用PKIKP的前驱震相探测青藏高原东部地幔底部的散射体
摘要
在兰州CTBTO地震台阵的记录波形上识别了PKIKP的前驱震相,并提取了它们的慢度、方位角及其与PKIKP之间的到时差,然后使用这些观测特征量测定了产生这些前驱震相的散射体的位置.结果表明,这些散射体分布在青藏高原东部及附近地区的地幔底部或D"区域,为该处结构的复杂不均匀性提供了证据.对比表明,这些散射体与全球层析成像在该处地幔底部给出的波速高异常区相关,可以合理地解释散射体的成因.这是因为研究表明,该处地幔底部的这些波速高异常区,很可能是古特提斯俯冲板块在青藏高原东部及附近地区到达地幔底部,并在俯冲过程中因拆沉、滞留及与地幔物质混合等作用所产生的不均匀体(也即地震波散射体)的显示.
引文
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2Gutenberg B,Richter C F.On seismic waves:I,Gerlands Beitr Geophysik.1934,43:56—133
3Gutenberg B.The boundary of the Earth’s inner core.Eos Trans AGU,1957,38:750—753
4Bullen K E,Burke-Gaffney T N.Diffracted seismic waves near the PKP caustic.Geophys J Int.,1958,1:9—17
5Bolt B A.Gutenberg’s early PKP observations.Nature,1962,196:122—124
6Sacks I S,Saa G.The structure of the transition zone between the inner core and the outer core.Year Book Carnegie Inst Washington,1969,69:419—426
7Haddon R A W.Corrugations on the CMB or transition layers between inner and outer coresAbstract,Eos Trans AGU,1972,53:600
8Cleary J R,Haddon R A W.Seismic wave scattering near the core-mantle boundary:A new interpretation of precursors to PKP.Nature,1972,240:549—551
9Doornbos D J,Husebye E S.Array analysis of PKP phases and their precursors.Phys Earth Planet Inter,1972,5:387—399
10King D W,Haddon R A W,Cleary J R.Array analysis of precursors to PKIKP,in the distance range128o to142o.Geophys J R Astron Soc,1974,37:157—173
11Husebye E S,King D W,Haddon R A W.Precursor to PKIKP and seismic wave scattering near the mantle-core boundary.J Geophys Res,1976,81:1870—1882
12Doornbos D J.Characteristics of lower mantle inhomogeneities from scattered waves.Geophys J R Astron Soc,1976,49:541—542
13Hedlin M A H,Shearer P M,Earle P S.Seismic evidence for small-scale heterogeneity throughout the Earth’s mantle.Nature,1997,387:145—150
14Cormier V.Anisotropy of heterogeneity scale lengths in the lower mantle from PKIKP precursors.Geophys J Int,1999,136:373—384
15Margerin L,Nolet G.Multiple scattering of high-frequency seismic waves in the deep Earth:PKP precursor analysis and inversion for mantle granularity.J Geophys Res,2003,108(B5):2234,doi:10.1029/2002JB001974
16Wen L.Intense seismic scattering near the Earth’s core-mantle boundary beneath the Comoros hotspot.Geophys Res Lett,2000,27:3627—3630
17Niu F,Wen L.Strong seismic scatterers near the core-mantle boundary west of Mexico.Geophys Res Lett,2001,28:3557—3560
18Shen Y,Blum J.Seismic evidence for accumulated oceanic crust above the660-km discontinuity beneath southern Africa.Geophys Res Lett,2003,30:1925,doi:10.1029/2003GL017991
19Shen X,Zhou H,Kawakatsu H.Mapping the upper mantle discontinuities beneath China with teleseismic re-ceiver functions.Earth Planets Space,2008,60:713—719
20沈旭章,周蕙兰.接收函数CCP-PWS偏移方法探测东北地区620km深处低速层.科学通报,2009,54:215—223
21Richards A,Engebretson,D C.Large-scale mantle convection and the history of subduction.Nature,1992,355:437—440
22Grand P S.Mantle shear-wave tomography and the fate of subducted slabs.Phil Trans R Soc Lond A,2001,360:2475—2491
23van der Hilst R D,Widiyantoro S,Engdahl E R.Evidence for deep mantle circulation from global tomography.Nature,1997,386:578—584
