复杂速度模型的地震交切定位方法(英文)
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摘要
交切法是最基本的地震定位方法之一,该定位方法具有稳定性强、速度快的优点。由于速度模型假设为均匀或水平均匀介质,与实际介质有较大偏差,因此定位精度较低,特别是震源深度。为克服传统交切法的缺点,我们对其进行了改进。在改进的方法中,震源轨迹不再假设为圆形或双曲线形,而是利用最小走时树射线追踪方法进行精确计算。数值模型计算表明,本文提出的改进方法,可用于复杂速度模型的地震定位。
The intersection method is one of the basic approaches for locating earthquakes and is not only robust but also efficient.However,its location accuracy is not high,especially for focal depth because the velocity model used for the conventional intersection method is based on homogeneous or laterally homogeneous media,which is too simple.In order to improve the accuracy,we have modified the existing intersection method,in the modified approach,the earthquake loci are not assumed to be circular or hyperbolic and calculation accuracy is improved using a minimum traveltime tree algorithm for tracing rays.The numerical model shows that the modified method can locate earthquakes in complex velocity models.
The intersection method is one of the basic approaches for locating earthquakes and is not only robust but also efficient.However,its location accuracy is not high,especially for focal depth because the velocity model used for the conventional intersection method is based on homogeneous or laterally homogeneous media,which is too simple.In order to improve the accuracy,we have modified the existing intersection method,in the modified approach,the earthquake loci are not assumed to be circular or hyperbolic and calculation accuracy is improved using a minimum traveltime tree algorithm for tracing rays.The numerical model shows that the modified method can locate earthquakes in complex velocity models.
引文
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Gajewski,D.,and Tessmer,E.,2005,Reverse modelling for seismic event characterization:Geophys.J.Int.,163,276 -284.
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Klime(?) L.,and Kvasni(?)ka,M.,1994,3-D network ray tracing:Geohys.J.Int.,116,726-738.
Moser,T.J.,1991,Shortest path calculation of seismic rays: Geophysics,56,59-67.
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Nakanishi,I.,and Yamaguchi,K.,1986,A numerical experiment on nonlinear image reconstruction from first- arrival times for two-dimensional island arc structure:J. Phys.Earth,34,195-201.
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Shearer,P.M.,1997,Improving local earthquake location using the L1 norm and waveform cross correlation: Application to the Whittier Narrows,California, aftershock sequence:J.Geophys.Res.,102,8269-8283.
Udias,A.,1999,Principles of seismology:Cambridge University Press.
Waldhauser,F.,and Ellsworth,W.L.,2000,A double- difference earthquake location algorithm:method and application to the Northern Hayward Fault,California: Bull.Seism.Soc.Am.,90,1353-1368.
Wang,H.,and Chang,X.,2000,3-D tracing method based on graphic structure:Chinese J.Geophys.(in Chinese), 43,534-541.
Zhang,Z.,Badal,J.,Li,Y.,Chen,Y.,Yang,L.,and Teng,J., 2005,Crust-upper mantle seismic wave velocity structure across southeastern China:Tectonophysics,395,137-157.
Zhang,Z.,and Klemperer,S.L.,2005,West-east variation in crustal thickness in northern Lhasa block,central Tibet, from deep seismic sounding data:J.Geophys,Res.,110 (B09403) doi:10.1029/2004JB003139.
Zhao,A.,and Zhang,Z.,2004,Fast calculation of converted wave traveltimes in 3-D complex media:Chinese J. Geophys.(in Chinese),47,702-707.
Zhao,A.,Zhang,Z.,and Peng,S.,2003,Fast ray tracing method for convened waves in complex media:Journal of China University of Mining & Technology(in Chinese),32,513-516.
Zhao,A.,Zhang,Z.,and Teng,J.,2004,Minimum traveltime tree algorithm for seismic ray tracing: improvement in efficiency:J.Geophys.Eng.,1,245- 251.
Zhao,A.,Zhang,Z.,Wang,G.,and Wang,H..2000,A new scheme for fast calculation of seismic traveltimes and ray paths in heterogeneous media:Acta Seismological Sinica, 13,166-173.
Dijkstra,E.W.,1959,A note on two problems in connection with graphs:Numer.Math.,1,269-271.
Gajewski,D.,and Tessmer,E.,2005,Reverse modelling for seismic event characterization:Geophys.J.Int.,163,276 -284.
Geiger,L.,1912,Probability method for the determination of earthquake epicenters from the arrival time only:Bull. St.Louis Univ.,8,60-71.
Klime(?) L.,and Kvasni(?)ka,M.,1994,3-D network ray tracing:Geohys.J.Int.,116,726-738.
Moser,T.J.,1991,Shortest path calculation of seismic rays: Geophysics,56,59-67.
Moser,T.J.,van Eck,T.,and Nolet,G.,1992,Hypocenter determination in strongly heterogeneous earth models using shortest path method:J.Geophys.Res..97,6563- 6572.
Nakanishi,I.,and Yamaguchi,K.,1986,A numerical experiment on nonlinear image reconstruction from first- arrival times for two-dimensional island arc structure:J. Phys.Earth,34,195-201.
Pujol,J.,2004,Earthquake location tutorial:graphical approach and approximate epicentral location techniques: Seis.Res,Letter,75,63-74.
Shearer,P.M.,1997,Improving local earthquake location using the L1 norm and waveform cross correlation: Application to the Whittier Narrows,California, aftershock sequence:J.Geophys.Res.,102,8269-8283.
Udias,A.,1999,Principles of seismology:Cambridge University Press.
Waldhauser,F.,and Ellsworth,W.L.,2000,A double- difference earthquake location algorithm:method and application to the Northern Hayward Fault,California: Bull.Seism.Soc.Am.,90,1353-1368.
Wang,H.,and Chang,X.,2000,3-D tracing method based on graphic structure:Chinese J.Geophys.(in Chinese), 43,534-541.
Zhang,Z.,Badal,J.,Li,Y.,Chen,Y.,Yang,L.,and Teng,J., 2005,Crust-upper mantle seismic wave velocity structure across southeastern China:Tectonophysics,395,137-157.
Zhang,Z.,and Klemperer,S.L.,2005,West-east variation in crustal thickness in northern Lhasa block,central Tibet, from deep seismic sounding data:J.Geophys,Res.,110 (B09403) doi:10.1029/2004JB003139.
Zhao,A.,and Zhang,Z.,2004,Fast calculation of converted wave traveltimes in 3-D complex media:Chinese J. Geophys.(in Chinese),47,702-707.
Zhao,A.,Zhang,Z.,and Peng,S.,2003,Fast ray tracing method for convened waves in complex media:Journal of China University of Mining & Technology(in Chinese),32,513-516.
Zhao,A.,Zhang,Z.,and Teng,J.,2004,Minimum traveltime tree algorithm for seismic ray tracing: improvement in efficiency:J.Geophys.Eng.,1,245- 251.
Zhao,A.,Zhang,Z.,Wang,G.,and Wang,H..2000,A new scheme for fast calculation of seismic traveltimes and ray paths in heterogeneous media:Acta Seismological Sinica, 13,166-173.
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