基于InSAR同震形变观测反演2010年新西兰南岛M_w7.1 Darfield地震同震破裂分布
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摘要
2010年9月4日新西兰南岛Canterbury平原发生了Mw7.1地震,震源深度约为10km.本次地震发生在一条震前不为人所知的断层上.我们利用覆盖整个震区的合成孔径雷达(SAR)观测资料,通过干涉处理分析获得雷达视线向(LOS)同震形变场;以此资料为约束反演了断层的几何参数以及同震破裂分布.结果显示,该地震造成四条相对独立断层的破裂.大部分的地震矩释放发生在Greendale断层(编号1—4),其错动以右旋走滑为主,最大破裂约为8.5m.其它三条断层中,经过震源的逆冲断层最大破裂为5.1m(编号6),位于Greendale断层以西的逆冲断层最大破裂为3.5m(编号5),位于Greendale断层北面的走滑断层最大破裂为1.9m(编号7).反演的Greendale断层地表滑动与地质调查得到的地表破裂在形态和数值上均吻合较好.本次地震释放的地震矩为5.0×1019 N.m,矩震级为7.1.板块边界带形变场分析表明,Darfield地震的发生受边界带应变分配在该地区残留构造应力场控制,其复杂性体现了区域构造应力场的特点.地震对其周围地区的应力场影响较大,库仑应力增加区与余震分布有一定对应关系,并在2011年Christchurch 6.3级地震发震断层区域造成约0.1bar的库仑应力增加,对此地震有一定的触发作用.
The 2010 Darfield Mw7.1 earthquake occurred on a previously unknown fault zone,which absorbs only a minor portion of relative plate motion between the Pacific and Australia plates there.We attempt to obtain detailed information about fault geometry and rupture distribution of this event using InSAR data.Combining geological field survey observations with SAR displacement fringes,correlation,and range and azimuth offsets,we identify four faults which slipped during co-seismic rupture,of which seven segments are distinguished with various strikes and dip angles.Our inversion results show that the slip is concentrated in the upper 10 km depth.Slips along the Greendale fault(including four segments) are predominantly dextral with a maximum up to 8.5 m.The fault coinciding with the earthquake hypocenter slipped reversely up to ~5.1 m.The third fault located west of the Greendale fault also reversely ruptured,with a peak of ~3.5 m.Slip on the fourth fault located north of the Greendale fault and east of the second fault is minor,no more than 1.9 m.We also compare the top 1 km slip along the Greendale fault with surface rupture distribution,and find very good agreement between the two.The maximum surface slip is about 6 m,located about 26 km east of the west end of the fault surface rupture.The total seismic moment release is 5.0×1019N·m,equivalent to an Mw=7.12 event.Main features of InSAR data are well recovered,the residuals near the epicenter are less than 20 cm,confirming good data fitting of our fault slip model.Based on this fault slip model we calculate about 1 bar of Coulomb stress change at the hypocenter of the 2011 Mw6.3 Christchurch earthquake,located about 30 km east of the Darfield earthquake.
The 2010 Darfield Mw7.1 earthquake occurred on a previously unknown fault zone,which absorbs only a minor portion of relative plate motion between the Pacific and Australia plates there.We attempt to obtain detailed information about fault geometry and rupture distribution of this event using InSAR data.Combining geological field survey observations with SAR displacement fringes,correlation,and range and azimuth offsets,we identify four faults which slipped during co-seismic rupture,of which seven segments are distinguished with various strikes and dip angles.Our inversion results show that the slip is concentrated in the upper 10 km depth.Slips along the Greendale fault(including four segments) are predominantly dextral with a maximum up to 8.5 m.The fault coinciding with the earthquake hypocenter slipped reversely up to ~5.1 m.The third fault located west of the Greendale fault also reversely ruptured,with a peak of ~3.5 m.Slip on the fourth fault located north of the Greendale fault and east of the second fault is minor,no more than 1.9 m.We also compare the top 1 km slip along the Greendale fault with surface rupture distribution,and find very good agreement between the two.The maximum surface slip is about 6 m,located about 26 km east of the west end of the fault surface rupture.The total seismic moment release is 5.0×1019N·m,equivalent to an Mw=7.12 event.Main features of InSAR data are well recovered,the residuals near the epicenter are less than 20 cm,confirming good data fitting of our fault slip model.Based on this fault slip model we calculate about 1 bar of Coulomb stress change at the hypocenter of the 2011 Mw6.3 Christchurch earthquake,located about 30 km east of the Darfield earthquake.
