2003年大姚6.2和6.1级地震前三维波速结构的演化
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摘要
尝试在年度尺度上对云南地区地壳速度结构进行成像,以确定2003年大姚地震前三维地壳速度结构的演化,并对其发震成因的介质物性变化进行探讨.检测板分辨试验显示,在年度尺度上,大姚附近区域15km深度上节点解的分辨率在0.6左右;误差分析显示,在震源附近的误差(约0.02km/s)远小于速度变化的幅度(约0.15km/s).研究结果表明,大姚地震前震源区附近形成一条北北西向的高、低波速交界带,其走向与两次大姚地震震源机制解的走向以及通过余震精定位确定的断层走向基本吻合,且震源位于交界带的高波速一侧.此外,大姚地震震后在震源下方形成一低速体.本文得到的大姚地震前的波速结构演化可为探讨其孕震、发震条件提供约束.
In this paper the crustal velocity structure are imaged at the annual scale for determining the evolution of 3D velocity structure before the Dayao earthquakes in 2003, and the physical variety of medium are discussed about the cause of earthquake occurrence. The checkerboard resolution tests show that the spatial resolution at 15 km depth is approximate 0.6 around Dayao. The error analyses show that the error (approximate 0.02 km/s) at the focus area is far smaller than the magnitude (approximate 0.15 km/s) of velocity variation. The results of studies show that a NNW-striking juncture zone of high- and low-velocity is produced before Dayao earthquake, whose strike is basically consistent with that of aftershock distribution of Dayao earthquakes and the focal mechanism, and the hypocenters lie on the high-velocity side of juncture zone. Furthermore, there is a low-velocity body under the hypocenters after Dayao earthquakes. The evolution of velocity structure provides restriction for discussing the circumstances of earthquake gestating and occurring.
In this paper the crustal velocity structure are imaged at the annual scale for determining the evolution of 3D velocity structure before the Dayao earthquakes in 2003, and the physical variety of medium are discussed about the cause of earthquake occurrence. The checkerboard resolution tests show that the spatial resolution at 15 km depth is approximate 0.6 around Dayao. The error analyses show that the error (approximate 0.02 km/s) at the focus area is far smaller than the magnitude (approximate 0.15 km/s) of velocity variation. The results of studies show that a NNW-striking juncture zone of high- and low-velocity is produced before Dayao earthquake, whose strike is basically consistent with that of aftershock distribution of Dayao earthquakes and the focal mechanism, and the hypocenters lie on the high-velocity side of juncture zone. Furthermore, there is a low-velocity body under the hypocenters after Dayao earthquakes. The evolution of velocity structure provides restriction for discussing the circumstances of earthquake gestating and occurring.
引文
陈培善,刘福田,李强,等.1990.云南地区速度结构的横向不均匀性[J].中国科学(B辑),(4):431-438.
冯德益.1981.地震波速异常[M].北京:地震出版社:14-15.
何正勤,叶太兰,苏伟.2004.云南地区地壳中上部横波速度结构研究[J].地球物理学报,47(5):838-844.
华卫,刘杰,郑斯华,等.2006.2003年云南大姚6.2、6.1级地震序列特征分析及触发研究[J].中国地震,22(1):10-23.
阚荣举,张四昌,晏凤桐,等.1977.我国西南地区现代构造应力场与现代构造活动特征的探讨[J].地球物理学报,20(2):96-109.
刘福田,李强,吴华,等.1989.用于速度图像重建的层析成像法[J].地球物理学报,32(1):46-61.
刘建华,刘福田,吴华,等.1989.中国南北带地壳和上地幔的三维速度结构[J].地球物理学报,32(2):143-151.
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刘志,张先康,王夫运,等.2005.用地震走时反演计算长白山天池火山区二维地壳泊松比[J].地震学报,27(3):324-331.
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孙若昧,刘福田.1995.京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,38(5):599-607.
王椿镛,王溪莉,颜其中.1994.昆明地震台网下方的三维速度结构[J].地震学报,16(2):167-175.
