2003年大姚6.2级、6.1级地震序列震源位置及震源区速度结构的联合反演
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摘要
采用震源位置和速度结构的联合反演方法确定2003年大姚6.2级、6.1级地震序列的分布和震源区的速度结构。该方法首先确定研究区的速度结构,然后在该速度结构的基础上对地震重新定位。结果表明:①大姚6.2级地震序列明显分为地震较密集的东南段和地震较稀疏的北西段,而且这两段存在一定的错动,速度结构也显示出高、低速交界带在错动处具有转折特点;②大姚6.2级地震序列在深度上呈"V"字形分布,这与该地区呈倒三角形分布的低速体相对应,即余震主要分布在高、低速交界带附近;③大姚6.2级、6.1级地震的破裂区都位于倒三角形低速体的东南侧,6.2级地震沿高、低速交界带往下破裂,而6.1级地震沿高、低速交界带往上破裂;④6 km深度的速度分布显示震源区具有高、低速度体交替呈四象限分布特征,而且余震主要沿北西向的高低速交界带分布;⑤大姚6.2级主震的东南侧的高、低速交界带处的低速体速度值较北西侧低速值高,其对6.2级地震往东南方向破裂具有阻碍作用,即东南侧处于能量积累状态,有利于6.1级地震的发生。
We determined the 2003 Dayao M6.2 and M6.1 earthquakes sequence location and velocity structure of the hypocentral area by a simultaneous inversion method.First the velocity structure is determined by the method,and then earthquake location is performed on the basis of velocity structure.The results show that the M6.2 earthquake sequence can divided into two segments,the relatively dense southeast segment and the relatively sparse northwest segment,and there is a dip offset between the two segments,characterized by a turn.At the transitional zone of high and low velocity structures.The distribution of the M6.2 earthquake sequences shows a "V" shape along the depth,which corresponds to the reversing triangle shape of low velocity structure,namely,the aftershocks of M6.2 are distributed along the transitional zones of high and low velocity structures.The rupture zones of the M6.2 and M6.1 earthquakes are located on the southeast side of the reversing triangle shape of low velocity structure.The mainshock of M6.2 ruptured downwards and the mainshock of M6.1 ruptured upwards along the transitional zones of high and low velocity structure.The velocity structure at the depth of 6km shows that there is the quadrant distribution of high and low velocity structures and the aftershocks of the M6.2 and M6.1 earthquakes are distributed along the northwest transitional zones of high and low velocity structure.The value of low velocity structure at the southeast side of the M6.2 earthquake is higher than the value of low velocity structure at the northwest side,which is disadvantageous to the rupture southeastward for the M6.2 earthquake and is advantageous to the energy accumulation and occurrence of the M6.1 earthquake.
We determined the 2003 Dayao M6.2 and M6.1 earthquakes sequence location and velocity structure of the hypocentral area by a simultaneous inversion method.First the velocity structure is determined by the method,and then earthquake location is performed on the basis of velocity structure.The results show that the M6.2 earthquake sequence can divided into two segments,the relatively dense southeast segment and the relatively sparse northwest segment,and there is a dip offset between the two segments,characterized by a turn.At the transitional zone of high and low velocity structures.The distribution of the M6.2 earthquake sequences shows a "V" shape along the depth,which corresponds to the reversing triangle shape of low velocity structure,namely,the aftershocks of M6.2 are distributed along the transitional zones of high and low velocity structures.The rupture zones of the M6.2 and M6.1 earthquakes are located on the southeast side of the reversing triangle shape of low velocity structure.The mainshock of M6.2 ruptured downwards and the mainshock of M6.1 ruptured upwards along the transitional zones of high and low velocity structure.The velocity structure at the depth of 6km shows that there is the quadrant distribution of high and low velocity structures and the aftershocks of the M6.2 and M6.1 earthquakes are distributed along the northwest transitional zones of high and low velocity structure.The value of low velocity structure at the southeast side of the M6.2 earthquake is higher than the value of low velocity structure at the northwest side,which is disadvantageous to the rupture southeastward for the M6.2 earthquake and is advantageous to the energy accumulation and occurrence of the M6.1 earthquake.
引文
[1]华卫,刘杰,郑斯华,等.2003年云南大姚6.2级、6.1级地震序列特征分析及触发研究[J].中国地震,2006,22(1):10-23.
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[4]Gomberg J S,Shedlock K M,Roecker S W.The effect of S-wave arrival times on the accuracy ofhypocenter estimation[J].Bull Seism Soc Am,1990,80:1 605-1 628.
[5]Geiger L.Probability method for the determination of earthquake epicenters from arrival time only[J].Bull St Louis Univ,1912,8:60-71.
[6]Poupinet G,Ellsworth W L,Fréchet J.Monitoring velocity variations in the crust using earthquakedoublets:an application to the Calaveras fault,California[J].J Geophys Res,1984,89:5 719-5 731.
