由地震分布丛集性给出断层参数的一种新方法
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摘要
由于大范围内地质构造的复杂性和介质的非均匀性,发震断层面的几何形态一般十分复杂.如果大地震的破裂过程涉及多个断层的活动,则发震断层并非是单一断层平面,而是多个断层面的组合.利用地震空间位置分布丛集性,即震源点成丛位于断层面附近的假设,结合稳健扩充算法和主成分分析给出一种可以重构活断层网络三维空间结构的新方法.该方法每次从震源点集中处开始,利用假设检验扩充子断层面,并得到多个子断层面.接着按震源点属于最近断层面的准则把各子断层面内的震源点进行竞争,并根据一定假设合并和删除一些子断层面,最后用主成分分析确定每个子断层面参数.于是可根据地震事件目录给出一组矩形区域来描述断层面网络结构,其中每个矩形断层面由其位置、走向和倾角确定.通过计算机模拟发现,新方法可成功地重建模拟地震目录的断层面,最后用于南加州1992年6月28日发生的Landers地震部分余震目录中,得到各个子断层面参数与已知地质破裂或隐伏断层相当一致.
Because of the complex characteristics of the tectonic systems and medium heterogeneity in a wide region,the geometric shape of faults is usually complicated.If a major earthquake takes place,multiple faults are involved.And thus the fault planes are not a single fault plane but combined by several faults.We propose a new method that is able to reconstruct the three-dimensional structure of the active part of a fault network using the spatial location of earthquakes.Every time,the cluster consisting of neighboring several seismic events is selected randomly from the seismic events,and is gradually expanded by hypothesis testing,thus several clusters can be extracted.Subsequently,according to the criteria that any event point should be assigned to nearest cluster,the seismic events in extracted clusters are reassigned to different clusters.Some clusters are deleted or merged if they are too small or too close.Based on the remaining seismic event clusters,the parameters of fault planes are determined by the principal component analysis.So,given a catalog of seismic events,according to above procedure,we can find a series of rectangular-shaped fault planes which is characterized by its location,strike angle and dip angle to describe the spatial rupture structure of a large earthquake.The simulation results show that the algorithm successfully reconstructs the fault segments of synthetic earthquake catalogs.Applied to the real catalog constituted of a subset of the aftershock sequence of the 28 June 1992 Landers earthquake in southern California,the reconstructed plane segments fully agree with faults already known on geological maps or with blind faults.
Because of the complex characteristics of the tectonic systems and medium heterogeneity in a wide region,the geometric shape of faults is usually complicated.If a major earthquake takes place,multiple faults are involved.And thus the fault planes are not a single fault plane but combined by several faults.We propose a new method that is able to reconstruct the three-dimensional structure of the active part of a fault network using the spatial location of earthquakes.Every time,the cluster consisting of neighboring several seismic events is selected randomly from the seismic events,and is gradually expanded by hypothesis testing,thus several clusters can be extracted.Subsequently,according to the criteria that any event point should be assigned to nearest cluster,the seismic events in extracted clusters are reassigned to different clusters.Some clusters are deleted or merged if they are too small or too close.Based on the remaining seismic event clusters,the parameters of fault planes are determined by the principal component analysis.So,given a catalog of seismic events,according to above procedure,we can find a series of rectangular-shaped fault planes which is characterized by its location,strike angle and dip angle to describe the spatial rupture structure of a large earthquake.The simulation results show that the algorithm successfully reconstructs the fault segments of synthetic earthquake catalogs.Applied to the real catalog constituted of a subset of the aftershock sequence of the 28 June 1992 Landers earthquake in southern California,the reconstructed plane segments fully agree with faults already known on geological maps or with blind faults.
引文
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[13]朱艾斓,徐锡伟,胡平等.首都圈地区小震重新定位及其在地震构造研究中的应用.地质评论,2005,51(3):268-274.Zhu A L,Xu X W,Hu P,et al.Relocation of smallearthquakes in Beijing area and its implication toseismotectonics.Geological Review(in Chinese),2005,51(3):268-274.
[14]朱艾斓,徐锡伟,周永胜等.川西地区小震重新定位及其活动构造意义.地球物理学报,2005,48(3):629-636.Zhu A L,Xu X W,Zhou Y S,et al.Relocation of smallearthquakes in western Sichuan,China and its implicationsfor active tectonics.Chinese J.Geophys.(in Chinese),2005,48(3):629-636.
[15]Rousseeuw P J,Van Driessen K.A fast algorithm for theminimum covariance determinant estimator.Technometrics,1999,41(3):212-223.
