1992年美国加州兰德斯地震——地壳结构不均匀性对地震发生的影响
|
摘要
为了理解地震的发生和地壳结构不均匀性的关系,利用南加州地震台网的固定台和临时台所记录的2863个兰德斯余震和区域地震,共计107401个P波和19624个S波高质量的到时数据,采用地震层析成像方法得到了兰德斯地震区P波和S波的精细的三维速度结构和泊松比分布.结果显示,地震的发生和分布与地壳结构的横向不均匀性有密切的关系.总体上看,兰德斯地震区余震成丛分布,并被低速块体截断,其中4级以上地震大多分布于P波高、低速异常过渡区域或偏向高速块体一侧,这可能是因为高速区多属地壳脆性介质,易于造成应力集中,导致地震;反之,低速度区则可能代表破碎程度较高、富含流体或温度较高区域,因而更倾向于产生无震变形.基于兰德斯地震区强震震源位置、地震区P波、S波速度异常与泊松比分布推断,兰德斯地震区可能有流体存在.地壳流体易使地壳岩石弱化,从而引发大地震.
In order to understand the relationship between earthquake occurrence and crustal heterogeneities,we used 107401 P-and 19624 S-wave high-quality arrival times from the 1992 Landers aftershocks and other local earthquakes which were recorded by both permanent and temporary stations in Southern California to determine detailed three-dimensional P-and S-wave velocity and Poisson's ratio structures beneath the Landers earthquake area.Our results show a close correlation between the seismic rupture zones and crustal heterogeneities.The distribution of the Landers aftershocks is cluster-like and separated by or terminated in the area where low-velocity anomalies exist.Most of the large earthquakes with magnitudes bigger than 4 occur in or around areas with high P-wave velocity.The possibility is that high-velocity areas are probably brittle and strong parts which can sustain seismogenic stress,and so can generate earthquakes.In contrast,low-velocity areas may have either higher degree of fracture,high fluid content,or higher temperatures where deformation is more likely to be aseismic.In addition,we infer that fluids exist in the Landers earthquake area from the distribution of P-and S-wave velocity and Poisson's ratio.The existence of fluids may weaken the surrounding crustal rocks,then trigger strong earthquakes.
In order to understand the relationship between earthquake occurrence and crustal heterogeneities,we used 107401 P-and 19624 S-wave high-quality arrival times from the 1992 Landers aftershocks and other local earthquakes which were recorded by both permanent and temporary stations in Southern California to determine detailed three-dimensional P-and S-wave velocity and Poisson's ratio structures beneath the Landers earthquake area.Our results show a close correlation between the seismic rupture zones and crustal heterogeneities.The distribution of the Landers aftershocks is cluster-like and separated by or terminated in the area where low-velocity anomalies exist.Most of the large earthquakes with magnitudes bigger than 4 occur in or around areas with high P-wave velocity.The possibility is that high-velocity areas are probably brittle and strong parts which can sustain seismogenic stress,and so can generate earthquakes.In contrast,low-velocity areas may have either higher degree of fracture,high fluid content,or higher temperatures where deformation is more likely to be aseismic.In addition,we infer that fluids exist in the Landers earthquake area from the distribution of P-and S-wave velocity and Poisson's ratio.The existence of fluids may weaken the surrounding crustal rocks,then trigger strong earthquakes.
