南海中北部陆缘横波速度结构及其构造意义
摘要
纵横波联合勘探可以得到更多关于岩石圈层岩性、物性等介质属性方面的信息,有效提高地壳物质组成的约束性.在纵波速度结构模型的基础上,通过射线追踪和走时拟合对OBS2006-3地震剖面径向分量的转换震相进行了横波速度结构模拟.结果表明:沉积层1、沉积层2的横波速度分别为0.7～0.9 km/s和1.6～1.7 km/s,波速比由2.64～3.16变化到2.41左右,较高的波速比表明沉积层固结程度不高;中生代沉积层横波速度由浅部的2.6 km/s增大到3.0 km/s,波速比为1.74～1.80;地壳中波速比为1.74～1.82,表明该剖面地壳为陆壳性质;下地壳高速层的横波速度为4.0～4.2 km/s,纵横波速比为1.73～1.78,揭示高速层的物质组成为铁镁质的基性岩,推断其与海底扩张停止之后的岩浆底侵作用有关.
The joint exploration of P-wave and S-wave can obtain amount of information on lithology and geophysical properties,which effectively improve the composition constraint of the deep crustal structure.Based on the optimum P-wave model,the shear waves recorded on the radial components of profile OBS2006-3 have been modeled by 2-D ray-tracing.The S-wave velocities in sedimentary layer 1 and sedimentary layer 2 are of 0.7～0.9 km/s and 1.6～1.7 km/s, respectively.The V_p/V_s ratios in these sediments vary from 2.64～3.16 to 2.41.The relatively high V_p/V_s ratios are probably related to unconsolidated sediments.In the Mesozoic sedimentary layer,the S-wave velocity increases gradually from 2.6 km/s at the top to 3.0 km/s at the bottom,and the V_p/V_s ratio is of 1.71～1.80.The V_p/V_s ratio of 1.74～1.82 in the crust is considered to be the continental crust.The S-wave velocity and V_p/V_s are 4.0～4.2 km/s and 1.73～1.78 of the High Velocity Layer(HVL) in the lower crust,which suggest that the HVL has a mafic composition that may originate from underplating of the igneous rocks after the cessation of the seafloor spreading.
The joint exploration of P-wave and S-wave can obtain amount of information on lithology and geophysical properties,which effectively improve the composition constraint of the deep crustal structure.Based on the optimum P-wave model,the shear waves recorded on the radial components of profile OBS2006-3 have been modeled by 2-D ray-tracing.The S-wave velocities in sedimentary layer 1 and sedimentary layer 2 are of 0.7～0.9 km/s and 1.6～1.7 km/s, respectively.The V_p/V_s ratios in these sediments vary from 2.64～3.16 to 2.41.The relatively high V_p/V_s ratios are probably related to unconsolidated sediments.In the Mesozoic sedimentary layer,the S-wave velocity increases gradually from 2.6 km/s at the top to 3.0 km/s at the bottom,and the V_p/V_s ratio is of 1.71～1.80.The V_p/V_s ratio of 1.74～1.82 in the crust is considered to be the continental crust.The S-wave velocity and V_p/V_s are 4.0～4.2 km/s and 1.73～1.78 of the High Velocity Layer(HVL) in the lower crust,which suggest that the HVL has a mafic composition that may originate from underplating of the igneous rocks after the cessation of the seafloor spreading.