[16]李乡儒,吴福朝,胡占义.均值漂移算法的收敛性.软件学报,2005,16(3):365-374.Li X R,Wu F C,Hu Z Y.Convergence of a mean shiftalgorithm.Journal of Software(in Chinese),2005,16(3):365-374.
[17]周芳芳,樊晓平,叶榛.均值漂移算法的研究与应用.控制与决策,2007,22(8):841-847.Zhou F F,Fan X P,Ye Z.Mean shift research andapplications.Control and Decision(in Chinese),2007,22(8):841-847.
[18]Scott D W,Terrell G R.Biased and unbiased cross validationin density estimation.Journal of the American StatisticalAssociation,1987,82(400):1131-1146.
[19]Lin G.LSH:an earthquake relocation catalog using southernCalifornia pick and waveform data[OL],(2007-5-30)[2011-11-10].http://www.rsmas.miami.edu/personal/glin/LSH.html.
[20]万永革,吴忠良,周公威等.根据震源的两个节面的走向角和倾角求滑动角.地震地磁观测与研究,2000,21(5):26-30.Wan Y G,Wu Z L,Zhou G W,et al.How to get rake angleof the earthquake fault from known strike and dip of the twonodal planes.Seismological and Geomagnetic Observationand Research(in Chinese),2000,21(5):26-30.
[21]方颖,江在森.断裂带变形分析方法研究.大地测量与地球动力学,2011,31(2):53-55,59.Fang Y,Jiang Z S.On fault zone deformation analysismethods.Journal of Geodesy and Geodynamics(in Chinese),2011,31(2):53-55,59.
[22]Wan Y G,Wu Z L,Zhou G W,et al.Global test of seismicstatic stress triggering model.Acta Seismologica Sinica,2002,15(3):318-332.
[23]Wan Y G,Wu Z L,Zhou G W.Focal mechanism dependenceof static stress triggering of earthquakes.Tectonophysics,2004,390(1-4):235-243.
[24]Wan Y G,Shen Z K.Coulomb failure stress changes onfaults caused by the 2008 Mw7.9 Wenchuan earthquake,China.Tectonophysics,2010,491(1-4):105-118.
[25]Steacy S,Nalbant S S,McCloskey J,et al.Onto what planesshould Coulomb stress perturbations be resolvedJ.Geophys.Res.,2005,110:B05S15,doi:10.1029/2004JB003356.
[2]王鸣,王培德.1989年10月18日大同—阳高地震的震源机制和发震构造.地震学报,1992,14(4):407-415.Wang M,Wang P D.The mechanism and seismogenicstructure of Datong-Yanggao earthquake which occurred onOct.18,1989.Acta Seismologica Sinica(in Chinese),1992,14(4):407-415.
[3]王福昌,万永革,胡顺田.粒子群算法在主震断层面参数估计中的应用.地震研究,2008,31(2):149-153.Wang F C,Wan Y G,Hu S T.Application of particle swarmoptimization to the estimation of mainshock fault planeparameters.Journal of Seismological Research(in Chinese),2008,31(2):149-154.
[4]王福昌,曹慧荣,万永革.线性Errors-in-Variables模型在确定汶川地震主震断层面中的应用.数理统计与管理,2010,29(3):381-390.Wang F C,Cao H R,Wan Y G.Application of linear errors-in-variables model for determination main earthquake′s faultparameters of Wenchuan earthquake.Journal of AppliedStatistics and Management(in Chinese),2010,29(3):381-390.
[5]Ansari A,Noorzad A,Zafarani H.Clustering analysis of theseismic catalog of Iran.Computer&Geosciences,2009,35(1):475-486.
[6]Ouillon G,Ducorbier C,Sornette D.Automaticreconstruction of fault networks from seismicity catalogs:Three-dimensional optimal anisotropic dynamic clustering.J.Geophys.Res.,2008,113(B1),doi:10.1029/2007JB005032.
[7]张广伟,雷建设,谢富仁等.华北地区小震精定位及构造意义.地震学报,2011,33(6):699-714.Zhang G W,Lei J S,Xie F R,et al.Precise relocation ofsmall earthquakes occurred in North China and its tectonicimplication.Acta Seismologica Sinica(in Chinese),2011,33(6):699-714.
[8]杨智娴,陈运泰,张宏志.张北—尚义地震序列的重新定位和发震构造.地震学报,2002,24(4):366-377.Yang Z X,Chen Y T,Zhang H Z.Relocation and seismogenicstructure of the 1998 Zhangbei-Shangyi earthquake sequence.Acta Seismologica Sinica(in Chinese),2002,24(4):366-377.
