2003年云南大姚6.2级、6.1级地震序列S波分裂研究
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摘要
在利用双差定位法对2003年7月21日、10月16日云南大姚先后发生的6.2级、6.1级地震序列进行精定位的基础上,采用互相关系数法测量了两个地震序列的快波偏振方向和快慢波的延迟时间.结果表明:①两个地震序列的S波分裂现象较明显,除三台乡台以外,大部分台站记录到的地震快波平均偏振方向与区域最大水平主压应力方向基本一致,三台乡台的偏振方向出现两个峰值,平均偏振方向是N80°E,表现出与区域最大水平主压应力方向不一致的现象;②序列延迟时间与震源深度之间没有明显规律性关系,但不同延迟时间范围内偏振方向表现出不同的规律;③两次地震序列S波分裂结果对比发现,6.2级地震序列快波的偏振方向明显较分散,快波平均偏振方向比6.1级地震序列大20°,而延迟时间方面二者相差不大;④S波分裂快波偏振方向所表现出的空间差异性,可能是由于在区域背景应力场的基础上叠加了两次6级主震产生的应力扰动引起的.
The polarization direction of fast wave and the delay time between fast and slow wave were measured for two earthquake sequences occurred continuously on 21 July (M=6.2) and 16 October (M=6.1) in Dayao, Yunnan in 2003 using cross-correlation coefficient method, after determining the high-resolution hypocentral locations of the earthquake sequences using the double-difference earthquake location algorithm. The results indicated that. ① The phenomena of S wave splitting are obvious in the two earthquake sequences, and the average polarization directions of fast wave in most stations are almost consistent with regional maximum horizontal compressive stress direction except the station Santai. There are bimodal fast directions in the polarization directions at station Santai and the mean polarization direction is N80°E, indicating an inconsistent phenomenon referred to regional maximum horizontal compressive stress direction. ② There is no apparent relation between delay time and focal depth in the sequences, but the polarization direction show different character in different delay time range. ③ The comparison of S wave splitting results in the two earthquake sequences show that the polarization direction in M=6.2 earthquake sequence is more scattered and its average fast direction is 20° larger than that of M=6.1 sequence, and the delay times between two sequences show a little difference. ④ The spatial variation in S wave splitting polarization direction may be due to the stress disturbance imposed by the two M=6 mainshocks on regional background stress field.
The polarization direction of fast wave and the delay time between fast and slow wave were measured for two earthquake sequences occurred continuously on 21 July (M=6.2) and 16 October (M=6.1) in Dayao, Yunnan in 2003 using cross-correlation coefficient method, after determining the high-resolution hypocentral locations of the earthquake sequences using the double-difference earthquake location algorithm. The results indicated that. ① The phenomena of S wave splitting are obvious in the two earthquake sequences, and the average polarization directions of fast wave in most stations are almost consistent with regional maximum horizontal compressive stress direction except the station Santai. There are bimodal fast directions in the polarization directions at station Santai and the mean polarization direction is N80°E, indicating an inconsistent phenomenon referred to regional maximum horizontal compressive stress direction. ② There is no apparent relation between delay time and focal depth in the sequences, but the polarization direction show different character in different delay time range. ③ The comparison of S wave splitting results in the two earthquake sequences show that the polarization direction in M=6.2 earthquake sequence is more scattered and its average fast direction is 20° larger than that of M=6.1 sequence, and the delay times between two sequences show a little difference. ④ The spatial variation in S wave splitting polarization direction may be due to the stress disturbance imposed by the two M=6 mainshocks on regional background stress field.
