远震体波有限破裂过程反演敏感性测试及其在汶川地震上的应用
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摘要
本文利用远震P和SH波反演得到2008年5月12日汶川大地震(MW=7.9)的一系列有限破裂模型。使用一种基于小波变换的模拟退火非线性反演方法,我们将主断层划分成若干个子断层,在反演时同时确定每个子断层上的滑移量、滑动角、上升时间(risetime)以及平均破裂速度。我们首先根据一个假定的破裂模型生成理论地震图,将该理论地震数据作为输入进行反演,对该有限破裂反演方法进行了一系列测试,以验证反演对断层倾角、平均破裂速度、最大破裂深度等参数的敏感性。然后我们采用4个不同倾角的断层面来对汶川地震远震体波记录进行反演。结果表明,若对只在一个断层面上模拟该地震,30°倾角是个较为合适的值。反演的结果还表明,此次地震有两个主要的能量释放区域,并且主断层面存在倾角变化的可能性。在将来的研究中,可以结合GPS,InSAR测地学以及强震等数据,来对强震的破裂过程做更细致的研究。
We present a series of rupture models of the Wenchuan MW7.9 earthquake based on inverting P and SH teleseismic body waves.A simulated annealing algorithm is used to determine the finite-fault model that minimizes the objective function described in terms of wavelet coefficients.With this approach,we can simultaneously invert for the slip amplitude,slip direction,rise time and rupture velocity.At the first step,experiments conducted on synthetic data are used to assess the ability to recover rupture slip details and teleseismic body waves.We investigate the resolvability of teleseismic body inversion on dip angle,rupture velocity and maximum rupture depth.Then 4 slip models are obtained for the Wenchuan earthquake by applying this method on 4 single fault planes which are specified by different dip angle.We analysis the resolvability of finite fault analysis by using telesesimic data and how to choose a reasonable dip angle for the Wenchuan earthquake.Two asperities are observed on different solutions,and likelihood of change dip is discussed.Incremental improvements in resolving for source complexity will be possible in the near future with more geodetic data and near field seismic data combined with space-based observations.
We present a series of rupture models of the Wenchuan MW7.9 earthquake based on inverting P and SH teleseismic body waves.A simulated annealing algorithm is used to determine the finite-fault model that minimizes the objective function described in terms of wavelet coefficients.With this approach,we can simultaneously invert for the slip amplitude,slip direction,rise time and rupture velocity.At the first step,experiments conducted on synthetic data are used to assess the ability to recover rupture slip details and teleseismic body waves.We investigate the resolvability of teleseismic body inversion on dip angle,rupture velocity and maximum rupture depth.Then 4 slip models are obtained for the Wenchuan earthquake by applying this method on 4 single fault planes which are specified by different dip angle.We analysis the resolvability of finite fault analysis by using telesesimic data and how to choose a reasonable dip angle for the Wenchuan earthquake.Two asperities are observed on different solutions,and likelihood of change dip is discussed.Incremental improvements in resolving for source complexity will be possible in the near future with more geodetic data and near field seismic data combined with space-based observations.
引文
[1]Beroza G,Squdich P.Liearizedinversion of fault behavior:applicationto the1984Moran Hill,Cali-fornia earthquake[J].J Geophys Res,1988,93:6275-6296.
[2]Burchfiel B C,Royden L H,Vander Hilst R D,et al.Ageological and geophysical context for the Wenchuan earthquake of12May2008sichuan people′s republic of China[J].GSA Today,2008,18:4-11.
[3]Cohee B P,Beroza G C.Slip Distribution of the1992Landers Earthquake and Its Implications for Earthquake Source Mechanics[J].BSSA,1994,84(3):692-712.
[4]Das S,Kostrov B V.Inversion for Seismic Slip Rate History and Distribution with Stabilizing Con-straints-Application to the1986Andreanof-Islands Earthquake[J].J Geophysi Res,1990,95(B5):6899-6913.
