日本上地壳S波衰减成像
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摘要
地球介质的衰减特性可以从地震波中的频谱信息中获取,并且能够提供地球内部结构非均匀性的重要信息.与大量的速度结构研究相比,对衰减结构的研究却较少,且大多仅对日本群岛局部地区做研究.本文运用ML振幅层析成像技术反演获得了整个日本群岛上地壳的品质因子Q0值(1Hz时的Q值).计算中共利用了日本Hi-net台网971个台站记录到的5559个地震事件,超过60000条Sg波最大振幅-频率数据,并且满足震中距小于2°、震源深度小于10km.计算结果表明,低Q0值区域主要存在于日本群岛的中央火山带,与日本新生代以来的火山分布非常一致;同时,位于从神户到京都东北地区、以及四国岛东部等地的非火山区,断层密集,对应的Q0值也很低;另外,西太平洋俯冲海沟与日本群岛东海岸之间的区域也是低Q0值区,这说明高温、岩石强烈破碎、深厚的沉积物是造成地震波强烈衰减的主要原因.高Q0值主要分布在中央火山带前缘与日本东海岸之间.
Seismic attenuation(Q-factor)can be estimated by extracting the amplitude-frequency information contained in seismic waveforms.We applied ML amplitude tomography to estimate attenuation of upper crust in Japan.More than 60000 Sg-wave maximum amplitude data from 5559 events recorded by 971 stations were selected from the dense High-Sensitivity Seismographic Network(Hi-net)under the condition that epicentral distance is less than 2°;event depth is less than 10km.The lateral S-wave Q-factor variations of upper crust at 1Hz in Japan were obtained,and the result indicates that the low Q values exist in the central Japan islands,and have almost the same distribution with volcanoes;the low-Q zones also exist in non-volcanic regions at the Kyoto and Kobe prefectures,and eastern Shikoku with dense faults there;in addition,low Q was found between eastern coast and Japan trench.These suggest that the high attenuation(low Q value)results from high temperature,cracked rocks and thick sediment.The high Q values mainly exist between the front of volcanoes and the Japanese east coast.
Seismic attenuation(Q-factor)can be estimated by extracting the amplitude-frequency information contained in seismic waveforms.We applied ML amplitude tomography to estimate attenuation of upper crust in Japan.More than 60000 Sg-wave maximum amplitude data from 5559 events recorded by 971 stations were selected from the dense High-Sensitivity Seismographic Network(Hi-net)under the condition that epicentral distance is less than 2°;event depth is less than 10km.The lateral S-wave Q-factor variations of upper crust at 1Hz in Japan were obtained,and the result indicates that the low Q values exist in the central Japan islands,and have almost the same distribution with volcanoes;the low-Q zones also exist in non-volcanic regions at the Kyoto and Kobe prefectures,and eastern Shikoku with dense faults there;in addition,low Q was found between eastern coast and Japan trench.These suggest that the high attenuation(low Q value)results from high temperature,cracked rocks and thick sediment.The high Q values mainly exist between the front of volcanoes and the Japanese east coast.