引文
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CrampinS.1978.Seismicwavepropagationthroughacrackedsolid:polarizationaspossibledilatancydiagnostic[J]GeophysJRastrSoc,53:467~496
CrampinS,VoltiT,StefanssonR.1999.Asuccessfullystress-forecastearthquake[J].GeophysJInt,138:1~5
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GephartJW.1990.FMSI:AFORTRANprogramforinvertingfault/slickensideandearthquakefocalmechanismdatatoobtaintheregionalstresstensor[J].Comput&Geosci,16(7):953~989
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MardiaKV,JuppPE.2000.DirectionalStatistics[M].HobokenNJ:JohnWiley,429
NuttliO.1961.Theeffectofearth′ssurfaceontheS-waveparticlemotion[J].BullSeismSocAmer,51:237~246
OkadaT,MatsuzawaT,MatsumotoS,etal.1994.ShearwavesplittingobservedinthesouthwesternpartofFukushi-maprefecture,northeasternJapan[J].JPhysEarth,42:303~319
OkadaY.1992.Internaldeformationduetoshearandtensilefaultsinhalf-space[J].BullSeismSocAmer,82:1018~1040
PengZ,Ben-ZionY.2004.SystematicanalysisofcrustalanisotropyalongtheKaradere-DzcebranchoftheNorthAna-tolianfault[J].GeophysJInt,159:253~274
PengZ,Ben-ZionY.2005.Spatiotemporalvariationsofcrustalanisotropyfromsimilareventsinaftershocksofthe1999M7.4IzmitandM7.1Dzce,Turkey,earthquakesequences[J].GeophysJInt,160:1~17
SavageMK,ShihXR,MeyerRP,etal.1989.Shear-waveanisotropyofactivetectonicregionsviaautomatedS-wavepolarizationanalysis[J].Tectonophysics,165:279~292
ShearerPM.1999.IntroductiontoSeismology[M].NewYork:CambridgeUniversityPress,16
ShihXR,MeyerRP.1990.Observationofshearwavesplittingfromnatureevents:SouthMoatofLongValleycaldera,California,June29toAugust12,1982[J].JGeophysRes,95:11179~11196
WyssM,BruneJN.1968.Seismicmoment,stress,andsourcedimensionsforearthquakesintheCalifornia-Nevadare-gion[J].JGeophysRes,73:4681~4694
ZhangZ,SchwartzSY.1994.SeismicanisotropyintheshallowcrustoftheLomaPrietasegmentoftheSanAndreasfaultsystem[J].JGeophysRes,99:9651~9661
陈运泰.2003.地震能量和地震效率[A].见:中国地震局监测预报司所编.地震参数数字地震学在地震预测研究中的应用[C].北京:地震出版社,51~72
丁国瑜.1991.中国岩石圈地球动力学概论[M].北京:地震出版社,1~68
高原,郑斯华.1994.唐山地区剪切波分裂研究(Ⅱ)相关函数分析法[J].中国地震,10(9):22~32
华卫,刘杰,郑斯华,等.2006.2003年云南大姚6.2级、6.1级地震序列特征分析及地震触发研究[J].中国地震,22(1):10~23
黄立人,马青,朱文耀,等.1997.高精度GPS测量得到的中国西南地区构造块体模型的初步结果[J].地震学报,19(1):22~28
赖锡安,徐菊生,卓力格图,等.2000.中国大陆主要构造块体现今运动的基本特征[J].中国地震,16(3):213~222
李白基,秦嘉政,钱晓东.2002.1995年武定6.5级地震余震的S波分裂[J].地震研究,25(2):108~114
刘堃,张中杰,胡家福,等.2001.中国陆区S波分裂的频带相关性及其意义[J].中国科学,D辑,31(2):155~161
刘祖荫,苏有锦,秦嘉政,等.2002.20世纪云南地震活动[M].北京:地震出版社,25~47
钱晓东,李白基,秦嘉政.2002.2000年云南姚安MS6.5地震余震序列S波分裂研究[J].中国地震,18(2):157~165
吴忠良.2003.地震辐射能量和震源谱[A].见:中国地震局监测预报司所编.地震参数数字地震学在地震预测研究中的应用[C].北京:地震出版社,73~81
BoothDC,CrampinS.1985.Shear-wavepolarizationsonacurvedwavefrontatanisotropicfree-surface[J].GeophysJRastrSoc,83:31~45
