利用尾波包络线反演方法研究伽师强震群区地壳的非均匀结构
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摘要
以单次散射模型、球形辐射源、一维线性速度模型为基础计算理论包络线,通过尾波归一化方法把理论与观测包络线结合起来形成非线性方程组,用迭代最小二乘方法反演伽师强震群区的散射系数空间分布.结果表明,伽师强震群区下方中上地壳中存在明显的非均匀结构.在10～25km各深度图像上,研究区中部都存在一低散射系数区,这个低散射系数区在10km、15km深度被高散射系数区包围,在20km深度仅其东侧存在高散射系数区.1997年的7次Ms≥6.0级地震发生在研究区中部的低散射系数区内或低散射系数区向高散射系数区过渡带的低散射系数一侧.
Synthetic envelopes are calculated on the basis of the single scattering theory,assuming spherical radiation sources and a one-dimensional depth-dependent velocity structure.An observation equation,which connects synthetic and observed energy densities,is obtained employing coda normalization method.Finally,we obtain the spatial distribution of scattering coefficient of Jiashi strong earthquake swarm region using a standard least squares technique iteratively.The results show that the structure is obviously inhomogeneous in the middle and upper crust.A low scattering coefficient zone exists at depth of 10~25 km in the central part of research area.This low scattering coefficient zone is surrounded by large scattering coefficient zones at depth of 10 km and 15 km,but the large scattering coefficient zone remains only in the east at depth 20 km.Seven Ms≥6.0 earthquakes in 1997 occurred at the center or edge of the low scattering coefficient zone.
Synthetic envelopes are calculated on the basis of the single scattering theory,assuming spherical radiation sources and a one-dimensional depth-dependent velocity structure.An observation equation,which connects synthetic and observed energy densities,is obtained employing coda normalization method.Finally,we obtain the spatial distribution of scattering coefficient of Jiashi strong earthquake swarm region using a standard least squares technique iteratively.The results show that the structure is obviously inhomogeneous in the middle and upper crust.A low scattering coefficient zone exists at depth of 10~25 km in the central part of research area.This low scattering coefficient zone is surrounded by large scattering coefficient zones at depth of 10 km and 15 km,but the large scattering coefficient zone remains only in the east at depth 20 km.Seven Ms≥6.0 earthquakes in 1997 occurred at the center or edge of the low scattering coefficient zone.
引文
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[2]Aki K,Chouet B.Origin of coda waves:Source,attenuation and scattering effects.J.Geophys.Res.,1975,80:3322～3342
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[18]Menke W.Geophysical Data Analysis:Discrete Inverse Theory.Academic,San Diego,Calif.,1984
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[20]徐锡伟,张先康,冉勇康等.南天山地区巴楚—伽师地震(Ms6.8)发震构造初步研究.地震地质,2006,28(2):161～178Xu X W,Zhang X K,Ran Y K,et al.The preliminary study on seismotectonics of the2003Bachu-Jiashi earthquake(Ms6.8),southern Tianshan.Seismology and Geology(in Chinese),2006,28(2):161～178
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[23]刘启元,陈九辉,李顺成等.新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨.地球物理学报,2000,43(3):356～365Liu Q Y,Chen J H,Li S C,et al.Passive seismic experiment in Xingjiang-Jiashi strong earthquake region and discussion on its seismic genesis.Chinese J.Geophys.(in Chinese),2000,43(3):356～365