引文
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[7]Yan P,Zhou D,Liu Z S.A crustal structure profile across the northern continental margin of the South China Sea. Tectonophysics,2001.338(1):1-21
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[12]Zhao M H,Qiu X L,Xia S H,et al.Seismic structure in the northeastern South China Sea:S-wave velocity and V_p/V_s ratios derived from three-component OBS data.Tectonophysics, 2010,480(1-4):183-197
[13]Zhang Z J.Zhang X,Badal J.Composition of the crust beneath southeastern China derived from an integrated geophysical data set.J.Geophys.,2006,113:B04417
[14]赵兵,张素芳.李守林.琼东南盆地区的地壳密度与岩石结构.地球物理学报,2011,54(1):98-107 Zhao B,Zhang S F,Li S L.Crustal density and composition models beneath Qiongdongnan basin.Chinese J.Geophys. (in Chinese),2011,54(1):98-107
[15]Christensen N I,Mooney W D.Seismic velocity structure and composition of the continental crust;A global view.J. Geophys.Res.,1995,100(B6):9761-9788
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[18]赵中贤,周蒂,廖杰等.珠江口盆地陆架区岩石圈伸展模拟及裂后沉降分析.地质学报,2010,84(8):1135-1145 Zhao Z X,Zhou D,Liao J,et al.Lithospheric stretching modeling of the continental shelf in the Pearl River Mouth Basin and analysis of post-breakup subsidence.Acta Geologica Sinica(in Chinese),2010,84(8):1135-1145
[19]卫小冬,阮爱国,赵明辉等.穿越东沙隆起和潮汕坳陷的OBS广角地震剖面.地球物理学报,2011,54(12):3325- 3335 Wei X D,Ruan A G,Zhao M H,et al.A wide-angle OBS profile across Dongsha Rise and Chaoshan Depression in the northern South China Sea.Chinese J.Geophys.(in Chinese),2011,54(12):3325-3335
[20]卫小冬,赵明辉,阮爱国等.南海中北部OBS2006-3地震剖面中横波的识别与应用.热带海洋学报,2010,29(5):72-80 Wei X D,Zhao M H,Ruan A G,et al.Identification and application of shear waves along the profile OBS2006-3 in the mid-northern South China Sea.Journal of Tropical Oceanography(in Chinese),2010,29(5):72-80
[21]Digrances P,Mjelde R,Kodaira S,et al.A regional shearwave velocity model in the central Voring Basin,N.Norway, using three-component Ocean Bottom Seismographs. Tectonophysics,1998,293(3-4):157-174
[22]Kodaira S,Bellenberg M,Iwasaki T,et al.V_p/V_s ratio structure of the Lofoten continental margin,northern Norway,and its geological implications.Geophys.J.Int., 1996,124(3):724-740
[23]邵磊,尤洪庆,郝沪军等.南海东北部中生界岩石学特征及沉积环境.地质论评,2007,53(2):164-169 Shao L,You H Q,Hao H J,et al.Petrology and depositional environments of Mesozoic strata in the Northeastern South China Sea.Geological Review(in Chinese),2007,53(2):164-169
[24]Holbrook W,Mooney W,Christensen N.The seismic velocity structure of the deep continental crust.In:Fountain D M,Arculus R,Kay R W,eds.Continental Lower Crust. Development in Geotectonics,1992,23;1-43
[25]Zelt C A,Smith R B.Seismic traveltime inversion for 2-D crustal velocity structure.Geophys.J.Int.,1992,108(1); 16-34
[26]罗文造,阎贫,温宁等.南海北部潮汕坳陷海区海底地震仪调查实验.热带海洋学报,2009,28(4):59-65 Luo W Z,Yan P,Wen N,et al.Ocean-bottom seismometer experiment over Chaoshan Sag in the northern South China Sea.Journal of Tropical Oceanography(in Chinese), 2009,28(4):59-65
[27]姚伯初.南海北部陆缘的地壳结构及构造意义.海洋地质与第四纪地质,1 998,18(2):1-16 Yao B C.Crust structure of the northern margin of the south China sea and its tectonic significance.Marine Geology & Quaternary Geology(in Chinese),1998,18(2):1-16
[28]阎全人,王宗起,李赠悦等.南海北部陆缘地壳结构特征及其构造过程.地质论评,2000,46(4):417-423 Yan Q R,Wang Z Q,Li Z Y,et al.Crustal structure of the northern margin of the south China sea and its tectonic processes since the Cretaceous.Geological Review(in Chinese),2000,46(4):417-423
[29]阎贫,刘海龄.南海北部陆缘地壳结构探测结果分析.热带海洋学报,2002,21(2):1-12 Yan P,Liu H L.Analysis on deep crust sounding results in northern margin of South China Sea.Journal of Tropical Oceanography(in Chinese),2002,21(2):1-12