引文
[1]Mitchell B J.Anelastic structure and evolution of the conti-nental crust and upper mantle from seismic surface wave attenuation.Rev.Geophys.,1995,33:441～462
[2]Molas G L,Yamazaki F.Attenuation of earthquake ground motionin Japan including deep-focus events.Bulletin of the Seismological Society of America,1995,85(5):1343～1358
[3]Fukushima Y,Berce-Thierry C,Volant P,et al.Attenuation relation for west eurasia determined with recent near-fault records from California,Japan and Turkey.Journal of Earthquake Engineering,2003,7(4):573～598
[4]Mamada Y,Takenaka H.Strong attenuation of shear waves in the focal region of the1997Northwestern Kagoshima earthquakes,Japan.Bulletinofthe Seismological Society of America,2004,94(2):464～478
[5]Kanno T,Narita A,Morikawa N,et al.A newattenuation relation for strong ground motionin Japan based on recorded data.Bulletin of the Seismological Society of America,2006,96(3):879～897
[6]Zhao J X,Zhang J,Asano A,et al.Attenuation relations of strong ground motion in Japan using site classification based on predominant period.Bulletinofthe Seismological Society of America,2006,96(3):898～913
[7]Nakamura R,Satake K,Toda S,et al.Three-dimensional attenuation(Qs)structure beneaththe Kanto district,Japan,as inferredfromstrong motion records.Geophysical Research Letters,2006,33,L21304,doi:10.1029/2006GL027352
[8]Sekiguchi S.Three-dimensionalQstructure beneath the Kanto-Tokai district,Japan.Tectonophysics,1991,195:83～104
[9]Katsumata K,Urabe T,Mizoue M.Evidence for a seismic attenuation anomaly beneath the Hida mountain-range,Central Honshu,Japan.Geophysical Journal International,1995,120(2):237～246
[10]Tsumura N,Hasegawa A,Horiuchi S.Simultaneous estimation of attenuation structure,source parameters and site response spectra-Application to the northeastern part of Honshu,Japan.Physics of the Earth and Planetary Interiors,1996,93:105～121
[11]Yamamoto K,Ida Y.Significant P wave attenuation for aspecific frequency range beneath Kirishima Volcano,Japan.Geophysical Research Letters,1997,24(10):1275～1278
[12]Takanami T,Sacks I S,Hasegawa A.Attenuation structure beneath the volcanic front in northeastern Japan from broad-band seismograms.Physics of the Earth and Planetary Interiors,2000,121:339～357
[13]Tsumura N,Matsumoto S,Horiuchi S,et al.Three-dimensional attenuation structure beneath the northeastern Japan arc estimated from spectra of small earthquakes.Tectonophysics,2000,319(4):241～260
[14]Salah M K,Zhao D P.Three-dimensional attenuation structure beneath southwest Japan estimated fromspectra of microearthquakes.Physics of the Earth and Planetary Interiors,2003,136:215～231
[15]Yoshimoto K,Wegler U,Korn M.A volcanic front as a boundary of seismic-attenuation structures in northeastern Honshu,Japan.Bulletin of the Seismological Society of America,2006,96(2):637～646
[16]Umino N,Hasegawa A.Three-dimensionalQsstructure in the northeastern Japan arc.Zisin2(J.Seism.Soc.Jpn)(in Japanese),1984,37:217～228
[17]Hashida T.Three-dimensional seismic attenuation structure beneath the Japanese Islands and its tectonic and thermal implications.Tectonophysics,1989,159:163～180
[18]李光品,徐果明,高尔根等.中国东部地壳、上地幔横波品质因子的三维层析成像.地震学报,2000,22(1):73～81Li G P,Xu G M,Gao E G,et al.Qtomography under the crust and upper mantle in eastern China.Acta Seismologica Sinica(in Chinese),2000,22(1):73～81
[19]丛连理,胡家富,傅竹武等.中国大陆及邻近地区Lg尾波的Q值分布.中国科学(D辑),2002,32(8):617～624Cong L L,Hu J F,Fu Z W,et al.Distribution of Lg codaQ in the Chinese continent and its adjacent regions.Science in China(Series D)(in Chinese),2002,32(8):617～624
[20]洪学海,朱介寿,曹家敏等.中国大陆地壳上地幔S波品质因子三维层析成像.地球物理学报,2003,46(5):642～651Hong X H,Zhu J S,Cao J M,et al.Tomography of the3-D S-wave quality factor of the crust and upper mantle in China.Chinese J.Geophys.(in Chinese),2003,46(5):642～651