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[25]郭飙,刘启元,陈九辉等.新疆伽师强震区余震序列的地震台阵定位.地震地质,2002,24(2):199～207Gguo B,Liu Q Y,Chen J H,et al.Relocation of earthquake sequences using joint hypocenter determination method:portable seismic array study in Jiashi region,Xinjiang.Seismologyand Geology(in Chinese),2002,24(2):199～207
[26]Sato H,Fehler M.Seismic Wave Propagation and Scattering in the Heterogeneous Earth.Springer-Verlag,New York,1998
[27]Zhao D,Hasegawa A,Horiuchi S.Tomographic imaging of P and S wave velocity structure beneath northeastern Japan.J.Geophys.Res.,1992,97:19909～19928
[28]杨卓欣,赵金仁,张先康.伽师强震群区上地壳三维速度层析成像.地震学报,2002,24(2):153～161Yang Z X,Zhao J R,Zhang X K.3-Dvelocitytomographyin the upper crust in the epicenter of the Jiashi strong earthquake swarm.Acta Seismologica Sinica(in Chinese),2002,24(2):153～161
[29]李松林,张先康,Mooney W,等.伽师地震区地壳细结构及发震断层的初步研究.地球物理学报,2002,45(1):75～82Li S L,Zhang X K,Mooney W D,et al.A preliminary study on fine structures of Jiashi earthquake region and earthquake generation fault.Chinese J.Geophys.(in Chinese),2002,45(1):76～82
[30]梅世蓉.地震前兆场物理模式与前兆时空分布机制研究(一)—坚固体孕震模式的由来与证据.地震学报,1995,17(3):273～282Mei S R.On the physical model of earthquake precursor fields and the mechanism of precursor time-space distribution:Origin and evidence of the strong body earthquake-generating model.Acta Seismologica Sinica(in Chinese),1995,17(3):273～282
[2]Aki K,Chouet B.Origin of coda waves:Source,attenuation and scattering effects.J.Geophys.Res.,1975,80:3322～3342
[3]Sato H.Energy propagation including scattering effects single isotropic scattering approximation.J.Phys.Earth,1977,25:27～41
[4]Singh S,Herrmann R B.Regionalization of crustal codaQin the continental United States.J.Geophys.Res.,1983,88:527～238
[5]Sato H.Meanfree path of S-wave under the Kanto district of Japan.J.Phys.Earth,1978,26:185～198
[6]Aki K.Scattering and attenuating of shear waves in the lithosphere.J.Geophys.Res.,1980,85:6496～6504
[7]Neidell N,Taner M.Semblance and other coherency measures for multichannel data.Geophysics,1971,36:482～497
[8]Gupta I,Lynnes C,Wagner R,et al.BroadbandF-K analysis of array data to identify sources of local scattering.Geophys.Res.Lett.,1990,17:183～186
[9]Matsumoto S,Obara K,Hasegawa A,et al.Imaging P-wave scatterer distribution in the focal area of the1995M7.2Hyogo-ken Nanbu(Kobe)Earthquakes.Geophys.Res.Lett.,1998,25:1439～1442
[10]Revenaugh J.Ascattered-wave image of subduction beneath the Transverse Range.Science,1995,268:1888～1892
[11]Revenaugh J.The relation of crustal scattering to seismisity in southern California.J.Geophys.Res.,2000,105:25403～25422
[12]Taira T,Yomogida K,Kuwahara Y,et al.Imaging of smallscale crustal heterogeneity as seismic scatterers with array data II:Application of the Nagamachi-Rifu fault area,Japan.J.Geophys.Res.,2007,112:B06312
[13]Nishigami K.Deep structure heterogeneity along and around the San Andreas fault system in central California and its relation to the segmentation.J.Geophys.Res.,2000,105:7983～7998
[14]Asano Y,Hasegawa A.Imaging the fault zones of the2000western Tottori earthquake by a new inversion method to estimate three-dimensional distribution of the scattering coefficient.J.Geophys.Res.,2004,109:B06306,doi:10.1029/2003JB002761
[15]Asano Y,Obara K,Nakajima J,et al.Inhomogeneous crustal structure beneath northern Miyagi prefecture,northeastern Japan,imaged by coda envelope inversion:Implication for fluid distribution.Geophys.Res.Lett.,2004,31:L24615
