鄂尔多斯块体Lg尾波衰减及其分布图像
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摘要
利用32个地震台站记录到的19次地震事件共487条垂直方向数字化波形记录,采用单台记录叠加频谱比法(SSR法)计算得到了每条地震记录在0.6～10Hz范围内共51个频率点的Lg尾波Q值,并统计得到了鄂尔多斯块体Lg尾波衰减的频率依赖关系.同时,利用遗传算法计算得到了鄂尔多斯块体Lg尾波在频率为1Hz处的衰减(Q0)值、频率依赖指数(η)值的空间分布,并计算了其误差的空间分布,讨论了成像分辨率.结果表明,鄂尔多斯块体虽然是一个稳定构造地区,但其Lg尾波Q0值低于加拿大地盾、西伯利亚地台的Q0值,其η值大于加拿大地盾、西伯利亚地台的结果,且其Q0值、η值具有横向不均匀性的特征.Q0值的空间分布与地震活动、地热流值分布具有较好的一致性.
The quality factor of Lg coda wave beneath Ordos massif is evaluated by using the stacked spectral ratio method.The measurement is made from Lg wave records of 19 earthquakes at 32 vertical seismic stations of the Shanxi seismic network,Shaanxi seismic network and Ningxia seismic network.Q has been calculated for a set of 51 frequencies between 0.6Hz and 10Hz for each seismic record and has been found to be a relation between Q value and frequency.The images of the quality factor at 1.0Hz(Q0)and the frequency index(η)have been calculated,by using the genetic algorithm.Although they are all in stable regions,the Ordos show high attenuation moreover Canadian shield and Siberian platform show low attenuation.The tomographic patterns of Q0 correlate well with those of the level of seismic activity and the heat flow field in the Ordos massif.
The quality factor of Lg coda wave beneath Ordos massif is evaluated by using the stacked spectral ratio method.The measurement is made from Lg wave records of 19 earthquakes at 32 vertical seismic stations of the Shanxi seismic network,Shaanxi seismic network and Ningxia seismic network.Q has been calculated for a set of 51 frequencies between 0.6Hz and 10Hz for each seismic record and has been found to be a relation between Q value and frequency.The images of the quality factor at 1.0Hz(Q0)and the frequency index(η)have been calculated,by using the genetic algorithm.Although they are all in stable regions,the Ordos show high attenuation moreover Canadian shield and Siberian platform show low attenuation.The tomographic patterns of Q0 correlate well with those of the level of seismic activity and the heat flow field in the Ordos massif.
引文
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[2]Herrmann R B,Kijko A.Modeling some empirical Lg rela-tions[J].Bull SeismSoc Am,1983,56:257～272.
[3]Wang C Y,Herrmann R B.Synthesis of coda wavesinlayered medium[J].Pure Appl Geophys,1988,128:7～42.
[4]Zhang T,Lay T.Why the Lg phase does not traverse oceanic crust[J].Bull Seismol Soc Am,1995,85:1665～1678.
[5]Aki K.Analysis of the seismic coda of local earthquakes as scattered waves[J].J Geophys Res,1969,74:615～631.
[6]Suteau A M,Whitcomb J H.Alocal earthquake coda magni-tude andits relation to duration,moment M0andlocal magni-tude ML[J].Bull SeismSoc Am,1979,69:353～368.
[7]Herrmann R B.Qestimates using coda of local earthquakes[J].Bull SeismSoc Am,1980,70:447～469.
[8]Xie J,Nuttli O W.Interpretation of high-frequency coda at large distances:stochastic modeling and method of inversion[J].Geophysical Journal,1988,95:579～595.
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[14]Mitchell B J,Pan Y,Xie J,et al.Lg codaQvariation across Eurasia and its relation to crustal evolution[J].J Geophys Res,1997,102:22767～22779.
[15]秦家政,阚荣举.用近震尾波估算昆明及周围地区的Q值及地震矩[J].地球物理学报,1986,29(2):145～155.Qin J Z,Kan RJ.Estimate theQvalue and moments by using near earthquakes coda in the KunMing and its adjacent re-gions[J].Chinese J.Geophys.(in Chinese),1986,29(2):145～155.
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[17]刘建华,刘福田,阎晓蔚,等.华北地区Lg尾波衰减研究—Lg尾波Q0地震成像[J].地球物理学报,2004,47(6):1044～1052.Liu J H,Liu F T,Yan X W,et al.Astudy of Lg coda at-tenuation beneath North China:seismic imaging Lg codaQ0[J].Chinese J.Geophys.(in Chinese),2004,47(6):1044～1052.