王椿镛,Mooney WD,王溪莉,等.2002.川滇地区地壳上地幔三维速度结构研究[J].地震学报,24(1):1-16.
吴建平,明跃红,王椿镛.2001.云南数字地震台站下方的S波速度结构研究[J].地球物理学报,44(2):228-237.
Aki K,Lee W H K.1976.Determination of three-di mensional velocity anomalies under a seismic array using P arrivalti mes fromlocal earthquakes(1):A homogeneous initial model[J].J Geophys Res,81:4381-4399.
Aki K,Richards P G.1980.Quantitative Seismology,Vol.2[M].San Francisco:W H Freeman and Company:675-689.
Franklin J N.1970.Well-posed stochastic extensions of ill-posedlinear problems[J].J Math Anal Applic,31:682-716.
Huang J,Zhao D,Zheng S.2002.Lithosperic structure andits relationship to seismic and volcanic activityin southwestChina[J].J Geophys Res,107(B10):doi:10.1029/2000JB000137.
Humphreys E,Clayton R W.1988.Adaptation of back projectiontomographyto seismic travel ti me problems[J].J Geo-phys Res,93:1073-1085.
Inoue H,Fukao Y,Tanabe K,et al.1990.Whole mantle P-wave travel ti me tomography[J].Phys Earth Planet Interi,59:294-328.
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Kodaira S,Lidaka T,Kato A,et al.2004.High pore fluid pressure may cause silent slipin the Nankai trough[J].Sci-ence,304:1295-1298.
Lutter WJ,Nowack R L.1990.Inversionfor crustal structure using reflections fromthe PASSCAL Ouachita experi ment[J].J Geophys Res,95:4621-4631.
Tatham R H.1982.vP/vSand lithology[J].Geophysics,47:336-344.
Thurber C H.1983.Earthquakelocations andthree-di mensional crustal structureinthe Coyotelate area,Central Califor-nia[J].J Geophys Res,88:8226-8236.
Thurber C H,Atre S R.1993.Three-di mensionalvP/vSvariations along the Loma Prieta rupture zone[J].Bull SeismSoc Amer,83:717-736.
Walck MC.1988.Three-Di mensionalvP/vSvariations for the Coso region,California[J].J Geophys Res,93:2047-2052.
Wiggins R A.1972.The general linear inverse problem:I mplication of surface waves andfree oscillations for earth struc-ture[J].Rev Geophys Space Phys,10:251-285.
Zhao D,Hasegawa A,Horiuchi S.1992.Tomographic i maging of P and S wave velocity structure beneath northeasternJapen[J].J Geophys Res,97:19909-19928.
Zhao D,Kanamori H,Negishi H.1996.Tomography of the source zone of the1995Kobe earthquake:Evidence for flu-ids at the hypocenter?[J].Science,274:1891-1894.
Zhao D,Negishi H.1998.The1995Kobe earthquake:Seismic i mage of the source zone andits i mplications for the rup-ture nucleation[J].J Geophys Res,103:9967-9987.
Zhao D,Mishra O,Sanda R.2002.Influence of fluids and magma on earthquakes:Seismological evidence[J].PhysEarth Planet Interi,102:249-267.
冯德益.1981.地震波速异常[M].北京:地震出版社:14-15.
何正勤,叶太兰,苏伟.2004.云南地区地壳中上部横波速度结构研究[J].地球物理学报,47(5):838-844.
华卫,刘杰,郑斯华,等.2006.2003年云南大姚6.2、6.1级地震序列特征分析及触发研究[J].中国地震,22(1):10-23.
阚荣举,张四昌,晏凤桐,等.1977.我国西南地区现代构造应力场与现代构造活动特征的探讨[J].地球物理学报,20(2):96-109.
刘福田,李强,吴华,等.1989.用于速度图像重建的层析成像法[J].地球物理学报,32(1):46-61.
刘建华,刘福田,吴华,等.1989.中国南北带地壳和上地幔的三维速度结构[J].地球物理学报,32(2):143-151.