[21]黄玉龙,郑斯华,刘杰等.广东地区地震动衰减和场地响应的研究.地球物理学报,2003,46(1):54～61Huang Y L,Zheng S H,Liu J,et al.Attenuation of ground motion and site response in Guangdong region.Chinese J.Geophys.(in Chinese),2003,46(1):54～61
[22]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.地球物理学报,2004,47(6):1044～1052Liu J H,Liu F T,Yan X W,et al.A study of Lg coda attenuation beneath north China:seismic imaging of Lg coda Q0.Chinese J.Geophys.(in Chinese),2004,47(6):1044～1052
[23]Phillips W S,Hartse H E,Rutledge J T.Amplitude ratio tomography for regional phaseQ.Geophys.Res.Lett.,2005,32,10.1029/2005GL023870
[24]Xie J,Wu Z,Liu R,et al.Tomographic regionalization of crustal LgQin eastern Eurasia.Geophys.Res.Lett.,2006,33,L03315,doi:10.1029/2005GL024410
[25]Kamata H,Kodama K.Volcanic history and tectonics of the southwest Japan arc.The Island Arc,1999,8:393～403
[26]Obara K,Kasahara K,Hori S,Okada Y.A densely distributed high-sensitivity seismograph network in Japan:Hi-net by National Research Institute for Earth Science and Disaster Prevention.Review of Scientific Instruments,2005,76,021301-doi:10.1063/1.1854197
[27]Pei S P,Zhao J M,Rowe C A,et al.MLamplitude tomography in north China.Bulletin of the Seismological Society of America,2006,96(4):1560～1566
[28]马宏生,汪素云,裴顺平等.川滇及周边地区地壳横波衰减的成像研究.地球物理学报,2007,50(2):465～471Ma HS,Wang S Y,Pei S P,et al.Q0tomography of S wave attenuationin Sichuan-Yunnan and adjacent regions.Chinese J.Geophys.(in Chinese),2007,50(2):465～471
[29]汪素云,裴顺平,许忠淮等.利用ML振幅研究地壳横波Q值I:不同构造区的衰减特征.地球物理学报,2007,50(6):1740～1747Wang S Y,Pei S P,Xu Z H,et al.Crustal S-waveQ estimated fromMLamplitude I:attenuation in different tectonic regions of China.Chinese J.Geophys.(in Chinese),2007,50(6):1740～1747
[30]汪素云,裴顺平,Thomas M Hearn等.利用ML振幅研究地壳横波Q值II:Q横向变化特征.地球物理学报,2008,51(1):133～139Wang S Y,Pei S P,Hearn T M,et al.Crustal S-waveQ estimated fromMLamplitude II:Qlateral variationin China.Chinese J.Geophys.(in Chinese),2008,51(1):133～139
[31]Sanders C O.Local earthquake tomography:attenuation theory and results.In:Seismic Tomography:Theory and Practice,edited by H.Iyer and K.Hirahara.Chapman and Hall,New York,1993.676～694
[32]Takenaka H,Mamada Y,Futamure H.Near-source effect on radiation pattern of high-frequency S waves:strong SH-SV mixing observed from aftershocks of the1997northwestern Kagoshima,Japan,earthquakes.Phys.Earth Planet.Interiors,2003,137:31～43
[33]Lees J M,Crosson R S.Tomographic inversion for three-dimensional velocity structure at mount St.Helens using earthquake data.J.Geophys.Res.1989,94:5716～5728
[34]Paige C C,Saunders M A.LSQR,An algorithmfor sparse linear equations and sparse linear system.ACM Trans.Math.Soft ware,1982,8:43～71
[35]Yoshimoto K,Sato H,Ohtake M.Frequency-dependent attenuation of P-wave and S-wave in the Kanto area,Japan,based on the coda-normalization method.Geophysical Journal International,1993,114(1):165～174
[36]Satoh T,Kawase H,Sato T.Statistical spectral model of earthquakes in the eastern Tohoku district,Japan,based on the surface and borehole records observedin Sendai.Bulletin ofthe Seismological Society of America,1997,87(2):446～462
[37]Nakajima J,Matsuzawa T,Hasegawa A,et al.Three-dimensional structure ofVp,VsandVp/Vsbeneath northeastern Japan:Implications for arc magmatism and fluids.J.Geophys.Res.,2001,106(B10):21843～21858
[38]Zhao D,Hasegawa A,Kanamori H.Deep structure of Japan subduction zone as derived from local,regional,and teleseismic events.J.Geophys.Res.1994,99(B11):22313～22329
[39]Salah M,Zhao D.3-D seismic structure of Kii Peninsula in southwest Japan:evidence for slab dehydration in the forearc.Tectonophysics,2003,364:191～213
[40]Rietbrock A.P wave attenuation structureinthe fault area of the1995Kobe earthquake.J.Geophys.Res.,2001,106:4141～4154
