2018年阿拉斯加湾M_W7.9地震震源复杂性
|
摘要
2018年1月23日,在美国阿拉斯加湾海域发生了一次MW7.9地震.震源机制解表明这次地震以走滑为主,可能发生在近东西向或南北向的陡倾角断层上,早期余震并非线型展布.我们利用视震源时间函数分析确定了此次地震的总体破裂方向,并结合余震的空间展布特征构建了相互交叉的双断层模型,进而通过联合反演远场P波和SH波数据获得了此次地震的时空破裂过程.视震源时间函数分析表明总体破裂方向既非东西也非南北,而且反演结果表明,两个断层上都发生了错动,总体破裂时间～50s,释放标量地震矩～8.11×1020 Nm.震源时间函数表现出多事件特征,且两个断层破裂的时间过程也不相同.破裂首先在南北向断层的南端开始,很快触发了东西向断层,最后终止于南北向断层的北端.每个断层都具有相当的时空复杂性,位错分布很不均匀.东西向断层具有三个凹凸体,一个位于震源附近,其他两个位于断层两端.南北向断层有两个凹凸体,均位于断层北段,最大滑动量～5.0m就出现在这里.发生最大位错的南北向断层延伸至阿拉斯加海沟,增加了触发阿拉斯加海沟其他断层发生破裂的可能性.
On January 23,2018,an MW7.9 earthquake occurred in the Gulf of Alaska,USA.As the inverted focal mechanism solution suggests,the event was mainly of strike-slip on steep faults which may run nearly from east to west or from north to south(the N-S fault and E-W fault).The early aftershocks don′t appear to be along a straight line.In this study,we determine the overall rupture direction by analyzing the apparent source time functions(ASTFs),and then,combining the direction with the pattern of the aftershocks,we build a double-fault model,with one crossing with the other,and obtain the tempo-spatial process by jointly inverting the P and SH waveform data.The analysis of the ASTFs shows that the overall rupture direction is neithernorth-to-south nor east-to-west,and the inverted results show,the two faults participate in the event,with a total duration of～50 sand a moment release of～8.11×1020 Nm.Multi-events can be recognized on the inverted source time function,and the two faults have different temporal processes.The rupture starts on southern end of the N-S fault,soon propagates on the E-W fault,and finally stops on northern end of the N-S fault.Each of the faults has quite tempospatial complexity,with highly heterogeneous slip on each of them.There are three slip asperities on the E-W fault,with one near the hypocenter while the others on two ends of the fault.There are two slip asperities on the N-S fault,with both of them on the northern end.Right here appears the maximal slip～5.0 m.The N-S fault stretches into the Gulf of Alaska,so the probability that other faults in this gulf are triggered is believed to have increased.
On January 23,2018,an MW7.9 earthquake occurred in the Gulf of Alaska,USA.As the inverted focal mechanism solution suggests,the event was mainly of strike-slip on steep faults which may run nearly from east to west or from north to south(the N-S fault and E-W fault).The early aftershocks don′t appear to be along a straight line.In this study,we determine the overall rupture direction by analyzing the apparent source time functions(ASTFs),and then,combining the direction with the pattern of the aftershocks,we build a double-fault model,with one crossing with the other,and obtain the tempo-spatial process by jointly inverting the P and SH waveform data.The analysis of the ASTFs shows that the overall rupture direction is neithernorth-to-south nor east-to-west,and the inverted results show,the two faults participate in the event,with a total duration of～50 sand a moment release of～8.11×1020 Nm.Multi-events can be recognized on the inverted source time function,and the two faults have different temporal processes.The rupture starts on southern end of the N-S fault,soon propagates on the E-W fault,and finally stops on northern end of the N-S fault.Each of the faults has quite tempospatial complexity,with highly heterogeneous slip on each of them.There are three slip asperities on the E-W fault,with one near the hypocenter while the others on two ends of the fault.There are two slip asperities on the N-S fault,with both of them on the northern end.Right here appears the maximal slip～5.0 m.The N-S fault stretches into the Gulf of Alaska,so the probability that other faults in this gulf are triggered is believed to have increased.