引文
[1]Zhao D,Kanamori H,Humphreys E.Simultaneous inversion of localand teleseismic data for the crust and mantle structure of southernCalifornia.Phys.Earth Planet.Inter.,1996,93:191~214
[2]滕吉文.地球内部物质、能量交换与资源和灾害.地学前缘,2001,8(3):1~8Teng J W.The exchange of substance and energy,different spherecoupling and deep dynamical process within the earth.Earth ScienceFrontiers,2001,8(3):1~8
[3]Sieh K,Jones E,Hauksson E,et al.Near-field investigations of theLanders earthquake sequence April to July 1992.Science,1993,260:171~176
[4]Zhao D,Kanamori H.The 1992 Landers earthquake sequence:earthquake occurrence and structural heterogeneities.Geophys.Res.Lett.,1992,19:1~4
[5]刘福田,李强,吴华等.用于速度图像重建的层析成像方法.地球物理学报,1989,32(1):46~61Liu F T,Li Q,Wu H,et al.Tomographical method used to imagereconstruction.Chinese J.Geophys.(Acta Geophysica Sinica)(inChinese),1989,32(1):46~61
[6]赵文津,薛光琦,吴珍汉等.西藏高原上地幔的精细结构与构造-地震层析成像给出的启示.地球物理学报,2004,47(3):449~455Zhao W J,Xue G Q,Wu S H,et al.Fine velocity structure of theupper mantle beneath thee Xizang Plateau from tomography and itsgeological interpretations.Chinese J.Geophys.(in Chinese),2004,47(3):449~455
[7]裴顺平,许忠淮,汪素云等.新疆及临区Pn速度层析成像.地球物理学报,2002,45(2):218~225Pei S P,Xu Z H,Wang S Y,et al.Pn velocity tomography ofXinjiang,China and adjacent region.Chinese J.Geophys.(inChinese),2002,45(2):218~225
[8]李志伟,胥颐,郝天珧等.环渤海地区的地震层析成像与地壳上地幔结构.地球物理学报,2006,49(3):797~804Li Z W,Xu Y,Hao T Y,et al.Seismic tomography and velocitystructure in the crust and upper mantle around Bohai Sea area.Chinese J.Geophys.(in Chinese),2006,49(3):797~804
[9]王夫运,张先康,陈棋福等.北京地区上地壳三维细节构层析成像.地球物理学报,2005,48(2):359~366Wang F Y,Zhang X K,Chen Q F,et al.Fine tomographic inversionof the upper crust 3D structure around Beijing.Chinese J.Geophys.(in Chinese),2005,48(2):359~366
[10]Zhao D,Hasegawa A,Horiuchi S.Tomographic imaging of P and Swave velocity structure beneath Northeastern Japan.J.Geophys.Res.,1992,97:19909~19928
[11]Zhao D,Hasegawa A,Kanamori H.Deep structure of Japansubduction zone as derived from local,regional and teleseismicevents.J.Geophys.Res.,1994,99:22313~22329
[12]Um J,Thurber C.A fast algorithm for two-point seismic ray tracing.Bull.Seism.Soc.Am.,1987,77:972~986
[13]Paige C,Saunders M.LSQR:An algorithm for sparse linear equationsand sparse least squares.Assoc.Comput.Mach Trans.Math.Software,1982,8:43~71
[14]Christensen N.Poisson’s ratio and crustal seismology.J.Geophys.Res.,1996,101:3139~3156
[15]Zhao D,Kanamori H,Negishi H.Tomography of the source area ofthe 1995 Kobe earthquake:evidence for fluids at the hypocenter?Science,1996,274:1891~1894
[16]Zhao D,Ochi F,Hasegawa A,Yamamoto A.Evidence for the locationand cause of large crustal earthquakes in Japan.J.Geophys.Res.,2000,105:13579~13594
[17]Zhao D,Mishra O,Sanda R.Influence of fluids and magma onearthquakes:seismological evidence.Phys.Earth Planet.Inter.,2002,132:249~267
[18]Humphreys E,Clayton R.Adaptation of back projection tomographyto seismic travel time problems.J.Geophys.Res.,1988,93:1073~1085