[2]Molas G L,Yamazaki F.Attenuation of earthquake ground motionin Japan including deep-focus events.Bulletin of the Seismological Society of America,1995,85(5):1343～1358
[3]Fukushima Y,Berce-Thierry C,Volant P,et al.Attenuation relation for west eurasia determined with recent near-fault records from California,Japan and Turkey.Journal of Earthquake Engineering,2003,7(4):573～598
[4]Mamada Y,Takenaka H.Strong attenuation of shear waves in the focal region of the1997Northwestern Kagoshima earthquakes,Japan.Bulletinofthe Seismological Society of America,2004,94(2):464～478
[5]Kanno T,Narita A,Morikawa N,et al.A newattenuation relation for strong ground motionin Japan based on recorded data.Bulletin of the Seismological Society of America,2006,96(3):879～897
[6]Zhao J X,Zhang J,Asano A,et al.Attenuation relations of strong ground motion in Japan using site classification based on predominant period.Bulletinofthe Seismological Society of America,2006,96(3):898～913
[7]Nakamura R,Satake K,Toda S,et al.Three-dimensional attenuation(Qs)structure beneaththe Kanto district,Japan,as inferredfromstrong motion records.Geophysical Research Letters,2006,33,L21304,doi:10.1029/2006GL027352
[8]Sekiguchi S.Three-dimensionalQstructure beneath the Kanto-Tokai district,Japan.Tectonophysics,1991,195:83～104
[9]Katsumata K,Urabe T,Mizoue M.Evidence for a seismic attenuation anomaly beneath the Hida mountain-range,Central Honshu,Japan.Geophysical Journal International,1995,120(2):237～246
[10]Tsumura N,Hasegawa A,Horiuchi S.Simultaneous estimation of attenuation structure,source parameters and site response spectra-Application to the northeastern part of Honshu,Japan.Physics of the Earth and Planetary Interiors,1996,93:105～121
[11]Yamamoto K,Ida Y.Significant P wave attenuation for aspecific frequency range beneath Kirishima Volcano,Japan.Geophysical Research Letters,1997,24(10):1275～1278
[12]Takanami T,Sacks I S,Hasegawa A.Attenuation structure beneath the volcanic front in northeastern Japan from broad-band seismograms.Physics of the Earth and Planetary Interiors,2000,121:339～357
[13]Tsumura N,Matsumoto S,Horiuchi S,et al.Three-dimensional attenuation structure beneath the northeastern Japan arc estimated from spectra of small earthquakes.Tectonophysics,2000,319(4):241～260
[14]Salah M K,Zhao D P.Three-dimensional attenuation structure beneath southwest Japan estimated fromspectra of microearthquakes.Physics of the Earth and Planetary Interiors,2003,136:215～231
[15]Yoshimoto K,Wegler U,Korn M.A volcanic front as a boundary of seismic-attenuation structures in northeastern Honshu,Japan.Bulletin of the Seismological Society of America,2006,96(2):637～646
[16]Umino N,Hasegawa A.Three-dimensionalQsstructure in the northeastern Japan arc.Zisin2(J.Seism.Soc.Jpn)(in Japanese),1984,37:217～228
[17]Hashida T.Three-dimensional seismic attenuation structure beneath the Japanese Islands and its tectonic and thermal implications.Tectonophysics,1989,159:163～180
[18]李光品,徐果明,高尔根等.中国东部地壳、上地幔横波品质因子的三维层析成像.地震学报,2000,22(1):73～81Li G P,Xu G M,Gao E G,et al.Qtomography under the crust and upper mantle in eastern China.Acta Seismologica Sinica(in Chinese),2000,22(1):73～81
[19]丛连理,胡家富,傅竹武等.中国大陆及邻近地区Lg尾波的Q值分布.中国科学(D辑),2002,32(8):617～624Cong L L,Hu J F,Fu Z W,et al.Distribution of Lg codaQ in the Chinese continent and its adjacent regions.Science in China(Series D)(in Chinese),2002,32(8):617～624
[20]洪学海,朱介寿,曹家敏等.中国大陆地壳上地幔S波品质因子三维层析成像.地球物理学报,2003,46(5):642～651Hong X H,Zhu J S,Cao J M,et al.Tomography of the3-D S-wave quality factor of the crust and upper mantle in China.Chinese J.Geophys.(in Chinese),2003,46(5):642～651