[9]Waldhause F,Ellsworth W L.A double differenceearthquake location algorithm:method and application to theNorthern Hayward fault,California.Bull.Seism.Soc.Amer.,2002,24(4):366-377.
[10]Schaff P D,Waldhauser F.Waveform cross-correlation-baseddifferential travel-time measurements at the NorthernCalifornia Seismic Network.Bull.Seism.Soc.Amer.,2005,95(6):2446-2461.
[11]Lin G Q,Shearer P D,Hauksson E.Applying a three-dimensional velocity model,waveform cross correlation,andcluster analysis to locate southern California seismicity from1981to 2005.J.Geophys.Res.,2007,112:B12309,doi:10.1029/2007JB004986.
[12]吕鹏,丁志峰,朱露培.结合波形互相关的双差定位方法在2008年汶川地震余震序列中的应用.地震学报,2011,33(4):407-419.LüP,Ding Z F,Zhu L P.Application of double differencerelocation technique to aftershocks of 2008 Wenchuanearthquake using waveform cross-correlation.Acta SeismologicaSinica(in Chinese),2011,33(4):407-419.
[13]朱艾斓,徐锡伟,胡平等.首都圈地区小震重新定位及其在地震构造研究中的应用.地质评论,2005,51(3):268-274.Zhu A L,Xu X W,Hu P,et al.Relocation of smallearthquakes in Beijing area and its implication toseismotectonics.Geological Review(in Chinese),2005,51(3):268-274.
[14]朱艾斓,徐锡伟,周永胜等.川西地区小震重新定位及其活动构造意义.地球物理学报,2005,48(3):629-636.Zhu A L,Xu X W,Zhou Y S,et al.Relocation of smallearthquakes in western Sichuan,China and its implicationsfor active tectonics.Chinese J.Geophys.(in Chinese),2005,48(3):629-636.
[15]Rousseeuw P J,Van Driessen K.A fast algorithm for theminimum covariance determinant estimator.Technometrics,1999,41(3):212-223.
[16]李乡儒,吴福朝,胡占义.均值漂移算法的收敛性.软件学报,2005,16(3):365-374.Li X R,Wu F C,Hu Z Y.Convergence of a mean shiftalgorithm.Journal of Software(in Chinese),2005,16(3):365-374.
[17]周芳芳,樊晓平,叶榛.均值漂移算法的研究与应用.控制与决策,2007,22(8):841-847.Zhou F F,Fan X P,Ye Z.Mean shift research andapplications.Control and Decision(in Chinese),2007,22(8):841-847.
[18]Scott D W,Terrell G R.Biased and unbiased cross validationin density estimation.Journal of the American StatisticalAssociation,1987,82(400):1131-1146.
[19]Lin G.LSH:an earthquake relocation catalog using southernCalifornia pick and waveform data[OL],(2007-5-30)[2011-11-10].http://www.rsmas.miami.edu/personal/glin/LSH.html.
[20]万永革,吴忠良,周公威等.根据震源的两个节面的走向角和倾角求滑动角.地震地磁观测与研究,2000,21(5):26-30.Wan Y G,Wu Z L,Zhou G W,et al.How to get rake angleof the earthquake fault from known strike and dip of the twonodal planes.Seismological and Geomagnetic Observationand Research(in Chinese),2000,21(5):26-30.
[21]方颖,江在森.断裂带变形分析方法研究.大地测量与地球动力学,2011,31(2):53-55,59.Fang Y,Jiang Z S.On fault zone deformation analysismethods.Journal of Geodesy and Geodynamics(in Chinese),2011,31(2):53-55,59.
[22]Wan Y G,Wu Z L,Zhou G W,et al.Global test of seismicstatic stress triggering model.Acta Seismologica Sinica,2002,15(3):318-332.
[23]Wan Y G,Wu Z L,Zhou G W.Focal mechanism dependenceof static stress triggering of earthquakes.Tectonophysics,2004,390(1-4):235-243.
[24]Wan Y G,Shen Z K.Coulomb failure stress changes onfaults caused by the 2008 Mw7.9 Wenchuan earthquake,China.Tectonophysics,2010,491(1-4):105-118.
[25]Steacy S,Nalbant S S,McCloskey J,et al.Onto what planesshould Coulomb stress perturbations be resolvedJ.Geophys.Res.,2005,110:B05S15,doi:10.1029/2004JB003356.
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