[18]范福田.大地构造轮廓和新构造运动[A].见:国家地震局鄂尔多斯周缘活动断裂系课题组编.鄂尔多斯周缘活动断裂系[C].北京:地震出版社,1988,5～19.Fan F T.Geotectonic framework and neotectonism[A].The research group on“active fault system around Ordos Mas-sif”,State Seismological Bureau,Active fault system around Ordos Massif(in Chinese)[C].Beijing:Seismological Press,1988,5～19.
[19]刘红桂,啜永清,陈书清,等.鄂尔多斯地块地壳内S波衰减特征的研究[J].地震学报,2005,27(5):488～497.Liu H G,Chuo Y Q,Chen S Q,et al.Attenuation of S wave in the crust of Ordos massif[J].ACTA Seismologica Sinica,2005,18(5):521～531.
[20]Michel C,Jean-Louis P,Michel B.Frequency-dependent at-tenuation in the crust beneath central France form Lg waves:data analysis and numerical modeling[J].Bull Seism Soc A-mer,1985,75:1395～1411.
[21]Chael E.Spectral scaling of earthquakes in the Miramichi re-gion of New Brunswick[J].Bull SeismSoc Amer,1987,77:347～365.
[22]刘红桂,缪发军,吴晶.场地响应、震源参数与介质衰减的同时反演[J].地震,2004,24(4):27～36.Liu H G,Miao F J,Wu J.Simultaneous inversion of site re-sponse,source parameters,geometrical attenuation factors andinelasticcoeff icient of medium[J].Earthquake(in Chi-nese),2004,24(4):27～36.
[23]Humphreys E,Clayton R W.Adaptation of back projection tomography to seismic travel time problems[J].J Geophys Res,1988,93:1073～1086.
[24]Baqer S,Mitchell BJ.Regional variations of Lg codaQinthe continental United States andits relation to crustal structure and evolution[J].Pure Appl Geophys,1998,158:613～638.
[25]Hasegawa H S.Attenuation of Lg waves in the Canadian shield[J].Bull SeismSoc Amer.1985,75(6):1569～1582.
[26]Nuttli O W.Lg magnitudes and yield estimates for under-ground Novaya Zemlya nuclear explosions[J].Bull SeismSoc Am,1988,78:873～884.
[27]李清林,栗文山,张晓普,等.鄂尔多斯及其周缘地热分布的某些特征[J].西北地震学报.1996,18(2):51～59.Li Q L,Li WS,Zhang X P,et al.Characteristics of geother-mal distributionin Ordos and its vicinity[J].Northwestern seismological journal(in Chinese),1996,18(2):51～59.
[28]Mitchell B J.Anelastic structure and evolution of the conti-nental crust and upper mantle fromseismic surface wave at-tenuation[J].Rev Geophys,1995,33:441～462.
[2]Herrmann R B,Kijko A.Modeling some empirical Lg rela-tions[J].Bull SeismSoc Am,1983,56:257～272.
[3]Wang C Y,Herrmann R B.Synthesis of coda wavesinlayered medium[J].Pure Appl Geophys,1988,128:7～42.
[4]Zhang T,Lay T.Why the Lg phase does not traverse oceanic crust[J].Bull Seismol Soc Am,1995,85:1665～1678.
[5]Aki K.Analysis of the seismic coda of local earthquakes as scattered waves[J].J Geophys Res,1969,74:615～631.
[6]Suteau A M,Whitcomb J H.Alocal earthquake coda magni-tude andits relation to duration,moment M0andlocal magni-tude ML[J].Bull SeismSoc Am,1979,69:353～368.
[7]Herrmann R B.Qestimates using coda of local earthquakes[J].Bull SeismSoc Am,1980,70:447～469.
[8]Xie J,Nuttli O W.Interpretation of high-frequency coda at large distances:stochastic modeling and method of inversion[J].Geophysical Journal,1988,95:579～595.
[9]刘建华,刘福田,王凤霞,等.单台Lg尾波QCLg的测量研究[J].地球物理学报,1999,42(3):371～382.Liu J H,Liu F T,Wang F X,et al.A measuring study for single-trace Lg codaQCLg[J].Chinese J.Geophys.(in Chi-nese),1999,42(3):371～382.
[10]Xie J,Mitchell B R.A back-projection method for imaging large-scale lateral variations of Lg codaQwith application to continental Africa[J].Geophys J Int,1990,100:161～181.
[11]De Souza J L,Mitchell B J.Lg codaQvariations across South America and their relation to crustal evolution[J].Pure Appl Geophys,1998,158:587～612.
