[27]石耀霖,曹建玲.库仑应力计算及应用过程中若干问题的讨论—以汶川地震为例.地球物理学报,2010,53(1):102-110.Shi Y L,Cao J L.Some aspects in static stress change calculation-case study on Wenchuan earthquake.Chinese J.Geophys.(in Chinese),2010,53(1):102-110.
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