[7]Got J L,Fréchet J,Klein F W.Deep fault plane geometry inferred from multiplet relative relocationbeneath the south flank of Kilauea[J].J Geophys Res,1994,99:15 375-15 386.
[8]Spence W.Relative epicenter determination using P-wave arrival-time differences[J].Bull Seism SocAm,1980,70:171-183.
[9]Ito A.High resolution relative hypocenters of similar earthquakes by cross-spectral analysis method[J].J Phys Earth,1985,33:279-294.
[10]Frémont M J,Malone S D.High precision Relative locations of earthquakes at Mount St.Helens,Washington[J].J Geophys Res,1987,92:10 223-10 236.
[11]周仕勇,许忠淮,韩京,等.主地震定位方法分析及1997年新疆伽师震群高精度定位[J].地震学报,1999,21(3):258-265.
[12]Waldhauser F,Ellsworth W L.A double-difference earthquake location algorithm:Method and Ap-plication to the Northern Hayward fault[J].Bull Seis Soc Amer,2000,90(6):1 353-1 368.
[13]Aki K,Lee W H K.Determination of three-dimensional velocity anomalies under a seismic array u-sing P arrival times from local earthquakes.1.A homogeneous initial model[J].J Geophys Res,1976,81:4 381-4 399.
[14]Thurber C H.Earthquake locations and three-dimensional crustal structure in the Coyote late area,Central California[J].J Geophys Res,1983,88:8 226-8 236.
[15]刘福田,李强,吴华,等.用于速度图像重建的层析成像法[J].地球物理学报,1989,32(1):46-61.
[16]Zhao D,Hasegawa A,Horiuchi S.Tomographic imaging of P and S wave velocity structure beneathnortheastern Japan[J].J Geophys Res,1992,97:19 909-19 928.
[17]Smith G P,Ekstrom G.Improve teleseismic event location using a three-dimensional earth model[J].Bull Seism Soc Am,1996,86:788-796.
[18]Crosson R S.Crustal structure modeling of earthquake data,1,Simultaneous least squares estima-tion of hypocenter and velocity parameters[J].J Geophys Res,1976,81:3 036-3 046.
[19]Pavlis L G,Booker J R.The mixed discrete-continuous inverse problem:application to the simul-taneous determination of earthquake hypocenters and velocity structure[J].J Geophys Re,1980,85:4 801-4 810.
[20]Spencer C,Gubbins D.Travel time inversion for simultaneous earthquake location and velocitystructure determination in laterally varying media[J].Geophys J R Astron Soc,1980,63(1):95-116.
[21]刘福田.震源位置和速度结构的联合反演(Ⅰ)——理论和方法[J].地球物理学报,1984,27(2):167-175.
[22]Michael A J.Effects of three-dimensional velocity structure on the seismicity of the 1984 MorganHill,California,aftershock sequence[J].Bull Seism Soc Am,1988,78:1 199-1 221.
[23]Kissling E,Ellsworth W L,Eberhard-Phillips D,et al.Initial reference models in local earthquaketomography[J].J Geophys Res,1994,99:19 635-19 646.
[24]胡鸿翔,陆涵行,王椿墉,等.滇西地区地壳结构的爆破地震研究[J].地球物理学报,1986,29(2):133-144.
[25]刘建华,刘福田,吴华,等.中国南北带地壳和上地幔的三维速度结构[J].地球物理学报,1989,32(2):143-151.
[26]陈培善,刘福田,李强,等.云南地区速度结构的横向不均匀性[J].中国科学(B),1990,(4):431-438.
[27]王椿镛,王溪莉,颜其中.昆明地震台网下方的三维速度结构[J].地震学报,1994,16(2):167-175.
[28]王椿镛,Mooney W D,王溪莉,等.川滇地区地壳上地幔三维速度结构研究[J].地震学报,2002,24(1):1-16.
[29]何正勤,叶太兰,苏伟.云南地区地壳中上部横波速度结构研究[J].地球物理学报,2004,47(5):838-844.
[30]Zhou H.Direct inversion of velocity interfaces[J].Geophys Res Lett,2004,7:doi:10.1029/2003GL019318.
[31]Paige C C,Saunders M A.LSQR:Sparse linear equations and least squares problems[J].ACMTransactions on Mathematical Software,1982,8(2):195-209.
[32]Humphreys E,Clayton R W.Adaptation of back projection tomography to seismic travel time prob-lems[J].J Geophys Res,1988,93:1 073-1 085.
[2]苏有锦.2003年7月21日、10月16日云南大姚6.2级和6.1级地震预测预报回顾与讨论[J].国际地震动态,2004,(1):18-21.
[3]Pavlis G L.Appraising earthquake hypocenter location errors:a complete,practical approach forsingle-event locations[J].Bull Seism Soc Am,1986,76:1 699-1 710.
[4]Gomberg J S,Shedlock K M,Roecker S W.The effect of S-wave arrival times on the accuracy ofhypocenter estimation[J].Bull Seism Soc Am,1990,80:1 605-1 628.