引文
Ammon C J,Kanamori H,Lay T,et al.2006a.The 17July 2006Java tsunami earthquake.Geophysical Research Letters,33(24):194-199,L24308,doi:10.1029/2006GL028005.
Ammon C J,Velasco A A,Lay T.2006b.Rapid estimation of firstorder rupture characteristics for large earthquakes using surface waves:2004Sumatra-Andaman earthquake.Geophysical Research Letters,33(14):L14314,doi:10.1029/2006GL026303.
Antolik M,Dreger D S.2003.Rupture process of the 26January2001 MW7.6Bhuj,India,Earthquake from teleseismic broadband data.Bulletin of the Seismological Society of America,93(3):1235-1248.
Avouac J P,Meng L S,Wei S J,et al.2015.Lower edge of locked Main Himalayan Thrust unzipped by the 2015Gorkha earthquake.Nature Geoscience,8(9):708-711.
Bertero M,Bindi D,Boccacci P,et al.1997.Application of the projected Landweber method to the estimation of the source time function in seismology.Inverse Problems,13(2):465-486.
Bird P.2003.An updated digital model of plate boundaries.Geochemistry,Geophysics,Geosystems,4(3):1027,doi:10.1029/2001GC000252.
Chen Y T,Zhou J Y,Ni J C.1991.Inversion of near-sourcebroadband accelerograms for the earthquake source-time function.Tectonophysics,197(1):89-98.
DeMets C,Gordon R G,Argus D F.2010.Geologically current plate motions.GeophysicalJournalInternational,181(1):1-80.
Dreger D S.1994.Investigation of the rupture process of the 28June 1992Landers earthquake utilizing TERRAscope.Bulletin of the Seismological Society of America,84(3):713-724.
Ekstr9m G,Nettles M,Dziewoński A M.2012.The global CMTproject 2004-2010:Centroid-moment tensors for 13,017eartquakes.Physics of the Earth and Planetary Interiors,200-201:1-9.
Galetzka J,Melgar D,Genrich J F,et al.2015.Slip pulse and resonance of the Kathmandu basin during the 2015 Gorkha earthquake,Nepal.Science,349(6252):1091-1095.
Gusman A R,Murotani S,Satake K,et al.2015.Fault slip distribution of the 2014Iquique,Chile,earthquake estimated from ocean-wide tsunami waveforms and GPS data.Geophysical Research Letters,42(4):1053-1060.
Hartzell S H,Heaton T H.1983.Inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979Imperial Valley,California,earthquake.Bulletin of the Seismological Society of America,73(6A):1553-1583.
Helmberger D,Wiggins R A.1971.Upper mantle structure of midwestern United States.Journal of Geophysical Research,76(14):3229-3245.
Kennett B L N,Engdahl E R,Buland R.1995.Constraints on seismic velocities in the Earth from traveltimes.Geophysical Journal International,122(1):108-124.
Krabbenhoeft A,von Huene R,Miller J J,et al.2018.Strike-slip23January 2018 MW7.9Gulf of Alaska rare intraplate earthquake:Complex rupture of a fracture zone system.Scientific Reports,8:13706,doi:10.1038/s41598-018-32071-4.
Kraeva N.2004.Tikhonov's regularization for deconvolution in the empirical Green function method and vertical directivity effect.Tectonophysics,383(1-2):29-44.
Lanza V,Spallarossa D,Cattaneo M,et al.1999.Source parameters of small events using constrained deconvolution with empirical Green′s functions.Geophysical Journal International,137(3):651-662.
Lay T,Wallace T C.1995.Modern Global Seismology.San Diego:Academic Press.
Lay T,Kanamori H,Ammon C J,et al.2009.The 2006-2007Kuril Islands great earthquake sequence.Journal of Geophysical Research:Solid Earth,114(B11):B11308,doi:10.1029/2008JB006280.
Lay T,Ammon C J,Kanamori H,et al.2010.The 2009SamoaTonga great earthquake triggered doublet.Nature,466(7309):964-968.
Lay T,Ye L L,Ammon C J,et al.2017.Intraslab rupture triggering megathrust rupture coseismically in the 17December2016Solomon Islands MW7.9earthquake.Geophysical Research Letters,44(3):1286-1292.