[5]Fukuyama E,Mikumo T.Dynamic Rupture Analysis-Inversion for the Source Process of the1990Izu-Oshima,Japan,Earthquake(M=6.5)[J].J Geophysi Res,1993,98(B4):6529-6542.
[6]Guatteri M,Spudich P.What can strong-motion data tell us about slip-weakening fault-friction laws-[J].BSSA,2000,90(1):98116.
[7]Hartzell S,Liu P C.Calculation of earthquake rupture histories using a hybrid global search algo-rithm:Application to the1992Landers,California,earthquake[J].Physics of the Earth and Plane-tary Interiors,1996,95(1-2):79-99.
[8]Hartzell S,Liu P C,Mendoza C.The1994Northridge,California,earthquake:Investigation of rupture velocity,risetime,and high-frequency radiation[J].J Geophysi Res,1996,101(B9):20091-20108.
[9]Hartzell S H,Heaton T H.Inversion of strong-motion and teleseismic waveform data for the faultrupture history of the1979Imperial Valley,California,earthquake[J].BSSA,1983,73:1553-1583.
[10]Hudnut K W,Shen Z,Murray M,et al.Co-seismic displacements of the1994Northridge,Califor-nia,earthquake[J].BSSA,1996,86(1):S19-S36.
[11]Ji C,Hel mberger D V,Wald,DJ.Ateleseismic study of the2002Denali fault,Alaska,earthquake and implications for rapid strong-motion estimation[J].Earthquake Spectra,2004,20(3):617-637.
[12]Ji C,Hel mberger D V,Wald DJ,et al.Slip history and dynamic implications of the1999Chi-Chi,Tai wan,earthquake[J].J Geophysi Res,2003,108(B9):-.
[13]Ji C,Wald D J,Hel mberger D V.Source description of the1999Hector Mine,California,earth-quake,part I:Wavelet domaininversion theory and resolution analysis[J].BSSA,2002a,92(4):1192-1207.
[14]Ji C,Wald D J,Hel mberger D V.Source description of the1999Hector Mine,California,earth-quake,partⅡ:Complexity of slip history[J].BSSA,2002b,92(4):1208-1226.
[15]Kikuchi H,Kanamori H.Inversion of complex body waves——Ⅰ[J].BSSA,1982,72(2):491-506.
[16]Langer C J,Hartzell S.Rupture distribution of the1977western Argentina earthquake[J].Physics of the Earth and Planetary Interiors,1996,94(1-2):121-132.
[17]Mendoza C,Hartzell S.Inversion fro slip distribution using teleseismic P waveform:North Pal m Springs,Boirth Peak,and Michoacan earthquake[J].Bull Seism Soc Am,1988,78:1092-1111.
[18]Olson a H,Apsel RJ.Finite fault andinversiontheory with applicationto the1979Implerial Valley earthquake[J].Bull Seism Soc Am,1982,72:1969-2001.
[19]Peltzer G,Rosen P.Surface Displacements of the17May1993Eureka Valley,California,Earth-quake Observed by Sar Interferometry[J].Science,1995,268(5215):1333-1336.
[20]Pino N A,Mazza S,Boschi E.Rupture directivity of the major shocks in the1997Umbria-Marche(Central Italy)sequence from regional broadband waveforms[J].Geophysical Research Letters,1999,26(14):2101-2104.
[21]Rothman D H.Automatic estimation of large residual statics corrections[J].Geophysics,1986,51:337-346.
[22]Scholz C H.The Mechanics of Earthquakes and Faulting[M].Cambridge:Cambridge University Press,1990.
[23]Stramondo S,Tesauro M,Briole P,et al.The September26,1997Colfiorito,Italy,earthquakes:modeled coseismic surface displacement fromSARinterferometry and GPS[J].Geophysical Research Letters,1999,26(7):883-886.