[16]Obara K.Simulations of anomalous seismogramenvelopes at coda portions.Phys.Earth Planet.Inter.,1997,104:109～125
[17]Aki K.Attenuation of shear-waves in the lithosphere for frequencies from0.05to25Hz.Phys.Earth Planet.Inter.,1980,21:50～60
[18]Menke W.Geophysical Data Analysis:Discrete Inverse Theory.Academic,San Diego,Calif.,1984
[19]徐朝繁,张先康,段永红等.新疆伽师强震群区上部地壳细结构的高分辨折射地震探测研究.地震学报,2006,28(1):60～69Xu Z F,Zhang X K,Duan Y H,et al.Fine upper crustal structure of Jiashi strong earthquake swarm region in Xinjiang inferred from high resolution seismic refraction profile data.Acta Seismologica Sinica(in Chinese),2006,28(1):60～69
[20]徐锡伟,张先康,冉勇康等.南天山地区巴楚—伽师地震(Ms6.8)发震构造初步研究.地震地质,2006,28(2):161～178Xu X W,Zhang X K,Ran Y K,et al.The preliminary study on seismotectonics of the2003Bachu-Jiashi earthquake(Ms6.8),southern Tianshan.Seismology and Geology(in Chinese),2006,28(2):161～178
[21]赵翠萍.1997—2003年伽师震源区特征的地震学方法研究[博士论文].北京:中国地震局地球物理研究所,2006Zhao C P.Seismological studies on the characteristics of Jiashi source region from1997to2003[Ph.D.thesis].Beijing:Institute of Geophysics,China Earthquake Administration,2006
[22]周仕勇,许忠淮,韩京等.主地震定位法分析以及1997年新疆伽师强震群高精度定位.地震学报,1999,21(3):258～265Zhou S Y,Xu Z H,Han J,et al.Analysis on the master event method and precise location of1997Jiashi strong earthquake swarm in western China.Acta Seismologica Sinica(in Chinese),1999,12(3):258～265
[23]刘启元,陈九辉,李顺成等.新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨.地球物理学报,2000,43(3):356～365Liu Q Y,Chen J H,Li S C,et al.Passive seismic experiment in Xingjiang-Jiashi strong earthquake region and discussion on its seismic genesis.Chinese J.Geophys.(in Chinese),2000,43(3):356～365
[24]张先康,赵金仁,张成科等.帕米尔东北侧地壳结构研究.地球物理学报,2002,45(5):665～671Zhang X K,Zhao J R,Zhang C K,et al.Crustal structure at the Northeast side of the Pamirs.Chinese J.Geophys.,(in Chinese),2002,45(5):665～671
[25]郭飙,刘启元,陈九辉等.新疆伽师强震区余震序列的地震台阵定位.地震地质,2002,24(2):199～207Gguo B,Liu Q Y,Chen J H,et al.Relocation of earthquake sequences using joint hypocenter determination method:portable seismic array study in Jiashi region,Xinjiang.Seismologyand Geology(in Chinese),2002,24(2):199～207
[26]Sato H,Fehler M.Seismic Wave Propagation and Scattering in the Heterogeneous Earth.Springer-Verlag,New York,1998
[27]Zhao D,Hasegawa A,Horiuchi S.Tomographic imaging of P and S wave velocity structure beneath northeastern Japan.J.Geophys.Res.,1992,97:19909～19928
[28]杨卓欣,赵金仁,张先康.伽师强震群区上地壳三维速度层析成像.地震学报,2002,24(2):153～161Yang Z X,Zhao J R,Zhang X K.3-Dvelocitytomographyin the upper crust in the epicenter of the Jiashi strong earthquake swarm.Acta Seismologica Sinica(in Chinese),2002,24(2):153～161
[29]李松林,张先康,Mooney W,等.伽师地震区地壳细结构及发震断层的初步研究.地球物理学报,2002,45(1):75～82Li S L,Zhang X K,Mooney W D,et al.A preliminary study on fine structures of Jiashi earthquake region and earthquake generation fault.Chinese J.Geophys.(in Chinese),2002,45(1):76～82
[30]梅世蓉.地震前兆场物理模式与前兆时空分布机制研究(一)—坚固体孕震模式的由来与证据.地震学报,1995,17(3):273～282Mei S R.On the physical model of earthquake precursor fields and the mechanism of precursor time-space distribution:Origin and evidence of the strong body earthquake-generating model.Acta Seismologica Sinica(in Chinese),1995,17(3):273～282
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