西南日本地区地壳P、S波速度结构与地震活动的关系
摘要
选用密集的高精度地震台网Hi-net 2002~2004年记录的836个地震事件的23,895条P波和21,969条S波的到时资料,计算得到了日本西南地区水平分辨率约33 km,垂直分辨率4~15 km的三维地壳P波和S波速度结构,并进一步获得泊松比分布.研究表明,在大山火山下存在显著的低速异常,表明该火山可能是一个潜在的活火山.速度异常图像清楚地显示了菲律宾板块俯冲至西南日本地区下,其上方存在的低速高泊松异常表明可能有流体的存在,分析得出可能来自板块俯冲过程中的脱水作用.并进一步探讨了流体在地震孕育及触发的过程中可能起的重要作用.
We used 23,895 P and 21,969 S wave high-quality arrival times from 836 local earthquakes during 2002 to 2004 recorded by the dense High-sensitivity Seismic Network(Hi-net) on the Japan islands.Detailed three-dimensional seismic velocity(Vp and Vs) structures of the crust under Southwest Japan are determined with a horizontal resolution of about 33 km and a depth resolution of 4~15km.We also estimated the Poisson's ratio(σ) structure by using the inverted Vp and Vs data.Our results revealed a significant low-velocity anomaly beneath the Daisen volcano,which suggests that Daisen is potentially an active volcano.The subducting Philippine Sea plate is clearly imaged beneath Southwest Japan.Low-velocity and high-Poisson's ratio anomalies are visible above the Philippine Sea slab,which may indicate the existence of fluids released by the slab dehydration.In addition,we discuss the important role of fluids played in the generating and triggering processes of large crustal earthquakes.
We used 23,895 P and 21,969 S wave high-quality arrival times from 836 local earthquakes during 2002 to 2004 recorded by the dense High-sensitivity Seismic Network(Hi-net) on the Japan islands.Detailed three-dimensional seismic velocity(Vp and Vs) structures of the crust under Southwest Japan are determined with a horizontal resolution of about 33 km and a depth resolution of 4~15km.We also estimated the Poisson's ratio(σ) structure by using the inverted Vp and Vs data.Our results revealed a significant low-velocity anomaly beneath the Daisen volcano,which suggests that Daisen is potentially an active volcano.The subducting Philippine Sea plate is clearly imaged beneath Southwest Japan.Low-velocity and high-Poisson's ratio anomalies are visible above the Philippine Sea slab,which may indicate the existence of fluids released by the slab dehydration.In addition,we discuss the important role of fluids played in the generating and triggering processes of large crustal earthquakes.
引文
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[28]Paige C,Saunders M.LSQR:Sparse linear equations andleast squares problems[J].ACM Trans.Math.Softw.,1982,8:195~209.
[29]Zhao D,Hasegawa A,Kanamori H.Deep structure of Japansubduction zones as derived from local,regional and teleseis-mic events[J].J.Geophys.Res.,1994,99:22313~22329.
[30]Christensen N.Poisson’s ratio and crustal seismology[J].J.Geophys.Res.,1996,101:3139~3156.
[31]Zhao D,Mishra O P,Sanda R.Influence of fluids and mag-ma on earthquakes:seismological evidence[J].Phys.EarthPlanet.Inter.,2002,132:249~267.
[32]Zhao D,Horiuchi S,Hasegawa A.Seismic velocity structureof the crust beneath the Japan Islands[J].Tectonophysics,1992,212:289~301.
[33]Zhao D,Ochi F,Hasegawa A,et a1.Evidence for the loca-tion and cause of large crustal earthquakes in Japan[J].J.Geophys.Res.,2000,105:13579~13594.
[34]Salah M,Zhao D.3~D seismic structure of Kii Peninsula insouthwest Japan:evidence for slab dehydration in the forearc[J].Tectonophysics,2003,364:191~213.
[35]Mishra O P,Zhao D.Crack density,saturation rate and po-rosity at the 2001 Bhuj,India,earthquake hypocenter:a flu-id driven earthquake?[J].Earth Planet.Sci.Lett.,2003,212:393~405.
[36]Nakanishi I,Kinoshita Y,Miura K.Subduction of youngplates:A case of the Philippine Sea plate beneath the Ch-ugoku region,Japan[J].Earth Planets Space,2002,54:3~8.
[37]孙若昧,刘福田.京津唐地区地壳结构与强震的发生-I.P波速度结构[J].地球物理学报,1995,38(5):599~607.Sun R,LiuF T.Crust structure and strong earthquake inBeijing.Tianjin,Tangshan area:1.P wave velocity structure[J].Chinese J.Geophys.,1995,38(5):599~607.
[38]Huang J L,Zhao D P.Crustal heterogeneity and seismotec-tonics of the region around Beijing,China[J].Tectonophys-ics.2004,385:159~180.