[24]Wald DJ,Heaton T H,Hudnut K W.The slip history of the1994Northridge,California,earth-quake determined from strong-motion,teleseismic,GPS,and leveling data[J].BSSA,1996,86(1):S49-S70.
[25]Ward DJ,Barrientos S E.Aninversion for slip distribtuion and fault shape from geodetic observa-tions of1983,Borch Peak,Idaho,earthquake[J].J Geophys Res,1986,91:4909-4919.
[26]Yomogida K.Detection of Anomalous Seismic Phases by the Wavelet Transform[J].Geophysical Journal International,1994,116(1):119-130.
[27]Zeng Y H,Anderson J G.Acomposite source model of the1994Northridge earthquake using genet-ic algorithms[J].BSSA,1996,86(1):S71-S83.
[28]何玉梅,郑天愉,单新建.1996年3月19日新疆阿图什6.9级地震:单侧破裂过程[J].地球物理学报,2001,44:510-519.
[29]姚振兴,纪晨.时间域有限地震断层的反演问题[J].地球物理学报,1997,40:691-701.
[30]刘鹏程,纪晨,Hartzell H.改进的模拟退火-单纯形综合反演方法[J].地球物理学报,1995,38:350-357.
[31]赵珠,范军,郑斯华,等.龙门山断裂带地壳速度结构和震源位置的精确修订[J].地震学报,1997,19:615-622.
[32]王卫民,赵连锋,李娟,等.四川汶川8.0级地震震源过程[J].地球物理学报,2008,51(5):1403-1410.
[33]张勇,冯万鹏,许力生,等.2008年汶川大地震的时空破裂过程[J].中国科学D辑:地球科学,2008,38(10):1186-1194.
[2]Burchfiel B C,Royden L H,Vander Hilst R D,et al.Ageological and geophysical context for the Wenchuan earthquake of12May2008sichuan people′s republic of China[J].GSA Today,2008,18:4-11.
[3]Cohee B P,Beroza G C.Slip Distribution of the1992Landers Earthquake and Its Implications for Earthquake Source Mechanics[J].BSSA,1994,84(3):692-712.
[4]Das S,Kostrov B V.Inversion for Seismic Slip Rate History and Distribution with Stabilizing Con-straints-Application to the1986Andreanof-Islands Earthquake[J].J Geophysi Res,1990,95(B5):6899-6913.
[5]Fukuyama E,Mikumo T.Dynamic Rupture Analysis-Inversion for the Source Process of the1990Izu-Oshima,Japan,Earthquake(M=6.5)[J].J Geophysi Res,1993,98(B4):6529-6542.
[6]Guatteri M,Spudich P.What can strong-motion data tell us about slip-weakening fault-friction laws-[J].BSSA,2000,90(1):98116.
[7]Hartzell S,Liu P C.Calculation of earthquake rupture histories using a hybrid global search algo-rithm:Application to the1992Landers,California,earthquake[J].Physics of the Earth and Plane-tary Interiors,1996,95(1-2):79-99.
[8]Hartzell S,Liu P C,Mendoza C.The1994Northridge,California,earthquake:Investigation of rupture velocity,risetime,and high-frequency radiation[J].J Geophysi Res,1996,101(B9):20091-20108.
[9]Hartzell S H,Heaton T H.Inversion of strong-motion and teleseismic waveform data for the faultrupture history of the1979Imperial Valley,California,earthquake[J].BSSA,1983,73:1553-1583.
[10]Hudnut K W,Shen Z,Murray M,et al.Co-seismic displacements of the1994Northridge,Califor-nia,earthquake[J].BSSA,1996,86(1):S19-S36.
[11]Ji C,Hel mberger D V,Wald,DJ.Ateleseismic study of the2002Denali fault,Alaska,earthquake and implications for rapid strong-motion estimation[J].Earthquake Spectra,2004,20(3):617-637.
[12]Ji C,Hel mberger D V,Wald DJ,et al.Slip history and dynamic implications of the1999Chi-Chi,Tai wan,earthquake[J].J Geophysi Res,2003,108(B9):-.