[19]黄金莉,赵大鹏,郑斯华.川滇活动构造区地震层析成像.地球物理学报,2001,44:127~135Huang J L,Zhao D P,Zheng S H.Seismic tomography of theSichuan-Yunnan activity tectonic region.Chinese J.Geophys.(inChinese),2001,44:127~135
[20]Eberhart-Phillips D.Three-dimensional velocity structure in NorthernCalifornia coast ranges from inversion of local earthquake arrivaltimes.Bull.Seismol.Soc.Am.,1986,76(4):1025~1052
[21]Kanamori H,Hadley D.Crustal structure and temporal velocitychange in Southern California.Pure and Appl.Geophys.,1975,113:257~280
[22]Lees J,Malin P.Tomographic images of P-wave velocity variations atParkfield,California.J.Geophys.Res.,1990,95:21793~21804
[23]Michade A,Eberhart-Plillips D.Relations among fault behavior,subsurface geology,and three-dimensional velocity models.Science,1991,253:651~654
[24]滕吉文,张秉铭,胡家富等.地震“孕育”的深部介质和构造环境研究.见:陈运泰主编.中国地震学研究进展-庆贺谢毓寿教授八十寿辰.北京:地震出版社,1997,258~265Teng J W,Zhang B M,Hu J F,et al.The research of deep mediumand structural environment of earthquake“pregnancy”.In:Chen Y Ted.Advances in Seismology in China:In Honour of Professor XieYushou’s 80th Birthday.Beijing:Seismological Press,1997.258~265
[25]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.地球物理学报,1995,38(5):599~607Sun R M,Liu F T.Crust structure and strong earthquake in Beijing,Tianjin,Tangshan area:Ⅰ.P wave velocity structure.Chinese J.Geophys.(in Chinese),1995,38(5):599~607
[26]孙若昧,赵燕来,吴丹.京津唐地区地壳结构与强震的发生—Ⅱ.S波速度结构.地球物理学报,1996,39(3):347~355Sun R M,Zhao Y L,Wu D.Crust structure and strong earthquake inBeijing,Tianjin,Tangshan area:Ⅱ.S wave velocity structure.Chinese J.Geophys.(in Chinese),1996,39(3):347~355
[27]Huang J,Zhao D.Crustal heterogeneity and seismotectonics of theregion around Beijing,China.Tectonophysics,2004,385:159~180
[28]Sun R,Liu F,He J,et al.Structural setting of strong earthquakes inthe Huabei area of China.Pure Appl.Geophys.,2001,158:903~918
[29]Zhao D,Tani H,Mishra O.Crustal heterogeneity in the 2000 westernTottori earthquake region:effect of fluids from slab dehydration.Phys.Earth Planet.Inter.,2004,145:161~177
[30]Johnson P,McEvilly T.Parkfield seismicity:Fluid-driven?J.Geophys.Res.,1995,100:12937~12950
[31]徐常芳.中国大陆壳内与上地幔高导层成因及唐山地震机理研究.地学前缘,2003,10:101~111Xu C F.The cause of formation of the upper mantle and crust highconductive layers in Chinese mainland and the study of Tangshanearthquake.Earth Science Frontiers,2003,10:101~111
[32]Hickman S,Sibson R,Bruhn R.Introduction to special section:Mechanical involvement of fluids in faulting.J.Geophys.Res.,1995,100:12831~12840
[33]Tian Y,Zhao D,Teng J.Deep structure of Southern California.Phys.Earth Planet.Inter.,2007,In press
[34]Kayal J,Zhao D,Mishra O,et al.The 2001 Bhuj earthquake:Tomographic evidence for fluids at the hypocenter and its implicationsfor rupture nucleation.Geophys.Res.Lett.,2002,29(24):2152~2155
[35]Nakajima J,Matsuzawa T,Hasegawa A,Zhao D.Seismic imaging ofarc magma and fluids under the central part of northeastern Japan.Tectonophysics,2001,341:1~17
[36]Zhao D,Todo S,Lei J.Local earthquake reflection tomography of theLanders aftershock area.Earth Planet.Sci.Lett.,2005,235:623~631