Lay T,Ye L L,Bai Y F,et al.2018.The 2018 MW7.9Gulf of Alaska earthquake:Multiple fault rupture in the Pacific plate.Geophysical Research Letters,45(18):9542-9551.
Montagner J P,Kennett B L N.1996.How to reconcile body-wave and normal-mode reference earth models.Geophysical Journal International,125(1):229-248.
Park S,Ishii M.2015.Inversion for rupture properties based upon3-D directivity effect and application to deep earthquakes in the Sea of Okhotsk region.Geophysical Journal International,203(2):1011-1025.
Piana M,Bertero M.1997.Projected Landweber method and preconditioning.Inverse Problems,13(2):441-463.
Ruppert N A,Rollins C,Zhang A,et al.2018.Complex faulting and triggered rupture during the 2018 MW7.9offshore Kodiak,Alaska,earthquake.Geophysical Research Letters,45(15):7533-7541.
Sandwell D T,Müller R D,Smith W H F,et al.2014.New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure.Science,346(6205):65-67.
Simons M,Minson S E,Sladen A,et al.2011.The 2011magnitude9.0Tohoku-Oki earthquake:mosaicking the megathrust from seconds to centuries.Science,332(6036):1421-1425.
Vallée M.2004.Stabilizing the empirical Green function analysis:development of the projected Landweber method.Bulletin of the Seismological Society of America,94(2):394-409.
Wang R J.1999.A simple orthonormalization method for stable and efficient computation of Green′s functions.Bulletin of the Seismological Society of America,89(3):733-741.
Xu L S,Zhang X,Yan C,et al.2014.Analysis of the Love waves for the source complexity of the Ludian MS6.5earthquake.Chinese J.Geophys.(in Chinese),57(9):3006-3017,doi:10.6038/cjg20140925.
Yagi Y,Mikumo T,Pacheco J,et al.2004.Source rupture process of the Tecomán,Colima,Mexico Earthquake of 22January2003,determined by joint inversion of teleseismic body-wave and near-source data.Bulletin of the Seismological Society of America,94(5):1795-1807.
Yue H,Lay T,Koper K D.2012.Enéchelon and orthogonal fault ruptures of the 11 April 2012great intraplate earthquakes.Nature,490(7419):245-249.
Zhang X,Xu L S.2015.Inversion of the apparent source time functions for the rupture process of the Nepal MS8.1earthquake.Chinese J.Geophys.(in Chinese),58(6):1881-1890,doi:10.6038/cjg20150604.
Zhang X.2016.Study on new methods for analysis of the complexity of source rupture process based on apparent source time functions[Ph.D.thesis](in Chinese).Beijing:Institute of Geophysics,China Earthquake Administration.
Zhang X,Yan C,Xu L S.2016.Analysis of the Love-waves for the rupture processes of the 2014earthquake-doublet of Kangding,Sichuan.Chinese J.Geophys.(in Chinese),59(7):2453-2467,doi:10.6038/cjg20160712.
Zhang Y,Xu L S,Chen Y T.2009.PLD method for retrieving apparent source time function and its application to the 2005Kashmir MW7.6earthquake.Chinese J.Geophys.(in Chinese),52(3):672-680.
Zhang Y,Feng W P,Chen Y T,et al.2012.The 2009L′Aquila MW6.3earthquake:a new technique to locate the hypocentre in the joint inversion of earthquake rupture process.Geophysical Journal International,191(3):1417-1426.
许力生,张旭,严川等.2014.基于勒夫波的鲁甸MS6.5地震震源复杂性分析.球物理学报,57(9):3006-3017,doi:10.6038/cjg20140925.
张旭,许力生.2015.利用视震源时间函数反演尼泊尔MS8.1地震破裂过程.地球物理学报,58(6):1881-1890,doi:10.6038/cjg20150604.
张旭.2016.基于视震源时间函数的震源过程复杂性分析新方法研究[博士论文].北京:中国地震局地球物理研究所.
张旭,严川,许力生.2016.2014年四川康定双震震源的勒夫波分析.地球物理学报,59(7):2453-2467,doi:10.6038/cjg20160712.
张勇,许力生,陈运泰.2009.提取视震源时间函数的PLD方法及其对2005年克什米尔MW7.6地震的应用.地球物理学报,52(3):672-680.
