2003年8月16日赤峰地震:一个可能发生在下地壳的地震?
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摘要
利用宽频带远震数字地震记录,计算赤峰台下方接收函数,得到了MOHO面深度为34～35km,并结合CRUST2.0模型等前人工作成果得到了赤峰地区的速度结构.我们以此速度结构作为模型,利用中国国家地震台网(CDSN)5个台站的宽频带地震数据,采用CAP方法反演2003年8月16日赤峰地震震源机制解并初步确定震源深度;再利用IRIS9个台站远震体波数据,通过对比理论计算和观测记录的方法进一步精确确定震源深度并验证反演得到的机制解,得出此次地震矩震级为5.2,震源机制解为:节面I:315°/64°/19°,节面II:216°/74°/152°,震源深度为25±2km,已深达下地壳.本文初步讨论了这样的发震深度所对应的可能发震机理和岩石物理特征,认为赤峰地区的下地壳处于相对低温的状态.
We used broadband teleseismic data of Chifeng station to calculate the Receiver Functions,then obtained a velocity model with H-K stacking method in combination with CRUST2.0 and other previous work.With this velocity model and broadband records from 5 CDSN stations,we inverted focal mechanisms of Chifeng earthquake on August 16th,2003 with the "Cut and Paste"(CAP)method.Then we confirmed focal depth and the source mechanisms by comparing synthetic body waves at teleseismic distance with broadband records of 9 IRIS stations.Our result shows that the best double couple solution of this Mw5.2 event is 315°,64° and 19°for strike,dip and slip angles respectively,the second nodal plane solution is 216°,74°,and 152°.The focal depth is 25±2 km,suggesting that this quake occurred in the lower crust which is much deeper than most continental earthquakes.This lower crust earthquake requires that the rock should be colder than expected.We proposed generation mechanism of this deep earthquake and its implications in rock strength and thermal state.
We used broadband teleseismic data of Chifeng station to calculate the Receiver Functions,then obtained a velocity model with H-K stacking method in combination with CRUST2.0 and other previous work.With this velocity model and broadband records from 5 CDSN stations,we inverted focal mechanisms of Chifeng earthquake on August 16th,2003 with the "Cut and Paste"(CAP)method.Then we confirmed focal depth and the source mechanisms by comparing synthetic body waves at teleseismic distance with broadband records of 9 IRIS stations.Our result shows that the best double couple solution of this Mw5.2 event is 315°,64° and 19°for strike,dip and slip angles respectively,the second nodal plane solution is 216°,74°,and 152°.The focal depth is 25±2 km,suggesting that this quake occurred in the lower crust which is much deeper than most continental earthquakes.This lower crust earthquake requires that the rock should be colder than expected.We proposed generation mechanism of this deep earthquake and its implications in rock strength and thermal state.
引文
[1]内蒙古自治区地震局.内蒙古自治区2003年和2004年两次5.9级地震.北京:地震出版社,2005.3～7Earthquake Administration of Inner Mongolia.TwoM5.9Earthquakes in Inner Mongolia between2003and2004(in Chinese).Beijing:Seismological Press,2005.3～7
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[10]Takeo M.An inversion method to analyze the rupture processes of earthquakes using near-field seismogram.Bull.Seism.Soc.Amer.,1987,77:490～513
[11]Sileny J,Panza G F.Inversion of seismograms to determine simultaneously the moment tensor components and source time functionfor a point source buriedin a horizontallylayered medium.Studia.Geophys.Geod.,1991,35:166～183
[12]Douglas A.Joint epicenter determination.Nature,1967,215:45～48
[13]Spence W.Relative epicenter determination using P-wave arrival-time differences.Bull.Seism.Soc.Amer.,1980,70(1):171～183
[14]Romney C.Seismic waves form the Dixie Valley Fairvjew Peak earthquakes.Bull.Seism.Soc.Amer.,1957,47(4):301～319
[15]Waldhanser F,Ellsworth W L.A double-difference earthquake location algorithm:method and application to the Northern Hayward Fault California.Bull.Seism.Soc.Amer.,2000,90(6):1353～1368