24Bijwaard H,Spakman W,Engdahl E R.Closing the gap between regional and global travel time tomography.J Geophys Res,1998,103:30055—30078
25Cao A,Romanowicz B.Locating scatterers in the mantle using array analysis of PKIKP precursors from an earthquake doublet.Earth Planet Sci Lett,2007,255:22—31
26郝春月,郑重,郭燕平,等.中国数字地震台网(CDSN)和IMS/PS台阵的监测定位能力评估.地震地磁观测与研究,2006,27:56—63
27许健生,李建,刘旭,等.兰州大尖山台阵建设.西北地震学报,2005,27(增刊):27—30
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29Kennett B L N,Engdahl E R.Travel times for global earthquake location and phase identification.Geophys J Int,1991,105:429—465
30Muirhead K J,Datt R.The Nth root process applied to seismic array data.Geophys J R Astron Soc,1976,47:197—210
31Capon J.High-resolution frequency-wavenumber spectrum analysis.Proc IEEE,1969,57:1408—1418
32Gupta I N,Lynnes C S,Wagner R A.Broadband F-K analysis of array data to identify sources of local scattering.Geophys Res Lett,1990,17:183—186
33Goldstein P.Deterministic frequency wavenumber methods and direct measurements of rupture propagation during earthquakes using a dense array:Theory and methods.J Geophys Res,1991,96:6173—6185
34Cormier V.Time domain modeling of PKIKP precursor for constraints on the heterogeneity in the lowermost mantle.Geophys J Int,1995,121:725—736
35任继舜,等.从全球看中国大地构造-中国及邻区大地构造图简要说明.北京:地质出版社,2003.26—34
36Hafkenscheid E,Wortel M J R,Spakman W.Subduction history of the Tethyan region derived from seismic to-mography and tectonic reconstructions.J Geophys Res,2006,111:B08401,doi:10.1029/2005JB003791
37Wessel P,Smith W H F.New version of the generic mapping tools released.Eos Trans Am Geophys Union,1995,76:329
2Gutenberg B,Richter C F.On seismic waves:I,Gerlands Beitr Geophysik.1934,43:56—133
3Gutenberg B.The boundary of the Earth’s inner core.Eos Trans AGU,1957,38:750—753
4Bullen K E,Burke-Gaffney T N.Diffracted seismic waves near the PKP caustic.Geophys J Int.,1958,1:9—17
5Bolt B A.Gutenberg’s early PKP observations.Nature,1962,196:122—124
6Sacks I S,Saa G.The structure of the transition zone between the inner core and the outer core.Year Book Carnegie Inst Washington,1969,69:419—426
7Haddon R A W.Corrugations on the CMB or transition layers between inner and outer coresAbstract,Eos Trans AGU,1972,53:600
8Cleary J R,Haddon R A W.Seismic wave scattering near the core-mantle boundary:A new interpretation of precursors to PKP.Nature,1972,240:549—551
9Doornbos D J,Husebye E S.Array analysis of PKP phases and their precursors.Phys Earth Planet Inter,1972,5:387—399
10King D W,Haddon R A W,Cleary J R.Array analysis of precursors to PKIKP,in the distance range128o to142o.Geophys J R Astron Soc,1974,37:157—173
11Husebye E S,King D W,Haddon R A W.Precursor to PKIKP and seismic wave scattering near the mantle-core boundary.J Geophys Res,1976,81:1870—1882
12Doornbos D J.Characteristics of lower mantle inhomogeneities from scattered waves.Geophys J R Astron Soc,1976,49:541—542
13Hedlin M A H,Shearer P M,Earle P S.Seismic evidence for small-scale heterogeneity throughout the Earth’s mantle.Nature,1997,387:145—150