Ammon C J,Velasco A A,Lay T.2006b.Rapid estimation of firstorder rupture characteristics for large earthquakes using surface waves:2004Sumatra-Andaman earthquake.Geophysical Research Letters,33(14):L14314,doi:10.1029/2006GL026303.
Antolik M,Dreger D S.2003.Rupture process of the 26January2001 MW7.6Bhuj,India,Earthquake from teleseismic broadband data.Bulletin of the Seismological Society of America,93(3):1235-1248.
Avouac J P,Meng L S,Wei S J,et al.2015.Lower edge of locked Main Himalayan Thrust unzipped by the 2015Gorkha earthquake.Nature Geoscience,8(9):708-711.
Bertero M,Bindi D,Boccacci P,et al.1997.Application of the projected Landweber method to the estimation of the source time function in seismology.Inverse Problems,13(2):465-486.
Bird P.2003.An updated digital model of plate boundaries.Geochemistry,Geophysics,Geosystems,4(3):1027,doi:10.1029/2001GC000252.
Chen Y T,Zhou J Y,Ni J C.1991.Inversion of near-sourcebroadband accelerograms for the earthquake source-time function.Tectonophysics,197(1):89-98.
DeMets C,Gordon R G,Argus D F.2010.Geologically current plate motions.GeophysicalJournalInternational,181(1):1-80.
Dreger D S.1994.Investigation of the rupture process of the 28June 1992Landers earthquake utilizing TERRAscope.Bulletin of the Seismological Society of America,84(3):713-724.
Ekstr9m G,Nettles M,Dziewoński A M.2012.The global CMTproject 2004-2010:Centroid-moment tensors for 13,017eartquakes.Physics of the Earth and Planetary Interiors,200-201:1-9.
Galetzka J,Melgar D,Genrich J F,et al.2015.Slip pulse and resonance of the Kathmandu basin during the 2015 Gorkha earthquake,Nepal.Science,349(6252):1091-1095.
Gusman A R,Murotani S,Satake K,et al.2015.Fault slip distribution of the 2014Iquique,Chile,earthquake estimated from ocean-wide tsunami waveforms and GPS data.Geophysical Research Letters,42(4):1053-1060.
Hartzell S H,Heaton T H.1983.Inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979Imperial Valley,California,earthquake.Bulletin of the Seismological Society of America,73(6A):1553-1583.
Helmberger D,Wiggins R A.1971.Upper mantle structure of midwestern United States.Journal of Geophysical Research,76(14):3229-3245.
Kennett B L N,Engdahl E R,Buland R.1995.Constraints on seismic velocities in the Earth from traveltimes.Geophysical Journal International,122(1):108-124.
Krabbenhoeft A,von Huene R,Miller J J,et al.2018.Strike-slip23January 2018 MW7.9Gulf of Alaska rare intraplate earthquake:Complex rupture of a fracture zone system.Scientific Reports,8:13706,doi:10.1038/s41598-018-32071-4.
Kraeva N.2004.Tikhonov's regularization for deconvolution in the empirical Green function method and vertical directivity effect.Tectonophysics,383(1-2):29-44.
Lanza V,Spallarossa D,Cattaneo M,et al.1999.Source parameters of small events using constrained deconvolution with empirical Green′s functions.Geophysical Journal International,137(3):651-662.
Lay T,Wallace T C.1995.Modern Global Seismology.San Diego:Academic Press.
Lay T,Kanamori H,Ammon C J,et al.2009.The 2006-2007Kuril Islands great earthquake sequence.Journal of Geophysical Research:Solid Earth,114(B11):B11308,doi:10.1029/2008JB006280.
Lay T,Ammon C J,Kanamori H,et al.2010.The 2009SamoaTonga great earthquake triggered doublet.Nature,466(7309):964-968.
Lay T,Ye L L,Ammon C J,et al.2017.Intraslab rupture triggering megathrust rupture coseismically in the 17December2016Solomon Islands MW7.9earthquake.Geophysical Research Letters,44(3):1286-1292.
Lay T,Ye L L,Bai Y F,et al.2018.The 2018 MW7.9Gulf of Alaska earthquake:Multiple fault rupture in the Pacific plate.Geophysical Research Letters,45(18):9542-9551.