引文
[1]Gledhill K,Ristau J,Reyners M,et al.The darfield(Canterbury,New Zealand)Mw7.1earthquake of september2010:a preliminary seismological report.SeismologicalResearch Letters,2011,82(3):378-386,doi:10.1785/gssrl.82.6.378.
[2]Reyners M.Lessons from the destructive Mw6.3Christchurch,New Zealand,earthquake.Seismol.Res.Lett.,2011,82(3):371-372.
[3]Norris R J,Cooper A F.Late quaternary slip rates and slippartitioning on the alpine fault,New Zealand.J.StructuralGeol.,2001,23(2-3):507-520.
[4]Beavan J,Samsonov S,Motagh M,et al.The MW7.1Darfield(CANTERBURY)earthquake:Geodetic observationsand preliminary source model.Bull.N.Z.Soc.Earthq.Eng,2010,43:228-235.
[5]Wallace L M,Beavan J.A large slow slip event on thecentral Hikurangi subduction interface beneath the Manawaturegion,North Island,New Zealand.Geophysical ResearchLetters,2006,33(11),doi:10.1029/2006GL026009.
[6]Wallace L M,Beavan J,McCaffrey R,et al.Balancing theplate motion budget in the South Island,New Zealand usingGPS,geological and seismological data.Geophysical JournalInternational,2007,168(1):332-352.
[7]USGS http://earthquake.usgs.gov/earthquakes/eqinthenews/2010/us2010atbj/
[8]Quigley M,Dissen R V,Villamor P,et al.Surface ruptureof the greendale fault during the darfield(canterbury)earthquake,New Zealand:initial findings.Bulletin of theNew Zealand Society for Earthquake Engineering,2010,43(4):236-242.
[9]Holden C,Beavan J,Fry B,et al.Preliminary source modelof the Mw7.1Darfield earthquake from geological,geodeticand seismic data//Proceedings of the Ninth PacificConference on Earthquake Engineering Building an Earthquake-Resilient Society,Auckland,New Zealand,2011.
[10]Elliott J R,Nissen E K,England P C,et al.Slip in the2010—2011Canterbury earthquakes,New Zealand.Journalof Geophysical Research,2012,117,doi:10.1029/2011JB008868.
[11]Delouis B,Giardini D,Lundgren P,et al.Joint inversion ofInSAR,GPS,Teleseismic,and Strong-Motion data for thespatial and temporal distribution of earthquake slip:Application to the 1999izmit mainshock.Bulletin of theSeismological Society of America,2002,92(1):278-299.
[12]Delouis B,Nocquet J M,Vallée M,et al.Slip distribution ofthe February 27,2010 Mw=8.8maule earthquake,centralchile,from static and high-rate GPS,InSAR,and broadbandteleseismic data.Geophysical Research Letters,2010,37(17),L17305,doi:10.1029/2010GL043899.
[13]Rosen P A,Hensley S,Peltzer G,et al.Updated repeatorbit interferometry package released.Eos,TransactionsAmerican Geophysical Union,2004,85(5):47.
[14]Fialko Y,Simons M,Agnew D.The complete(3-D)surfacedisplacement field in the epicentral area of the 1999 Mw7.1Hector Mine Earthquake,California,from space geodeticobservations.Geophysical Research Letters,2001,28(16):3063-3066.
[15]Farr T G,Rosen P A,Caro E,et al.The shuttle radartopography mission.Rev.Geophys.,2007,45(2),doi:10.1029/2005RG000183.
[16]Hanssen R F.Radar Interferometry-Data Interpretation andError Analysis(V.2).Dordrecht:Kluwer Academic Pub.,2001.
[17]孙建宝,徐锡伟,石耀霖等.东昆仑断裂玛尼段震间形变场的InSAR观测及断层滑动率初步估计.自然科学进展,2007,17(10):1361-1370.Sun J B,Xu X W,Shi Y L,et al.InSAR observation of theinter-seismic deformation of Mani segment in the East Kunlunfault and estimation of the slip rate.Progress in NaturalScience(in Chinese),2007,17(10):1361-1370.
[18]Fukuda J,Johnson K M.A fully Bayesian inversion forspatial distribution of fault slip with objective smoothing.Bulletin of the Seismological Society of America,2008,98(3):1128-1146.
[19]Fukuda J,Johnson K M.Mixed linear-non-linear inversion ofcrustal deformation data:Bayesian inference of model,weighting and regularization parameters.GeophysicalJournal International,2010,181(3):1441-1458.