[12]Cong L,Mitchell BJ.Lg codaQandits relation to the Geol-ogy and tectonics of the Middle East[J].Pure Appl Geo-phys,1998,158:563～585.
[13]Mitchell B J,Baqer S,Akinci A,et al.Lg codaQin Aus-tralia and its relation to crustal structure and evolution[J].Pure Appl Geophys,1998,158:639～653.
[14]Mitchell B J,Pan Y,Xie J,et al.Lg codaQvariation across Eurasia and its relation to crustal evolution[J].J Geophys Res,1997,102:22767～22779.
[15]秦家政,阚荣举.用近震尾波估算昆明及周围地区的Q值及地震矩[J].地球物理学报,1986,29(2):145～155.Qin J Z,Kan RJ.Estimate theQvalue and moments by using near earthquakes coda in the KunMing and its adjacent re-gions[J].Chinese J.Geophys.(in Chinese),1986,29(2):145～155.
[16]丛连理,胡家富,傅竹波,等.中国大陆及邻近地区Lg尾波的Q值分布[J].中国科学(D辑),2002,32(8):617～625.Cong L L,Hu J F,Fu Z B,et.al.Distribution of Lg codaQ in the Chinese continent and its adjacent regions[J].Science in China,Ser.D(in Chinese),2002,32(8):617～625.
[17]刘建华,刘福田,阎晓蔚,等.华北地区Lg尾波衰减研究—Lg尾波Q0地震成像[J].地球物理学报,2004,47(6):1044～1052.Liu J H,Liu F T,Yan X W,et al.Astudy of Lg coda at-tenuation beneath North China:seismic imaging Lg codaQ0[J].Chinese J.Geophys.(in Chinese),2004,47(6):1044～1052.
[18]范福田.大地构造轮廓和新构造运动[A].见:国家地震局鄂尔多斯周缘活动断裂系课题组编.鄂尔多斯周缘活动断裂系[C].北京:地震出版社,1988,5～19.Fan F T.Geotectonic framework and neotectonism[A].The research group on“active fault system around Ordos Mas-sif”,State Seismological Bureau,Active fault system around Ordos Massif(in Chinese)[C].Beijing:Seismological Press,1988,5～19.
[19]刘红桂,啜永清,陈书清,等.鄂尔多斯地块地壳内S波衰减特征的研究[J].地震学报,2005,27(5):488～497.Liu H G,Chuo Y Q,Chen S Q,et al.Attenuation of S wave in the crust of Ordos massif[J].ACTA Seismologica Sinica,2005,18(5):521～531.
[20]Michel C,Jean-Louis P,Michel B.Frequency-dependent at-tenuation in the crust beneath central France form Lg waves:data analysis and numerical modeling[J].Bull Seism Soc A-mer,1985,75:1395～1411.
[21]Chael E.Spectral scaling of earthquakes in the Miramichi re-gion of New Brunswick[J].Bull SeismSoc Amer,1987,77:347～365.
[22]刘红桂,缪发军,吴晶.场地响应、震源参数与介质衰减的同时反演[J].地震,2004,24(4):27～36.Liu H G,Miao F J,Wu J.Simultaneous inversion of site re-sponse,source parameters,geometrical attenuation factors andinelasticcoeff icient of medium[J].Earthquake(in Chi-nese),2004,24(4):27～36.
[23]Humphreys E,Clayton R W.Adaptation of back projection tomography to seismic travel time problems[J].J Geophys Res,1988,93:1073～1086.
[24]Baqer S,Mitchell BJ.Regional variations of Lg codaQinthe continental United States andits relation to crustal structure and evolution[J].Pure Appl Geophys,1998,158:613～638.
[25]Hasegawa H S.Attenuation of Lg waves in the Canadian shield[J].Bull SeismSoc Amer.1985,75(6):1569～1582.
[26]Nuttli O W.Lg magnitudes and yield estimates for under-ground Novaya Zemlya nuclear explosions[J].Bull SeismSoc Am,1988,78:873～884.
[27]李清林,栗文山,张晓普,等.鄂尔多斯及其周缘地热分布的某些特征[J].西北地震学报.1996,18(2):51～59.Li Q L,Li WS,Zhang X P,et al.Characteristics of geother-mal distributionin Ordos and its vicinity[J].Northwestern seismological journal(in Chinese),1996,18(2):51～59.
[28]Mitchell B J.Anelastic structure and evolution of the conti-nental crust and upper mantle fromseismic surface wave at-tenuation[J].Rev Geophys,1995,33:441～462.
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