ChoyGL,BoatwrightJL.1995.Globalpatternsofradiatedseismicenergyandapprentstess[J].JGeophysRes,100:18205~18228
CochranES,VidaleJE,LiYG.2003.Near-faultanisotropyfollowingtheHectorMineearthquake[J].JGeophysRes,108(B9):2436~2447
CrampinS.1978.Seismicwavepropagationthroughacrackedsolid:polarizationaspossibledilatancydiagnostic[J]GeophysJRastrSoc,53:467~496
CrampinS,VoltiT,StefanssonR.1999.Asuccessfullystress-forecastearthquake[J].GeophysJInt,138:1~5
CrampinS,PeacockS,GaoY,etal.2004.Thescatteroftimedelaysinshear-wavesittingabovesmallearthquakes[J].GeophysJInt,156:39~44
DavisJC.1986.StatisticsandDataAnalysisinGeology[M].HobokenNJ:JohnWiley,646
GamarF,BernardP.1997.ShearwaveanisotropyintheErzincanbasinanditsrelationshipwithcrustalstrain[J].JGeophysRes,102:20373~20393
GephartJW.1990.FMSI:AFORTRANprogramforinvertingfault/slickensideandearthquakefocalmechanismdatatoobtaintheregionalstresstensor[J].Comput&Geosci,16(7):953~989
LearyPC,CrampinS,McEvillyTV.1990.SeismicfractureanisotropyintheEarth′scrust:Anoverview[J].JGeo-physRes,95(7):11105~11114
LiuYF,TengTL,Ben-ZionY.2004.Systematicanalysisofshear-wavesplittingintheaftershockzoneofthe1999Chi-Chi,Taiwan,earthquake:Shallowcrustalanisotropyandlackofprecursoryvariations[J].BullSeismSocAmer,94(6):2330~2347
MardiaKV,JuppPE.2000.DirectionalStatistics[M].HobokenNJ:JohnWiley,429
NuttliO.1961.Theeffectofearth′ssurfaceontheS-waveparticlemotion[J].BullSeismSocAmer,51:237~246
OkadaT,MatsuzawaT,MatsumotoS,etal.1994.ShearwavesplittingobservedinthesouthwesternpartofFukushi-maprefecture,northeasternJapan[J].JPhysEarth,42:303~319
OkadaY.1992.Internaldeformationduetoshearandtensilefaultsinhalf-space[J].BullSeismSocAmer,82:1018~1040
PengZ,Ben-ZionY.2004.SystematicanalysisofcrustalanisotropyalongtheKaradere-DzcebranchoftheNorthAna-tolianfault[J].GeophysJInt,159:253~274
PengZ,Ben-ZionY.2005.Spatiotemporalvariationsofcrustalanisotropyfromsimilareventsinaftershocksofthe1999M7.4IzmitandM7.1Dzce,Turkey,earthquakesequences[J].GeophysJInt,160:1~17
SavageMK,ShihXR,MeyerRP,etal.1989.Shear-waveanisotropyofactivetectonicregionsviaautomatedS-wavepolarizationanalysis[J].Tectonophysics,165:279~292
ShearerPM.1999.IntroductiontoSeismology[M].NewYork:CambridgeUniversityPress,16
ShihXR,MeyerRP.1990.Observationofshearwavesplittingfromnatureevents:SouthMoatofLongValleycaldera,California,June29toAugust12,1982[J].JGeophysRes,95:11179~11196
WyssM,BruneJN.1968.Seismicmoment,stress,andsourcedimensionsforearthquakesintheCalifornia-Nevadare-gion[J].JGeophysRes,73:4681~4694
ZhangZ,SchwartzSY.1994.SeismicanisotropyintheshallowcrustoftheLomaPrietasegmentoftheSanAndreasfaultsystem[J].JGeophysRes,99:9651~9661
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