Montagner J P,Kennett B L N.1996.How to reconcile body-wave and normal-mode reference earth models.Geophysical Journal International,125(1):229-248.
Park S,Ishii M.2015.Inversion for rupture properties based upon3-D directivity effect and application to deep earthquakes in the Sea of Okhotsk region.Geophysical Journal International,203(2):1011-1025.
Piana M,Bertero M.1997.Projected Landweber method and preconditioning.Inverse Problems,13(2):441-463.
Ruppert N A,Rollins C,Zhang A,et al.2018.Complex faulting and triggered rupture during the 2018 MW7.9offshore Kodiak,Alaska,earthquake.Geophysical Research Letters,45(15):7533-7541.
Sandwell D T,Müller R D,Smith W H F,et al.2014.New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure.Science,346(6205):65-67.
Simons M,Minson S E,Sladen A,et al.2011.The 2011magnitude9.0Tohoku-Oki earthquake:mosaicking the megathrust from seconds to centuries.Science,332(6036):1421-1425.
Vallée M.2004.Stabilizing the empirical Green function analysis:development of the projected Landweber method.Bulletin of the Seismological Society of America,94(2):394-409.
Wang R J.1999.A simple orthonormalization method for stable and efficient computation of Green′s functions.Bulletin of the Seismological Society of America,89(3):733-741.
Xu L S,Zhang X,Yan C,et al.2014.Analysis of the Love waves for the source complexity of the Ludian MS6.5earthquake.Chinese J.Geophys.(in Chinese),57(9):3006-3017,doi:10.6038/cjg20140925.
Yagi Y,Mikumo T,Pacheco J,et al.2004.Source rupture process of the Tecomán,Colima,Mexico Earthquake of 22January2003,determined by joint inversion of teleseismic body-wave and near-source data.Bulletin of the Seismological Society of America,94(5):1795-1807.
Yue H,Lay T,Koper K D.2012.Enéchelon and orthogonal fault ruptures of the 11 April 2012great intraplate earthquakes.Nature,490(7419):245-249.
Zhang X,Xu L S.2015.Inversion of the apparent source time functions for the rupture process of the Nepal MS8.1earthquake.Chinese J.Geophys.(in Chinese),58(6):1881-1890,doi:10.6038/cjg20150604.
Zhang X.2016.Study on new methods for analysis of the complexity of source rupture process based on apparent source time functions[Ph.D.thesis](in Chinese).Beijing:Institute of Geophysics,China Earthquake Administration.
Zhang X,Yan C,Xu L S.2016.Analysis of the Love-waves for the rupture processes of the 2014earthquake-doublet of Kangding,Sichuan.Chinese J.Geophys.(in Chinese),59(7):2453-2467,doi:10.6038/cjg20160712.
Zhang Y,Xu L S,Chen Y T.2009.PLD method for retrieving apparent source time function and its application to the 2005Kashmir MW7.6earthquake.Chinese J.Geophys.(in Chinese),52(3):672-680.
Zhang Y,Feng W P,Chen Y T,et al.2012.The 2009L′Aquila MW6.3earthquake:a new technique to locate the hypocentre in the joint inversion of earthquake rupture process.Geophysical Journal International,191(3):1417-1426.
许力生,张旭,严川等.2014.基于勒夫波的鲁甸MS6.5地震震源复杂性分析.球物理学报,57(9):3006-3017,doi:10.6038/cjg20140925.
张旭,许力生.2015.利用视震源时间函数反演尼泊尔MS8.1地震破裂过程.地球物理学报,58(6):1881-1890,doi:10.6038/cjg20150604.
张旭.2016.基于视震源时间函数的震源过程复杂性分析新方法研究[博士论文].北京:中国地震局地球物理研究所.
张旭,严川,许力生.2016.2014年四川康定双震震源的勒夫波分析.地球物理学报,59(7):2453-2467,doi:10.6038/cjg20160712.
张勇,许力生,陈运泰.2009.提取视震源时间函数的PLD方法及其对2005年克什米尔MW7.6地震的应用.地球物理学报,52(3):672-680.
© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号 地址：北京市海淀区学院路29号 邮编：100083 电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700 |