[16]Engdahl E R,Van der Hilst Rob,Buland Raymond.Global teleseismic earthquake relocation with improved travel times and procedures for depth determination.Bull.Seism.Soc.Amer.,1998,88(3):722～743
[17]Scholz C H.The Mechanics of Earthquakes and Faulting.Cambridge:Cambridge University Press,1990.145～155
[18]高孟潭,许力生,郭文生等.2003年8月16日内蒙古MS5.9地震震害分布特征及其成因分析.地震学报,2005,27(2):205～211Gao M T,Xu L S,Guo W S,et al.Spatial damage distribution of August16,2003,Inner Mongolia,China,MS=5.9earthquake and analysis.Acta Seismologica Sinica(in Chinese),2005,27(2):722～743
[19]Zhao L S,Hel mberger D V.Source estimation from broadband regional seismograms.Bull.Seis.Soc.Amer.,1994,84(1):91～104
[20]Zhu L P,Hel mberger D V.Advancement in source estimation techniques using broadband regional seismograms.Bull.Seis.Soc.Amer.,1996,86(5):1634～1641
[21]Kikuchi M,Kanamori H.Inversion of complex body waves—I.Bull.Seism.Soc.Amer.,1982,72(2):491～506
[22]Langston C A,Hel mberger D V.A procedure for modeling shallow dislocation sources.Geophys.J.R.astr.Soc.,1975,42:117～130
[23]Zhu L P,Rivera Luis A.A note on the dynamic and static displacements from a point source in multilayered media.Geophys.J.Int.,2002,148:619～627
[24]Zhu L P,Kanamori H.Moho depth variation in southern California from teleseismic receiver functions.J.Geophys.Res.,2000,105:2969～2980
[25]Bassin C,Laske G,Masters T G.The current limits of resolution for surface wave tomography in North America.EOS Trans AGU,2000,81:F897
[26]国家地震局《深部物探成果》编写组.中国地壳上地幔地球物理探测成果.北京:地震出版社,1986.206～2141986Chinese Seismological Bureau.Results of Geophysical Investigation in Chinese Crust and Mantle(in Chinese).Beijing:Seismological Press,1986.206～214
[27]Lay T,Wallace T C.Modern Global Seismology.Academic Press,1995.104～115
[28]Saikia C K.Modeling of the21May1997Jabalpur earthquake in central India:source parameters and regional path calibration.Bull.Seism.Soc.Amer.,2006,96:1396～1421
[29]Liu Q,Polet J,Komatitsch D,et al.Spectral-element moment-tensor inversions for earthquakes in southern California.Bull.Seism.Soc.Amer.,2004,94(5):1748～1761
[30]Yang W.Heat flow pattern and lateral variations of lithosphere strengthin China mainland:constraints on active deformation.Phys.Earth Planet.Interiors,2001,126:121～146
[2]张国民,汪素云,李丽等.中国大陆地震震源深度及其构造含义.科学通报,2002,47(9):663～668Zhang G M,Wang S Y,Li L,et al.Focal depth research of earthquakes in mainland China:implication for tectonics.Chinese Science Bulletin(in Chinese),2002,47(9):663～668
[3]石耀霖,朱守彪.中国震源机制深度变化反映的地壳-地幔流变特征.地球物理学报,2003,46(3):395～365Shi Y L,Zhu S B.Contrast of rheology in the crust and mantle near Moho revealed by depth variation of earthquake mechanismin continental China.Chinese J.Geophys.(in Chinese),2003,46(3):395～365
[4]Kanamori H,Given J W.Use of long period surface waves for rapid determination of the earthquake source parameters.Phys.Earth Planet.Interiors,1981,27:8～31
[5]Thio H K,Kanamori H.Moment-tensor inversions for local earthquakes using surface waves recorded at TERRAscope.Bull.Seis.Soc.Amer.,1995,85:1021～1038
[6]马淑田,姚振兴,纪晨,1996年5月3日内蒙古包头西MS6.4级地震的震源机制研究.地球物理学报,1998,41(6):795～804Ma S T,Yao Z X,Ji C.Astudyfor the mechanismofMS6.4earthquake on May3,1996at west Bao Tou,Nei Mongol.Chinese J.Geophys.(in Chinese),1998,41(6):795～804
[7]许力生,陈运泰.从全球长周期波形资料反演2001年11月14日昆仑山口地震时空破裂过程.中国科学D辑,2004,34(3):256～264Xu L S,Chen Y T.Temporal and spatial rupture process of the November14,2001Kunlun Mountain great earthquake fromthe GDSNlong period waveformdata.Sciencein China Series D(in Chinese),2004,34(3):256～264