[21]黄玉龙,郑斯华,刘杰等.广东地区地震动衰减和场地响应的研究.地球物理学报,2003,46(1):54～61Huang Y L,Zheng S H,Liu J,et al.Attenuation of ground motion and site response in Guangdong region.Chinese J.Geophys.(in Chinese),2003,46(1):54～61
[22]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.地球物理学报,2004,47(6):1044～1052Liu J H,Liu F T,Yan X W,et al.A study of Lg coda attenuation beneath north China:seismic imaging of Lg coda Q0.Chinese J.Geophys.(in Chinese),2004,47(6):1044～1052
[23]Phillips W S,Hartse H E,Rutledge J T.Amplitude ratio tomography for regional phaseQ.Geophys.Res.Lett.,2005,32,10.1029/2005GL023870
[24]Xie J,Wu Z,Liu R,et al.Tomographic regionalization of crustal LgQin eastern Eurasia.Geophys.Res.Lett.,2006,33,L03315,doi:10.1029/2005GL024410
[25]Kamata H,Kodama K.Volcanic history and tectonics of the southwest Japan arc.The Island Arc,1999,8:393～403
[26]Obara K,Kasahara K,Hori S,Okada Y.A densely distributed high-sensitivity seismograph network in Japan:Hi-net by National Research Institute for Earth Science and Disaster Prevention.Review of Scientific Instruments,2005,76,021301-doi:10.1063/1.1854197
[27]Pei S P,Zhao J M,Rowe C A,et al.MLamplitude tomography in north China.Bulletin of the Seismological Society of America,2006,96(4):1560～1566
[28]马宏生,汪素云,裴顺平等.川滇及周边地区地壳横波衰减的成像研究.地球物理学报,2007,50(2):465～471Ma HS,Wang S Y,Pei S P,et al.Q0tomography of S wave attenuationin Sichuan-Yunnan and adjacent regions.Chinese J.Geophys.(in Chinese),2007,50(2):465～471
[29]汪素云,裴顺平,许忠淮等.利用ML振幅研究地壳横波Q值I:不同构造区的衰减特征.地球物理学报,2007,50(6):1740～1747Wang S Y,Pei S P,Xu Z H,et al.Crustal S-waveQ estimated fromMLamplitude I:attenuation in different tectonic regions of China.Chinese J.Geophys.(in Chinese),2007,50(6):1740～1747
[30]汪素云,裴顺平,Thomas M Hearn等.利用ML振幅研究地壳横波Q值II:Q横向变化特征.地球物理学报,2008,51(1):133～139Wang S Y,Pei S P,Hearn T M,et al.Crustal S-waveQ estimated fromMLamplitude II:Qlateral variationin China.Chinese J.Geophys.(in Chinese),2008,51(1):133～139
[31]Sanders C O.Local earthquake tomography:attenuation theory and results.In:Seismic Tomography:Theory and Practice,edited by H.Iyer and K.Hirahara.Chapman and Hall,New York,1993.676～694
[32]Takenaka H,Mamada Y,Futamure H.Near-source effect on radiation pattern of high-frequency S waves:strong SH-SV mixing observed from aftershocks of the1997northwestern Kagoshima,Japan,earthquakes.Phys.Earth Planet.Interiors,2003,137:31～43
[33]Lees J M,Crosson R S.Tomographic inversion for three-dimensional velocity structure at mount St.Helens using earthquake data.J.Geophys.Res.1989,94:5716～5728
[34]Paige C C,Saunders M A.LSQR,An algorithmfor sparse linear equations and sparse linear system.ACM Trans.Math.Soft ware,1982,8:43～71
[35]Yoshimoto K,Sato H,Ohtake M.Frequency-dependent attenuation of P-wave and S-wave in the Kanto area,Japan,based on the coda-normalization method.Geophysical Journal International,1993,114(1):165～174
[36]Satoh T,Kawase H,Sato T.Statistical spectral model of earthquakes in the eastern Tohoku district,Japan,based on the surface and borehole records observedin Sendai.Bulletin ofthe Seismological Society of America,1997,87(2):446～462
[37]Nakajima J,Matsuzawa T,Hasegawa A,et al.Three-dimensional structure ofVp,VsandVp/Vsbeneath northeastern Japan:Implications for arc magmatism and fluids.J.Geophys.Res.,2001,106(B10):21843～21858
[38]Zhao D,Hasegawa A,Kanamori H.Deep structure of Japan subduction zone as derived from local,regional,and teleseismic events.J.Geophys.Res.1994,99(B11):22313～22329
[39]Salah M,Zhao D.3-D seismic structure of Kii Peninsula in southwest Japan:evidence for slab dehydration in the forearc.Tectonophysics,2003,364:191～213
[40]Rietbrock A.P wave attenuation structureinthe fault area of the1995Kobe earthquake.J.Geophys.Res.,2001,106:4141～4154
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