[39]齐诚,赵大鹏,陈颙,等.首都圈地区地壳P波和S波三维速度结构及其与大地震的关系[J].地球物理学报,2006,49(3):805~815.Qi C,Zhao D,Chen Y,et al.3-D P and S wave velocitystructures and their relationship to strong earthquakes in theChinese capital region[J].Chinese J.Geophys.,2006,49(3):805~815.
[40]Sun A H,Zhao D P,IKEDA M,et al.Seismic imaging ofsouthwest Japan using P and PmP data:Implications for arcmagmatism and seismotectonics[J].Gondwana Research,2008,14(3):535~542.
[41]Wessel P,Smith W.New version of the Generic MappingTools released[J].EOS,1995,76:329.
[2]Aki K,Christoffersson A,Husebye E S.Determination of thethree dimensional seismic structure of the lithosphere[J].J.Geophys.Res.,1977,82:277~296.
[3]Dziewonski A M,Hager B,O’Connell R.Large~scale het-erogeneities in the lower mantle[J].J.Geophys.Res.,1977,82:23~55.
[4]Dziewonski A M.Mapping the lower mantle:determination oflateral heterogeneity in P velocity up to degree and order 6[J].J.Geophys.Res.,1984,89:5929~5952.
[5]Zhao D,Hasegawa A,Horiuchi S.Tomographic imaging of Pand S wave velocity structure beneath northeastern Japan[J].J.Geophys.Res.,1992,97:19909~19928.
[6]Kodaira S,Kurashimo E,Park J O,et al.Structural factorscontrolling the rupture process of a megathrust earthquake atthe Nankai trough seismogenic zone[J].Geophys.J.Int.,2002,149:815~835.
[7]Seno T,Stein S,Gripp A.A model for the motion of the Phil-ippine Sea plate consistent with NUVEL~1 and geological da-ta[J].J.Geophys.Res.,1993,98:17941~17948.
[8]Iwamori H.Zonal structure of Cenozoic basalts related tomantle upwelling in southwest Japan[J].J.Geophys.Res.,1991,96:6157~6170.
[9]Zhao D,Kanamori H,Negishi H.Tomography of the sourcearea of the 1995 Kobe earthquake:evidence for fluids at thehypocenter?[J].Science,1996,274:1891~1984.
[10]Zhao D,Negishi H.The 1995 Kobe earthquake:seismic im-age of the source zone and its implications for the rupture nu-cleation[J].J.Geophys.Res.,1998,103:9967~9986.
[11]Zhao D,Mizuno T.Crack density and saturation rate in the1995 Kobe earthquake region[J].Geophys.Res.Lett.,1999,26:3213~3216.
[12]Zhao D,Tani H,Mishra O P.Crustal heterogeneity in the2000 western Tottori earthquake region:effect of fluids fromslab dehydration[J].Phys.Earth Planet.Inter.,2004,145:161~177.
[13]Salah M,Zhao D.Mapping the crustal thickness in south-west Japan using Moho-reflected waves[J].Phys.EarthPlanet.Inter.,2004,141:79~94.
[14]Salah M,Zhao D,Lei J,et al.Crustal heterogeneity beneathsouthwest Japan estimated from direct and Moho-reflectedwaves[J].Tectonophysics,2005,395:1~17.
[15]Ikeda M,Zhao D,Ohno Y.Crustal structure,fault segmen-tation,and activity of the Median Tectonic Line in Shikoku,Japan[J].Tectonophysics,2006,412:49~60.
[16]Obara K.Nonvolcanic deep tremor,associated with subduc-tion in southwest Japan[J].Science,2002,296:1679~1681.
[17]Wang Z,Zhao D,Mishra O P,et a1.Structural heterogenei-ty and its implications for the low frequency tremors in South-west Japan[J].Earth Planet Sci.Lett.,2006,251:66~78.
[18]Zhao D,Horiuchi S,Hasegawa A.3~D seismic velocitystructure of the crust and uppermost mantle in the northeast-ern Japan arc[J].Tectonophysics,1990,181:135~149.
[19]Zhao D,Matsuzawa T,Hasegawa A.Morphology of thesubducting slab boundary in the northeastern Japan arc[J].Phys.Earth Planet.Inter.,1997,102:89~104.
[20]杨卓欣,张先康,赵金仁,等.长白山天池火山区三维地壳结构层析成像[J].地球物理学报,2005,48(1):106~114.Yang Z X,Zhang X K,Zhao J R,et al.Tomographic ima-ging of 3-D crustal structure beneath Changbaishan-Tianchivolcano region[J].Chinese J.Geophys.(in Chinese),2005,48(1):106~114.
[21]吴建平,明跃红,王椿镛.川滇地区速度结构的区域地震波形反演研究[J].地球物理学报,2006,49(5):1369~1376.Wu J P,Ming Y H,Wang C Y.Regional waveform inversionfor crustal and upper mantle velocity structure below Chuan-dian region[J].Chinese J.Geophys.(in Chinese),2006,49(5):1369~1376.