[8]Dziewonski A M,Chou T A,Woodhouse J H.Determination of earthquake source parameters from waveform data for studies of global and regional seismicity.J.Geophys.Res.,1981,86:2825～2852
[9]Dreger D S,Hel mberger D V.Determination of source parameters at regional distances with three-component sparse network data.J.Geophys.Res.,1993,98:8107～8125
[10]Takeo M.An inversion method to analyze the rupture processes of earthquakes using near-field seismogram.Bull.Seism.Soc.Amer.,1987,77:490～513
[11]Sileny J,Panza G F.Inversion of seismograms to determine simultaneously the moment tensor components and source time functionfor a point source buriedin a horizontallylayered medium.Studia.Geophys.Geod.,1991,35:166～183
[12]Douglas A.Joint epicenter determination.Nature,1967,215:45～48
[13]Spence W.Relative epicenter determination using P-wave arrival-time differences.Bull.Seism.Soc.Amer.,1980,70(1):171～183
[14]Romney C.Seismic waves form the Dixie Valley Fairvjew Peak earthquakes.Bull.Seism.Soc.Amer.,1957,47(4):301～319
[15]Waldhanser F,Ellsworth W L.A double-difference earthquake location algorithm:method and application to the Northern Hayward Fault California.Bull.Seism.Soc.Amer.,2000,90(6):1353～1368
[16]Engdahl E R,Van der Hilst Rob,Buland Raymond.Global teleseismic earthquake relocation with improved travel times and procedures for depth determination.Bull.Seism.Soc.Amer.,1998,88(3):722～743
[17]Scholz C H.The Mechanics of Earthquakes and Faulting.Cambridge:Cambridge University Press,1990.145～155
[18]高孟潭,许力生,郭文生等.2003年8月16日内蒙古MS5.9地震震害分布特征及其成因分析.地震学报,2005,27(2):205～211Gao M T,Xu L S,Guo W S,et al.Spatial damage distribution of August16,2003,Inner Mongolia,China,MS=5.9earthquake and analysis.Acta Seismologica Sinica(in Chinese),2005,27(2):722～743
[19]Zhao L S,Hel mberger D V.Source estimation from broadband regional seismograms.Bull.Seis.Soc.Amer.,1994,84(1):91～104
[20]Zhu L P,Hel mberger D V.Advancement in source estimation techniques using broadband regional seismograms.Bull.Seis.Soc.Amer.,1996,86(5):1634～1641
[21]Kikuchi M,Kanamori H.Inversion of complex body waves—I.Bull.Seism.Soc.Amer.,1982,72(2):491～506
[22]Langston C A,Hel mberger D V.A procedure for modeling shallow dislocation sources.Geophys.J.R.astr.Soc.,1975,42:117～130
[23]Zhu L P,Rivera Luis A.A note on the dynamic and static displacements from a point source in multilayered media.Geophys.J.Int.,2002,148:619～627
[24]Zhu L P,Kanamori H.Moho depth variation in southern California from teleseismic receiver functions.J.Geophys.Res.,2000,105:2969～2980
[25]Bassin C,Laske G,Masters T G.The current limits of resolution for surface wave tomography in North America.EOS Trans AGU,2000,81:F897
[26]国家地震局《深部物探成果》编写组.中国地壳上地幔地球物理探测成果.北京:地震出版社,1986.206～2141986Chinese Seismological Bureau.Results of Geophysical Investigation in Chinese Crust and Mantle(in Chinese).Beijing:Seismological Press,1986.206～214
[27]Lay T,Wallace T C.Modern Global Seismology.Academic Press,1995.104～115
[28]Saikia C K.Modeling of the21May1997Jabalpur earthquake in central India:source parameters and regional path calibration.Bull.Seism.Soc.Amer.,2006,96:1396～1421
[29]Liu Q,Polet J,Komatitsch D,et al.Spectral-element moment-tensor inversions for earthquakes in southern California.Bull.Seism.Soc.Amer.,2004,94(5):1748～1761
[30]Yang W.Heat flow pattern and lateral variations of lithosphere strengthin China mainland:constraints on active deformation.Phys.Earth Planet.Interiors,2001,126:121～146
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