14Cormier V.Anisotropy of heterogeneity scale lengths in the lower mantle from PKIKP precursors.Geophys J Int,1999,136:373—384
15Margerin L,Nolet G.Multiple scattering of high-frequency seismic waves in the deep Earth:PKP precursor analysis and inversion for mantle granularity.J Geophys Res,2003,108(B5):2234,doi:10.1029/2002JB001974
16Wen L.Intense seismic scattering near the Earth’s core-mantle boundary beneath the Comoros hotspot.Geophys Res Lett,2000,27:3627—3630
17Niu F,Wen L.Strong seismic scatterers near the core-mantle boundary west of Mexico.Geophys Res Lett,2001,28:3557—3560
18Shen Y,Blum J.Seismic evidence for accumulated oceanic crust above the660-km discontinuity beneath southern Africa.Geophys Res Lett,2003,30:1925,doi:10.1029/2003GL017991
19Shen X,Zhou H,Kawakatsu H.Mapping the upper mantle discontinuities beneath China with teleseismic re-ceiver functions.Earth Planets Space,2008,60:713—719
20沈旭章,周蕙兰.接收函数CCP-PWS偏移方法探测东北地区620km深处低速层.科学通报,2009,54:215—223
21Richards A,Engebretson,D C.Large-scale mantle convection and the history of subduction.Nature,1992,355:437—440
22Grand P S.Mantle shear-wave tomography and the fate of subducted slabs.Phil Trans R Soc Lond A,2001,360:2475—2491
23van der Hilst R D,Widiyantoro S,Engdahl E R.Evidence for deep mantle circulation from global tomography.Nature,1997,386:578—584
24Bijwaard H,Spakman W,Engdahl E R.Closing the gap between regional and global travel time tomography.J Geophys Res,1998,103:30055—30078
25Cao A,Romanowicz B.Locating scatterers in the mantle using array analysis of PKIKP precursors from an earthquake doublet.Earth Planet Sci Lett,2007,255:22—31
26郝春月,郑重,郭燕平,等.中国数字地震台网(CDSN)和IMS/PS台阵的监测定位能力评估.地震地磁观测与研究,2006,27:56—63
27许健生,李建,刘旭,等.兰州大尖山台阵建设.西北地震学报,2005,27(增刊):27—30
28许健生,赵仪全,苏向州,等.兰州大尖山地震台阵勘址.地震地磁观测与研究,2006,27:51—57
29Kennett B L N,Engdahl E R.Travel times for global earthquake location and phase identification.Geophys J Int,1991,105:429—465
30Muirhead K J,Datt R.The Nth root process applied to seismic array data.Geophys J R Astron Soc,1976,47:197—210
31Capon J.High-resolution frequency-wavenumber spectrum analysis.Proc IEEE,1969,57:1408—1418
32Gupta I N,Lynnes C S,Wagner R A.Broadband F-K analysis of array data to identify sources of local scattering.Geophys Res Lett,1990,17:183—186
33Goldstein P.Deterministic frequency wavenumber methods and direct measurements of rupture propagation during earthquakes using a dense array:Theory and methods.J Geophys Res,1991,96:6173—6185
34Cormier V.Time domain modeling of PKIKP precursor for constraints on the heterogeneity in the lowermost mantle.Geophys J Int,1995,121:725—736
35任继舜,等.从全球看中国大地构造-中国及邻区大地构造图简要说明.北京:地质出版社,2003.26—34
36Hafkenscheid E,Wortel M J R,Spakman W.Subduction history of the Tethyan region derived from seismic to-mography and tectonic reconstructions.J Geophys Res,2006,111:B08401,doi:10.1029/2005JB003791
37Wessel P,Smith W H F.New version of the generic mapping tools released.Eos Trans Am Geophys Union,1995,76:329
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