[37]Wessel P,Smith W.New,improved version of the generic mappingtools released.EOS,1998,79:579
[2]滕吉文.地球内部物质、能量交换与资源和灾害.地学前缘,2001,8(3):1~8Teng J W.The exchange of substance and energy,different spherecoupling and deep dynamical process within the earth.Earth ScienceFrontiers,2001,8(3):1~8
[3]Sieh K,Jones E,Hauksson E,et al.Near-field investigations of theLanders earthquake sequence April to July 1992.Science,1993,260:171~176
[4]Zhao D,Kanamori H.The 1992 Landers earthquake sequence:earthquake occurrence and structural heterogeneities.Geophys.Res.Lett.,1992,19:1~4
[5]刘福田,李强,吴华等.用于速度图像重建的层析成像方法.地球物理学报,1989,32(1):46~61Liu F T,Li Q,Wu H,et al.Tomographical method used to imagereconstruction.Chinese J.Geophys.(Acta Geophysica Sinica)(inChinese),1989,32(1):46~61
[6]赵文津,薛光琦,吴珍汉等.西藏高原上地幔的精细结构与构造-地震层析成像给出的启示.地球物理学报,2004,47(3):449~455Zhao W J,Xue G Q,Wu S H,et al.Fine velocity structure of theupper mantle beneath thee Xizang Plateau from tomography and itsgeological interpretations.Chinese J.Geophys.(in Chinese),2004,47(3):449~455
[7]裴顺平,许忠淮,汪素云等.新疆及临区Pn速度层析成像.地球物理学报,2002,45(2):218~225Pei S P,Xu Z H,Wang S Y,et al.Pn velocity tomography ofXinjiang,China and adjacent region.Chinese J.Geophys.(inChinese),2002,45(2):218~225
[8]李志伟,胥颐,郝天珧等.环渤海地区的地震层析成像与地壳上地幔结构.地球物理学报,2006,49(3):797~804Li Z W,Xu Y,Hao T Y,et al.Seismic tomography and velocitystructure in the crust and upper mantle around Bohai Sea area.Chinese J.Geophys.(in Chinese),2006,49(3):797~804
[9]王夫运,张先康,陈棋福等.北京地区上地壳三维细节构层析成像.地球物理学报,2005,48(2):359~366Wang F Y,Zhang X K,Chen Q F,et al.Fine tomographic inversionof the upper crust 3D structure around Beijing.Chinese J.Geophys.(in Chinese),2005,48(2):359~366
[10]Zhao D,Hasegawa A,Horiuchi S.Tomographic imaging of P and Swave velocity structure beneath Northeastern Japan.J.Geophys.Res.,1992,97:19909~19928
[11]Zhao D,Hasegawa A,Kanamori H.Deep structure of Japansubduction zone as derived from local,regional and teleseismicevents.J.Geophys.Res.,1994,99:22313~22329
[12]Um J,Thurber C.A fast algorithm for two-point seismic ray tracing.Bull.Seism.Soc.Am.,1987,77:972~986
[13]Paige C,Saunders M.LSQR:An algorithm for sparse linear equationsand sparse least squares.Assoc.Comput.Mach Trans.Math.Software,1982,8:43~71
[14]Christensen N.Poisson’s ratio and crustal seismology.J.Geophys.Res.,1996,101:3139~3156
[15]Zhao D,Kanamori H,Negishi H.Tomography of the source area ofthe 1995 Kobe earthquake:evidence for fluids at the hypocenter?Science,1996,274:1891~1894
[16]Zhao D,Ochi F,Hasegawa A,Yamamoto A.Evidence for the locationand cause of large crustal earthquakes in Japan.J.Geophys.Res.,2000,105:13579~13594
[17]Zhao D,Mishra O,Sanda R.Influence of fluids and magma onearthquakes:seismological evidence.Phys.Earth Planet.Inter.,2002,132:249~267
[18]Humphreys E,Clayton R.Adaptation of back projection tomographyto seismic travel time problems.J.Geophys.Res.,1988,93:1073~1085
[19]黄金莉,赵大鹏,郑斯华.川滇活动构造区地震层析成像.地球物理学报,2001,44:127~135Huang J L,Zhao D P,Zheng S H.Seismic tomography of theSichuan-Yunnan activity tectonic region.Chinese J.Geophys.(inChinese),2001,44:127~135