[22]胥颐,刘建华,刘福田,等.天山-帕米尔结合带的地壳速度结构及地震活动研究[J].地球物理学报,2006,49(2):469~476.Xu Y,Liu J H,Liu F T,et al.Crustal velocity structure andseismic activity in the Tianshan-Pamir conjunctive zone[J].Chinese J.Geophys.(in Chinese),2006,49(2):469~476.
[23]周民都,张元生,石雅镠,等.青藏高原东北缘地壳三维速度结构[J].地球物理学进展,2006,21(1):127~134.Zhou M D,Zhang Y S,Shi Y L,et al.Three-dimensionalcrustal velocity structure in the northeastern margin of theQinghai-Tibetan plateau[J].Progress in Geophysics(in Chi-nese),2006,21(1):127~134.
[24]Huang J,Zhao D.High-resolution mantle tomography ofChina and surrounding regions[J].J.Geophys.Res.,2006,111:B09305,2005JB004066.
[25]胥颐,刘建华,郝天珧,等.中国东部海域及邻区岩石层地幔的P波速度结构与构造分析[J].地球物理学报,2006,49(4):1053~1061.Xu Y,Liu J H,Hao T Y,et al.P wave velocity structureand tectonics analysis of lithospheric mantle in eastern Chinaseas and adjacent regions[J].Chinese J.Geophys.(in Chi-nese),2006,49(4):1053~1061.
[26]李永华,吴庆举,安张辉,等.青藏高原东北缘地壳S波速度结构与泊松比及其意义[J].地球物理学报,2006,49(5):1359~1368.Li Y H,Wu Q J,An Z H,et al.The Poisson ratio and crus-tal structure across the NE Tibetan Plateau determined fromreceiver functions[J].Chinese J.Geophys.(in Chinese),2006,49(5):1359~1368
[27]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[J].地球物理学报,2007,50(2):465~471.Ma H S,Wang S Y,Pei S P,et al.Q0 tomography of Swave attenuation in Sichuan-Yunnan and adjacent regions[J].Chinese J.Geophys.(in Chinese),2007,50(2):465~471
[28]Paige C,Saunders M.LSQR:Sparse linear equations andleast squares problems[J].ACM Trans.Math.Softw.,1982,8:195~209.
[29]Zhao D,Hasegawa A,Kanamori H.Deep structure of Japansubduction zones as derived from local,regional and teleseis-mic events[J].J.Geophys.Res.,1994,99:22313~22329.
[30]Christensen N.Poisson’s ratio and crustal seismology[J].J.Geophys.Res.,1996,101:3139~3156.
[31]Zhao D,Mishra O P,Sanda R.Influence of fluids and mag-ma on earthquakes:seismological evidence[J].Phys.EarthPlanet.Inter.,2002,132:249~267.
[32]Zhao D,Horiuchi S,Hasegawa A.Seismic velocity structureof the crust beneath the Japan Islands[J].Tectonophysics,1992,212:289~301.
[33]Zhao D,Ochi F,Hasegawa A,et a1.Evidence for the loca-tion and cause of large crustal earthquakes in Japan[J].J.Geophys.Res.,2000,105:13579~13594.
[34]Salah M,Zhao D.3~D seismic structure of Kii Peninsula insouthwest Japan:evidence for slab dehydration in the forearc[J].Tectonophysics,2003,364:191~213.
[35]Mishra O P,Zhao D.Crack density,saturation rate and po-rosity at the 2001 Bhuj,India,earthquake hypocenter:a flu-id driven earthquake?[J].Earth Planet.Sci.Lett.,2003,212:393~405.
[36]Nakanishi I,Kinoshita Y,Miura K.Subduction of youngplates:A case of the Philippine Sea plate beneath the Ch-ugoku region,Japan[J].Earth Planets Space,2002,54:3~8.
[37]孙若昧,刘福田.京津唐地区地壳结构与强震的发生-I.P波速度结构[J].地球物理学报,1995,38(5):599~607.Sun R,LiuF T.Crust structure and strong earthquake inBeijing.Tianjin,Tangshan area:1.P wave velocity structure[J].Chinese J.Geophys.,1995,38(5):599~607.
[38]Huang J L,Zhao D P.Crustal heterogeneity and seismotec-tonics of the region around Beijing,China[J].Tectonophys-ics.2004,385:159~180.
[39]齐诚,赵大鹏,陈颙,等.首都圈地区地壳P波和S波三维速度结构及其与大地震的关系[J].地球物理学报,2006,49(3):805~815.Qi C,Zhao D,Chen Y,et al.3-D P and S wave velocitystructures and their relationship to strong earthquakes in theChinese capital region[J].Chinese J.Geophys.,2006,49(3):805~815.
[40]Sun A H,Zhao D P,IKEDA M,et al.Seismic imaging ofsouthwest Japan using P and PmP data:Implications for arcmagmatism and seismotectonics[J].Gondwana Research,2008,14(3):535~542.
[41]Wessel P,Smith W.New version of the Generic MappingTools released[J].EOS,1995,76:329.
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