[13]Ji C,Wald D J,Hel mberger D V.Source description of the1999Hector Mine,California,earth-quake,part I:Wavelet domaininversion theory and resolution analysis[J].BSSA,2002a,92(4):1192-1207.
[14]Ji C,Wald D J,Hel mberger D V.Source description of the1999Hector Mine,California,earth-quake,partⅡ:Complexity of slip history[J].BSSA,2002b,92(4):1208-1226.
[15]Kikuchi H,Kanamori H.Inversion of complex body waves——Ⅰ[J].BSSA,1982,72(2):491-506.
[16]Langer C J,Hartzell S.Rupture distribution of the1977western Argentina earthquake[J].Physics of the Earth and Planetary Interiors,1996,94(1-2):121-132.
[17]Mendoza C,Hartzell S.Inversion fro slip distribution using teleseismic P waveform:North Pal m Springs,Boirth Peak,and Michoacan earthquake[J].Bull Seism Soc Am,1988,78:1092-1111.
[18]Olson a H,Apsel RJ.Finite fault andinversiontheory with applicationto the1979Implerial Valley earthquake[J].Bull Seism Soc Am,1982,72:1969-2001.
[19]Peltzer G,Rosen P.Surface Displacements of the17May1993Eureka Valley,California,Earth-quake Observed by Sar Interferometry[J].Science,1995,268(5215):1333-1336.
[20]Pino N A,Mazza S,Boschi E.Rupture directivity of the major shocks in the1997Umbria-Marche(Central Italy)sequence from regional broadband waveforms[J].Geophysical Research Letters,1999,26(14):2101-2104.
[21]Rothman D H.Automatic estimation of large residual statics corrections[J].Geophysics,1986,51:337-346.
[22]Scholz C H.The Mechanics of Earthquakes and Faulting[M].Cambridge:Cambridge University Press,1990.
[23]Stramondo S,Tesauro M,Briole P,et al.The September26,1997Colfiorito,Italy,earthquakes:modeled coseismic surface displacement fromSARinterferometry and GPS[J].Geophysical Research Letters,1999,26(7):883-886.
[24]Wald DJ,Heaton T H,Hudnut K W.The slip history of the1994Northridge,California,earth-quake determined from strong-motion,teleseismic,GPS,and leveling data[J].BSSA,1996,86(1):S49-S70.
[25]Ward DJ,Barrientos S E.Aninversion for slip distribtuion and fault shape from geodetic observa-tions of1983,Borch Peak,Idaho,earthquake[J].J Geophys Res,1986,91:4909-4919.
[26]Yomogida K.Detection of Anomalous Seismic Phases by the Wavelet Transform[J].Geophysical Journal International,1994,116(1):119-130.
[27]Zeng Y H,Anderson J G.Acomposite source model of the1994Northridge earthquake using genet-ic algorithms[J].BSSA,1996,86(1):S71-S83.
[28]何玉梅,郑天愉,单新建.1996年3月19日新疆阿图什6.9级地震:单侧破裂过程[J].地球物理学报,2001,44:510-519.
[29]姚振兴,纪晨.时间域有限地震断层的反演问题[J].地球物理学报,1997,40:691-701.
[30]刘鹏程,纪晨,Hartzell H.改进的模拟退火-单纯形综合反演方法[J].地球物理学报,1995,38:350-357.
[31]赵珠,范军,郑斯华,等.龙门山断裂带地壳速度结构和震源位置的精确修订[J].地震学报,1997,19:615-622.
[32]王卫民,赵连锋,李娟,等.四川汶川8.0级地震震源过程[J].地球物理学报,2008,51(5):1403-1410.
[33]张勇,冯万鹏,许力生,等.2008年汶川大地震的时空破裂过程[J].中国科学D辑:地球科学,2008,38(10):1186-1194.
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