[5]Geiger L.Probability method for the determination of earthquake epicenters from arrival time only[J].Bull St Louis Univ,1912,8:60-71.
[6]Poupinet G,Ellsworth W L,Fréchet J.Monitoring velocity variations in the crust using earthquakedoublets:an application to the Calaveras fault,California[J].J Geophys Res,1984,89:5 719-5 731.
[7]Got J L,Fréchet J,Klein F W.Deep fault plane geometry inferred from multiplet relative relocationbeneath the south flank of Kilauea[J].J Geophys Res,1994,99:15 375-15 386.
[8]Spence W.Relative epicenter determination using P-wave arrival-time differences[J].Bull Seism SocAm,1980,70:171-183.
[9]Ito A.High resolution relative hypocenters of similar earthquakes by cross-spectral analysis method[J].J Phys Earth,1985,33:279-294.
[10]Frémont M J,Malone S D.High precision Relative locations of earthquakes at Mount St.Helens,Washington[J].J Geophys Res,1987,92:10 223-10 236.
[11]周仕勇,许忠淮,韩京,等.主地震定位方法分析及1997年新疆伽师震群高精度定位[J].地震学报,1999,21(3):258-265.
[12]Waldhauser F,Ellsworth W L.A double-difference earthquake location algorithm:Method and Ap-plication to the Northern Hayward fault[J].Bull Seis Soc Amer,2000,90(6):1 353-1 368.
[13]Aki K,Lee W H K.Determination of three-dimensional velocity anomalies under a seismic array u-sing P arrival times from local earthquakes.1.A homogeneous initial model[J].J Geophys Res,1976,81:4 381-4 399.
[14]Thurber C H.Earthquake locations and three-dimensional crustal structure in the Coyote late area,Central California[J].J Geophys Res,1983,88:8 226-8 236.
[15]刘福田,李强,吴华,等.用于速度图像重建的层析成像法[J].地球物理学报,1989,32(1):46-61.
[16]Zhao D,Hasegawa A,Horiuchi S.Tomographic imaging of P and S wave velocity structure beneathnortheastern Japan[J].J Geophys Res,1992,97:19 909-19 928.
[17]Smith G P,Ekstrom G.Improve teleseismic event location using a three-dimensional earth model[J].Bull Seism Soc Am,1996,86:788-796.
[18]Crosson R S.Crustal structure modeling of earthquake data,1,Simultaneous least squares estima-tion of hypocenter and velocity parameters[J].J Geophys Res,1976,81:3 036-3 046.
[19]Pavlis L G,Booker J R.The mixed discrete-continuous inverse problem:application to the simul-taneous determination of earthquake hypocenters and velocity structure[J].J Geophys Re,1980,85:4 801-4 810.
[20]Spencer C,Gubbins D.Travel time inversion for simultaneous earthquake location and velocitystructure determination in laterally varying media[J].Geophys J R Astron Soc,1980,63(1):95-116.
[21]刘福田.震源位置和速度结构的联合反演(Ⅰ)——理论和方法[J].地球物理学报,1984,27(2):167-175.
[22]Michael A J.Effects of three-dimensional velocity structure on the seismicity of the 1984 MorganHill,California,aftershock sequence[J].Bull Seism Soc Am,1988,78:1 199-1 221.
[23]Kissling E,Ellsworth W L,Eberhard-Phillips D,et al.Initial reference models in local earthquaketomography[J].J Geophys Res,1994,99:19 635-19 646.
[24]胡鸿翔,陆涵行,王椿墉,等.滇西地区地壳结构的爆破地震研究[J].地球物理学报,1986,29(2):133-144.
[25]刘建华,刘福田,吴华,等.中国南北带地壳和上地幔的三维速度结构[J].地球物理学报,1989,32(2):143-151.
[26]陈培善,刘福田,李强,等.云南地区速度结构的横向不均匀性[J].中国科学(B),1990,(4):431-438.
[27]王椿镛,王溪莉,颜其中.昆明地震台网下方的三维速度结构[J].地震学报,1994,16(2):167-175.
[28]王椿镛,Mooney W D,王溪莉,等.川滇地区地壳上地幔三维速度结构研究[J].地震学报,2002,24(1):1-16.
[29]何正勤,叶太兰,苏伟.云南地区地壳中上部横波速度结构研究[J].地球物理学报,2004,47(5):838-844.
[30]Zhou H.Direct inversion of velocity interfaces[J].Geophys Res Lett,2004,7:doi:10.1029/2003GL019318.
[31]Paige C C,Saunders M A.LSQR:Sparse linear equations and least squares problems[J].ACMTransactions on Mathematical Software,1982,8(2):195-209.
[32]Humphreys E,Clayton R W.Adaptation of back projection tomography to seismic travel time prob-lems[J].J Geophys Res,1988,93:1 073-1 085.
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