[20]Okada Y.Internal deformation due to shear and tensile faultsin a half-space,Bull.Seism.Soc.Am.,1992,82(2):1018-1040.
[21]Sun J B,Shen Z K,Bürgmann R,et al.A three-stepMaximum-A-Posteriori probability method for INSAR datainversion of coseismic rupture with application to the April14,2010 Mw6.9 Yushu,China earthquake.Journal ofGeophysical Research:Solid Earth,doi:10.1002/jgrb.50244.
[22]Ingber L.Simulated annealing:Practice versus theory.Math.Comput.Model.,1993,18(11):29-57.
[23]Quigley M,van Dissen R,Litchfield N,et al.Surfacerupture during the 2010 Mw7.1 Darfield(Canterbury)earthquake:Implications for fault rupture dynamics andseismic-hazard analysis.Geology,2012,40(1):55-58.
[24]GeoNet http://www.geonet.org.nz/
[25]Jónsson S,Zebker H,Segall P,et al.Fault slip distributionof the 1999 Mw7.1 Hector Mine,California,earthquake,estimated from satellite radar and GPS measurements.Bulletin of the Seismological Society of America,2002,92(4):1377-1389.
[26]孙建宝,徐锡伟,沈正康等.基于线弹性位错模型及干涉雷达同震形变场反演1997年玛尼Mw7.5级地震参数—I.均匀滑动反演.地球物理学报,2007,50(4):1097-1110.Sun J B,Xu X W,Shen Z K,et al.Parameter inversion ofthe 1997 Mani earthquake from INSAR co-seismicdeformation field based on linear elastic dislocation model—Ⅰ.uniform slip inversion.Chinese J.Geophys.(in Chinese),2007,50(4):1097-1110.
[27]King G C P,Stein R S,Lin J.Static stress changes and thetriggering of earthquakes.Bulletin of the SeismologicalSociety of America,1994,84(3):935-953.
[28]Lin J,Stein R S.Stress triggering in thrust and subductionearthquakes and stress interaction between the southern SanAndreas and nearby thrust and strike-slip faults.Journal ofGeophysical Research,2004,109(B2),doi:10.1029/2003JB002607.
[29]Sella G F,Dixon T H,Mao A L.REVEL:A model forrecent plate velocities from space geodesy.Journal ofGeophysical Research,2002,107(B4),doi:10.1029/2000JB000033.
[2]Reyners M.Lessons from the destructive Mw6.3Christchurch,New Zealand,earthquake.Seismol.Res.Lett.,2011,82(3):371-372.
[3]Norris R J,Cooper A F.Late quaternary slip rates and slippartitioning on the alpine fault,New Zealand.J.StructuralGeol.,2001,23(2-3):507-520.
[4]Beavan J,Samsonov S,Motagh M,et al.The MW7.1Darfield(CANTERBURY)earthquake:Geodetic observationsand preliminary source model.Bull.N.Z.Soc.Earthq.Eng,2010,43:228-235.
[5]Wallace L M,Beavan J.A large slow slip event on thecentral Hikurangi subduction interface beneath the Manawaturegion,North Island,New Zealand.Geophysical ResearchLetters,2006,33(11),doi:10.1029/2006GL026009.
[6]Wallace L M,Beavan J,McCaffrey R,et al.Balancing theplate motion budget in the South Island,New Zealand usingGPS,geological and seismological data.Geophysical JournalInternational,2007,168(1):332-352.
[7]USGS http://earthquake.usgs.gov/earthquakes/eqinthenews/2010/us2010atbj/
[8]Quigley M,Dissen R V,Villamor P,et al.Surface ruptureof the greendale fault during the darfield(canterbury)earthquake,New Zealand:initial findings.Bulletin of theNew Zealand Society for Earthquake Engineering,2010,43(4):236-242.
[9]Holden C,Beavan J,Fry B,et al.Preliminary source modelof the Mw7.1Darfield earthquake from geological,geodeticand seismic data//Proceedings of the Ninth PacificConference on Earthquake Engineering Building an Earthquake-Resilient Society,Auckland,New Zealand,2011.
[10]Elliott J R,Nissen E K,England P C,et al.Slip in the2010—2011Canterbury earthquakes,New Zealand.Journalof Geophysical Research,2012,117,doi:10.1029/2011JB008868.