[20]Eberhart-Phillips D.Three-dimensional velocity structure in NorthernCalifornia coast ranges from inversion of local earthquake arrivaltimes.Bull.Seismol.Soc.Am.,1986,76(4):1025~1052
[21]Kanamori H,Hadley D.Crustal structure and temporal velocitychange in Southern California.Pure and Appl.Geophys.,1975,113:257~280
[22]Lees J,Malin P.Tomographic images of P-wave velocity variations atParkfield,California.J.Geophys.Res.,1990,95:21793~21804
[23]Michade A,Eberhart-Plillips D.Relations among fault behavior,subsurface geology,and three-dimensional velocity models.Science,1991,253:651~654
[24]滕吉文,张秉铭,胡家富等.地震“孕育”的深部介质和构造环境研究.见:陈运泰主编.中国地震学研究进展-庆贺谢毓寿教授八十寿辰.北京:地震出版社,1997,258~265Teng J W,Zhang B M,Hu J F,et al.The research of deep mediumand structural environment of earthquake“pregnancy”.In:Chen Y Ted.Advances in Seismology in China:In Honour of Professor XieYushou’s 80th Birthday.Beijing:Seismological Press,1997.258~265
[25]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.地球物理学报,1995,38(5):599~607Sun R M,Liu F T.Crust structure and strong earthquake in Beijing,Tianjin,Tangshan area:Ⅰ.P wave velocity structure.Chinese J.Geophys.(in Chinese),1995,38(5):599~607
[26]孙若昧,赵燕来,吴丹.京津唐地区地壳结构与强震的发生—Ⅱ.S波速度结构.地球物理学报,1996,39(3):347~355Sun R M,Zhao Y L,Wu D.Crust structure and strong earthquake inBeijing,Tianjin,Tangshan area:Ⅱ.S wave velocity structure.Chinese J.Geophys.(in Chinese),1996,39(3):347~355
[27]Huang J,Zhao D.Crustal heterogeneity and seismotectonics of theregion around Beijing,China.Tectonophysics,2004,385:159~180
[28]Sun R,Liu F,He J,et al.Structural setting of strong earthquakes inthe Huabei area of China.Pure Appl.Geophys.,2001,158:903~918
[29]Zhao D,Tani H,Mishra O.Crustal heterogeneity in the 2000 westernTottori earthquake region:effect of fluids from slab dehydration.Phys.Earth Planet.Inter.,2004,145:161~177
[30]Johnson P,McEvilly T.Parkfield seismicity:Fluid-driven?J.Geophys.Res.,1995,100:12937~12950
[31]徐常芳.中国大陆壳内与上地幔高导层成因及唐山地震机理研究.地学前缘,2003,10:101~111Xu C F.The cause of formation of the upper mantle and crust highconductive layers in Chinese mainland and the study of Tangshanearthquake.Earth Science Frontiers,2003,10:101~111
[32]Hickman S,Sibson R,Bruhn R.Introduction to special section:Mechanical involvement of fluids in faulting.J.Geophys.Res.,1995,100:12831~12840
[33]Tian Y,Zhao D,Teng J.Deep structure of Southern California.Phys.Earth Planet.Inter.,2007,In press
[34]Kayal J,Zhao D,Mishra O,et al.The 2001 Bhuj earthquake:Tomographic evidence for fluids at the hypocenter and its implicationsfor rupture nucleation.Geophys.Res.Lett.,2002,29(24):2152~2155
[35]Nakajima J,Matsuzawa T,Hasegawa A,Zhao D.Seismic imaging ofarc magma and fluids under the central part of northeastern Japan.Tectonophysics,2001,341:1~17
[36]Zhao D,Todo S,Lei J.Local earthquake reflection tomography of theLanders aftershock area.Earth Planet.Sci.Lett.,2005,235:623~631
[37]Wessel P,Smith W.New,improved version of the generic mappingtools released.EOS,1998,79:579
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心