2003年大姚地震震中区的速度和衰减结构
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摘要
使用2003年7月21日和10月20日云南省大姚县M6.2、M6.1地震震后流动数字化地震监测台网所记录的地震走时和波形资料,反演了震中区的Vp、Vs和Qp的三维结构.前人根据余震分布推测该震区存在一条北西西走向右旋走滑断裂带.三维结果表明,Vp和Qp的低值异常可以佐证该断裂带的存在;但除此断裂带,可能还存在一条北北东向断裂带,倾向西,表现为低Vp、Vs以及低Qp异常,并且异常深度达到8~10km.因此,大姚震中区可能存在两条相互交错的断层,这与整个南北带断层的交错特征非常相似.另外我们推断该北北东向断裂带在南北方向可能有较长的延伸.
By inversion of travel time and waveform data recorded by a temporary seismic network installed after the 21 July 2003 M6.2 and the 20 October 2003 M6.1 Dayao earthquakes in Yunnan province, three-dimensional (3-D) V_p, V_s and Q_p structures of the focal area were obtained. The 3-D imaging results show obvious low-V_p and low-Q_p anomalies, which corroborates the previous speculation from aftershock distribution that a NWW right lateral fault exists in the focal area. Besides that fault, there probably also exists a NNE fault which dips westward and exhibits low-V_p, low-V_s and low-Q_p features down to the depth of 8～10 km. According to these observations, we infer that in the Dayao focal area there are likely two faults intersecting with each other, similar to the intersecting faults ubiquitously observed in the whole North-South zone. We also suggest that the NNE fault may extend further to both north and south.
By inversion of travel time and waveform data recorded by a temporary seismic network installed after the 21 July 2003 M6.2 and the 20 October 2003 M6.1 Dayao earthquakes in Yunnan province, three-dimensional (3-D) V_p, V_s and Q_p structures of the focal area were obtained. The 3-D imaging results show obvious low-V_p and low-Q_p anomalies, which corroborates the previous speculation from aftershock distribution that a NWW right lateral fault exists in the focal area. Besides that fault, there probably also exists a NNE fault which dips westward and exhibits low-V_p, low-V_s and low-Q_p features down to the depth of 8～10 km. According to these observations, we infer that in the Dayao focal area there are likely two faults intersecting with each other, similar to the intersecting faults ubiquitously observed in the whole North-South zone. We also suggest that the NNE fault may extend further to both north and south.
引文
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[31]宋方敏,汪一鹏,俞维贤等.小江活动断裂带.北京:地震出版社,1998Song F M,Wang Y P,Yu W X,et al.Xiaojiang Active Faults.Beijing:Seismological Press,1998
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[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.国际地震动态,2004,1:18~21Su YJ.Review and discussion for DayaoM6.2andM6.1in Yunnan province onJul.21and Oct.16,2003.Recent Developments in World Seismology(in Chinese),2004,1:18~31
[3]马丽芳主编.中国地质图集.北京:地质出版社,2002.293~295Ma L Fed.Geological Map Sets of China(in Chinese).Beijing:Geological Publishing House,2002.293~295
[4]邓起东,张培震,冉勇康等.中国活动构造基本特征.中国科学(D辑),2002,45(12):1020~1030Deng QD,Zhang P Z,Rang Y K,et al.Basic characters of active geological structures in China.Science in China(Series D)(in Chinese),2002,45(12):1020~1030
[5]华卫,刘杰,郑斯华等.2003年云南大姚6.2、6.1级地震序列特征分析及地震触发研究.中国地震,2006,22(1):10~23Hua W,Liu J,Zheng S H,et al.The characteristic analysis and seismic triggering study of the DayaoM6.2andM6.1earthquake sequences in2003.Earthquake Research in China(in Chinese),2006,22(1):10~23
[6]Wang C Y,Chan W W,Mooney WD.Three-dimensional velocity structure of crust and upper mantle in southwestern China and its tectonic implications.J.Geophys.Res.,2003,108(B9):2442,doi:10.1029/2002JB001973
[7]He Z Q,Ye T L,Su W.3-D velocity structure of the middle andupper crust in the Yunnan region,China.Pure Appl.Geophys.,2005,162:2355~2368
[8]Eberhart-Phillips D,Chadwick M.Three-dimensional attenuation model of the shallow Hikurangi subduction zone in the Raukumara Peninsula,New Zealand.Geophys.Res.,2002,107:2033,doi:10.1029/2000JB000046
[9]Gori D,Chiarabba P C,Patane D.Qpstructure of Mount Etna:Constraints for the physics of the plumbing system.J.Geophys.Res.,2005,110,B05303,doi:10.1029/2003JB002875