[11]Delouis B,Giardini D,Lundgren P,et al.Joint inversion ofInSAR,GPS,Teleseismic,and Strong-Motion data for thespatial and temporal distribution of earthquake slip:Application to the 1999izmit mainshock.Bulletin of theSeismological Society of America,2002,92(1):278-299.
[12]Delouis B,Nocquet J M,Vallée M,et al.Slip distribution ofthe February 27,2010 Mw=8.8maule earthquake,centralchile,from static and high-rate GPS,InSAR,and broadbandteleseismic data.Geophysical Research Letters,2010,37(17),L17305,doi:10.1029/2010GL043899.
[13]Rosen P A,Hensley S,Peltzer G,et al.Updated repeatorbit interferometry package released.Eos,TransactionsAmerican Geophysical Union,2004,85(5):47.
[14]Fialko Y,Simons M,Agnew D.The complete(3-D)surfacedisplacement field in the epicentral area of the 1999 Mw7.1Hector Mine Earthquake,California,from space geodeticobservations.Geophysical Research Letters,2001,28(16):3063-3066.
[15]Farr T G,Rosen P A,Caro E,et al.The shuttle radartopography mission.Rev.Geophys.,2007,45(2),doi:10.1029/2005RG000183.
[16]Hanssen R F.Radar Interferometry-Data Interpretation andError Analysis(V.2).Dordrecht:Kluwer Academic Pub.,2001.
[17]孙建宝,徐锡伟,石耀霖等.东昆仑断裂玛尼段震间形变场的InSAR观测及断层滑动率初步估计.自然科学进展,2007,17(10):1361-1370.Sun J B,Xu X W,Shi Y L,et al.InSAR observation of theinter-seismic deformation of Mani segment in the East Kunlunfault and estimation of the slip rate.Progress in NaturalScience(in Chinese),2007,17(10):1361-1370.
[18]Fukuda J,Johnson K M.A fully Bayesian inversion forspatial distribution of fault slip with objective smoothing.Bulletin of the Seismological Society of America,2008,98(3):1128-1146.
[19]Fukuda J,Johnson K M.Mixed linear-non-linear inversion ofcrustal deformation data:Bayesian inference of model,weighting and regularization parameters.GeophysicalJournal International,2010,181(3):1441-1458.
[20]Okada Y.Internal deformation due to shear and tensile faultsin a half-space,Bull.Seism.Soc.Am.,1992,82(2):1018-1040.
[21]Sun J B,Shen Z K,Bürgmann R,et al.A three-stepMaximum-A-Posteriori probability method for INSAR datainversion of coseismic rupture with application to the April14,2010 Mw6.9 Yushu,China earthquake.Journal ofGeophysical Research:Solid Earth,doi:10.1002/jgrb.50244.
[22]Ingber L.Simulated annealing:Practice versus theory.Math.Comput.Model.,1993,18(11):29-57.
[23]Quigley M,van Dissen R,Litchfield N,et al.Surfacerupture during the 2010 Mw7.1 Darfield(Canterbury)earthquake:Implications for fault rupture dynamics andseismic-hazard analysis.Geology,2012,40(1):55-58.
[24]GeoNet http://www.geonet.org.nz/
[25]Jónsson S,Zebker H,Segall P,et al.Fault slip distributionof the 1999 Mw7.1 Hector Mine,California,earthquake,estimated from satellite radar and GPS measurements.Bulletin of the Seismological Society of America,2002,92(4):1377-1389.
[26]孙建宝,徐锡伟,沈正康等.基于线弹性位错模型及干涉雷达同震形变场反演1997年玛尼Mw7.5级地震参数—I.均匀滑动反演.地球物理学报,2007,50(4):1097-1110.Sun J B,Xu X W,Shen Z K,et al.Parameter inversion ofthe 1997 Mani earthquake from INSAR co-seismicdeformation field based on linear elastic dislocation model—Ⅰ.uniform slip inversion.Chinese J.Geophys.(in Chinese),2007,50(4):1097-1110.
[27]King G C P,Stein R S,Lin J.Static stress changes and thetriggering of earthquakes.Bulletin of the SeismologicalSociety of America,1994,84(3):935-953.
[28]Lin J,Stein R S.Stress triggering in thrust and subductionearthquakes and stress interaction between the southern SanAndreas and nearby thrust and strike-slip faults.Journal ofGeophysical Research,2004,109(B2),doi:10.1029/2003JB002607.
[29]Sella G F,Dixon T H,Mao A L.REVEL:A model forrecent plate velocities from space geodesy.Journal ofGeophysical Research,2002,107(B4),doi:10.1029/2000JB000033.
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