刘志,张先康,周雪松,等.2003.帕米尔东北侧地壳物性结构及其发震环境探讨[J].地震学报,25(3):242-249.
刘志,张先康,王夫运,等.2005.用地震走时反演计算长白山天池火山区二维地壳泊松比[J].地震学报,27(3):324-331.
马杏垣,宿俭,吴大宁.1987.中国的活动块体与构造变形[M].北京:地震出版社:1-8.
孙若昧,刘福田.1995.京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,38(5):599-607.
王椿镛,王溪莉,颜其中.1994.昆明地震台网下方的三维速度结构[J].地震学报,16(2):167-175.
王椿镛,Mooney WD,王溪莉,等.2002.川滇地区地壳上地幔三维速度结构研究[J].地震学报,24(1):1-16.
吴建平,明跃红,王椿镛.2001.云南数字地震台站下方的S波速度结构研究[J].地球物理学报,44(2):228-237.
Aki K,Lee W H K.1976.Determination of three-di mensional velocity anomalies under a seismic array using P arrivalti mes fromlocal earthquakes(1):A homogeneous initial model[J].J Geophys Res,81:4381-4399.
Aki K,Richards P G.1980.Quantitative Seismology,Vol.2[M].San Francisco:W H Freeman and Company:675-689.
Franklin J N.1970.Well-posed stochastic extensions of ill-posedlinear problems[J].J Math Anal Applic,31:682-716.
Huang J,Zhao D,Zheng S.2002.Lithosperic structure andits relationship to seismic and volcanic activityin southwestChina[J].J Geophys Res,107(B10):doi:10.1029/2000JB000137.
Humphreys E,Clayton R W.1988.Adaptation of back projectiontomographyto seismic travel ti me problems[J].J Geo-phys Res,93:1073-1085.
Inoue H,Fukao Y,Tanabe K,et al.1990.Whole mantle P-wave travel ti me tomography[J].Phys Earth Planet Interi,59:294-328.
Jackson D D.1972.Interpretation of inaccurate insufficient andinconsisitent data[J].Geophys J R astr Soc,28:97-110.
Kodaira S,Lidaka T,Kato A,et al.2004.High pore fluid pressure may cause silent slipin the Nankai trough[J].Sci-ence,304:1295-1298.
Lutter WJ,Nowack R L.1990.Inversionfor crustal structure using reflections fromthe PASSCAL Ouachita experi ment[J].J Geophys Res,95:4621-4631.
Tatham R H.1982.vP/vSand lithology[J].Geophysics,47:336-344.
Thurber C H.1983.Earthquakelocations andthree-di mensional crustal structureinthe Coyotelate area,Central Califor-nia[J].J Geophys Res,88:8226-8236.
Thurber C H,Atre S R.1993.Three-di mensionalvP/vSvariations along the Loma Prieta rupture zone[J].Bull SeismSoc Amer,83:717-736.
Walck MC.1988.Three-Di mensionalvP/vSvariations for the Coso region,California[J].J Geophys Res,93:2047-2052.
Wiggins R A.1972.The general linear inverse problem:I mplication of surface waves andfree oscillations for earth struc-ture[J].Rev Geophys Space Phys,10:251-285.
Zhao D,Hasegawa A,Horiuchi S.1992.Tomographic i maging of P and S wave velocity structure beneath northeasternJapen[J].J Geophys Res,97:19909-19928.
Zhao D,Kanamori H,Negishi H.1996.Tomography of the source zone of the1995Kobe earthquake:Evidence for flu-ids at the hypocenter?[J].Science,274:1891-1894.
Zhao D,Negishi H.1998.The1995Kobe earthquake:Seismic i mage of the source zone andits i mplications for the rup-ture nucleation[J].J Geophys Res,103:9967-9987.
Zhao D,Mishra O,Sanda R.2002.Influence of fluids and magma on earthquakes:Seismological evidence[J].PhysEarth Planet Interi,102:249-267.
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