[10]Hauksson E,Shearer P M.Attenuation models(QpandQs)inthree dimensions of the southern California crust:Inferred fluid saturation at seismogenic depths.J.Geophys.Res.2006,111:302,doi:10.1029/2005JB003947
[11]Romanowicz B.Global mantle tomography:progress statusinthe last10years.Annu.Rev.Geoph.(Space Phys),2003,31(1):303
[12]秦嘉政,叶建庆,蔡绍平等.云南大姚地震近源数字地震观测与现代新参数报告.北京:地震出版社,2005Qin J Z,Ye J Q,Cai Z P,et al.Reports on observation of Dayao earthquake in Yunnan province recorded in the near source digital seismic network and the modern new parameters(in Chinese).Beijing:Seismological Press,2005
[13]Klein F W.User’s Guide to HYPOINVERSE-2000,a Fortran Programto Solve for Earthquake Locations and Magnitudes.http://geopubs.wr.usgs.gov/open-file/of02-171/
[14]Kissling E,Ellsworth W L,Eberhart-phillips D,et al.Initial reference models in local earthquake tomography.J.Geophys.Res.,1994,99:19635~19646
[15]Thurber C H,Eberhart-Phillips D.Local earthquaketomography with flexible gridding.Computers and Geoscience,1999,25:809~818
[16]Wadati K.Onthetravel time of earthquake waves.Geophys.Mag.,1933,7:101~111
[17]UmJ,Thurber C.Afast algorithmfor two-point seismic raytracing.Bulletin ofthe Seismological Society of America,1987,77(3):972~986
[18]Brune J N.Tectonic stress and spectra of seismic shear waves from earthquakes.J.Geophys.Res.,1970,75:4997~5009
[19]Rietbrock A.Development of an interactive analysis systemfor large seismological data sets:application to the determination of the absorption structure in the Loma Prieta region California[Ph.D.thesis].Ludwig-Maximulians-Universitat Munchen,Munchen,Germany,1996
[20]Thomson DJ.Spectrum estimation and harmonic analysis.Proceedings ofthe IEEE,1982,70:1055~1096
[21]Mor啨J J.The Levenberg-Marquardt algorithm:Implementation and theory numerical analysis.In:Watson G A ed.Lecture Notes in Mathematics630.Springer Verlag,1977.105~116
[22]Goldberg D E.Genetic Algorithms in Search,Optimization and Machine Learning.Boston:Kluwer Academic Publishers,1989
[23]Mishra OP,Zhao DP.Crack density,saturationrate and porosity at the2001Bhuj,India,earthquake hypocenter:a fluid-driven earthquake?Earth Planet Sci.Lett.,2003,212:393~405
[24]齐诚,赵大鹏,陈等.首都圈地区地壳P波和S波三维速度结构及其与大地震的关系.地球物理学报,2006,49(3):805~815Qi C,Zhao D P,Chen Y,et al.3-D P and S wave velocity structures andtheir relationship to strong earthquakes in the Chinese capital region.Chinese J.Geophys.(in Chinese),2006,49(3):805~815
[25]Mukhopadhyay S,Mishra OP,Zhao D,et al.3-Dseismic structure of the source area of the1993Latur,India,earthquake and its implications for rupture nucleations.Tectonophysics,2006,415:1~16
[26]Nur A.Seismic rock properties for reservoir descriptions and monitoring.In:Nolet Ged.Seismic Tomography:with Applications in Global Seismology and Exploration Geophysics.Boston:Kluwer Academic Publishers,1987.203~237
[27]邓起东,王挺梅,李建国等.关于海城地震震源模式的讨论.地质科学,1976,3:195~204Deng QD,Wang T M,Li J G,et al.Adiscussion onsource model of Haicheng earthquake.Chinese Jour.Geol.(formerly,Scientia Geologica Sinica)(in Chinese),1976,3:195~204
[28]张四昌.中国大陆共扼地震构造研究.中国地震,1991,2(7):69~76Zhang S C.Studies of conjugate seismotectonics of the continental earthquakes in China.Earthquake Research in China(in Chinese),1991,2(7):69~76
[29]Zhang HJ,Liu Y F,Xu Z,et al.Characterizing high-resolution seismic velocity and attenuation structure of the Yunnan region,Southwest China,using double-difference tomography.AGU Fall Meeting,2006
[30]乔学军,王琪,杜瑞林.川滇地区活动地块现今地壳形变特征.地球物理学报,2004,47(5):805~811Qiao XJ,Wang Q,Du R L.Characteristics of current crustal deformation of active blocks in the Sichuan-Yunnan region.Chinese J.Geophys.(in Chinese),2004,47(5):805~811
[31]宋方敏,汪一鹏,俞维贤等.小江活动断裂带.北京:地震出版社,1998Song F M,Wang Y P,Yu W X,et al.Xiaojiang Active Faults.Beijing:Seismological Press,1998
[32]杨智娴,陈运泰,郑月军等.双差地震定位法在我国西部地区地震精确定位中的应用.中国科学(D辑),2003,33(增刊):129~134Yang Z X,Chen Y T,Zheng Y J,et al.Accurate relocation of earthquakes in central-western China using the double-difference earthquake location algorithm.Science in China(Series D),2003,46(S2):181~188,DOI:10.1360/03dz0014
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