[30]张中杰,刘一峰,张素芳等.南海北部珠江口琼东南盆地地壳速度结构与几何分层.地球物理学报,2009,52(10): 2461-2471 Zhang Z J,LiuY F,Zhang S F,etal.CrustalP-wave velocitystructureand layering beneath Zhujiangkou-Qiongdongnan basins,the northern continental margin of South China Sea.Chinese J.Geophys(in Chinese),2009, 52(10):2461-2471
[31]Carlson R L,Milier D J.A new assessment of the abundance of serpentinite in the oceani ccrust.Geophysical Research Letters,1997,24(4):457-460
[32]Rudnick R L,Fountain D M.Nature and composition of the continental crust;A lower crustal perspective.Rev.Geophys, 1995,33(3):267-309
[33]刘明军,李松林,方盛明等.利用地震波速研究青藏高原东北缘地壳组成及其动力学.地球物理学报,2008,51(2): 412-430 Liu M J,Li X L,Fang S M,et al.Study on crustal composition and geodynamics using seismic velocities in the northeastern margin of the Tibetan Plateau.Chinese J. Geophys.(in Chinese),2008,51(2):412-430
[34]Liu M J,MooneyW,Li S L.Crustal structure of the northeastern margin of the Tibetan plateau from the Songpan-Ganzi terrane to the Ordos basin.Tectonophysics,2006,420 (1-2):253-266
[35]Chian D,Louden K E.The continent-ocean crustal transition across the southwest Greenland margin.J.Geophys.Res., 1994,99(B5):9117-9135
[36]L(u|¨)dmann T,Wong H K.Neotectonic regime on the passive continental margin of the northern South China Sea. Tectonophysics,1999,311(1-4):113-138
[2]郝天珧,黄松,徐亚等.南海东北部及邻区深部结构的综合地球物理研究.地球物理学报,2008,51(6):1785- 1796 Hao T Y,Huang S,Xu Y,et al.Comprehensive geophysical research on the deep structure of Northeastern South China Sea.Chinese J.Geophys.(in Chinese),2008.51(6):1785-1796
[3]Taylor B,Hayes D E.Origin and history of the South China Sea Basin.In:Hayes D E,ed.The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands.Geophysical Monograph,AGU,Washington,DC,1983,27
[4]姚伯初,曾维军,陈艺中等.南海北部陆缘东部的地壳结构. 地球物理学报,1994,37(1):27-35 Yao B C,Zeng W J,Chen Y Z,et al.The crustal structure in the eastern part of the northern margin of the south China sea.Chinese J.Geophys.(in Chinese),1994,37(1),27- 35
[5]Nissen S S,Hayes D E,Buhl P,et al.Deep penetration seismic soundings across the northern margin of the South China Sea.J.Geophys.Res.,1995,100(B11):22407- 22433
[6]Qiu X L,Ye S Y,Wu S M,et al.Crustal structure across the Xisha Trough,northwestern South China Sea.Tectonophysics, 2001,341(1-4):179-193
[7]Yan P,Zhou D,Liu Z S.A crustal structure profile across the northern continental margin of the South China Sea. Tectonophysics,2001.338(1):1-21
[8]丘学林,施小斌,阎贫等.南海北部地壳结构的深地震探测和研究新进展.自然科学进展,2003,13(3):231-236 Qiu X L,Shi X B,Yan P,et al.Recent progress of deep seismic experiments and studies of crustal structure in northern South China Sea.Progress in Natural Science(in Chinese),2003,13(7):481-488
[9]Wang T K,Cheng M K,Lee C S,et al.Seismic imaging of the transitional crust across the northeastern margin of the South China Sea.Tectonophysics,2006,412(3-4):237- 254
[10]阎贫.海底地震仪记录中的横波.海洋地质与第四纪地质,1998,18(1):115-118 Yan P.Shear waves in OBS's records.Marine Geology & Quaternary Geology(in Chinese),1998,18(1):115-118
[11]赵明辉,丘学林,夏少红等.南海东北部三分量海底地震仪记录中横波的识别和分析.自然科学进展,2007,17(11): 1516-1523 Zhao M H,Qiu X L,Xia S H,et al.Identification and analysis of shear waves recorded by three-component OBSs in northeastern South China Sea.Progress in Natural Science (in Chinese),2007,18(2):181-188
[12]Zhao M H,Qiu X L,Xia S H,et al.Seismic structure in the northeastern South China Sea:S-wave velocity and V_p/V_s ratios derived from three-component OBS data.Tectonophysics, 2010,480(1-4):183-197
[13]Zhang Z J.Zhang X,Badal J.Composition of the crust beneath southeastern China derived from an integrated geophysical data set.J.Geophys.,2006,113:B04417
[14]赵兵,张素芳.李守林.琼东南盆地区的地壳密度与岩石结构.地球物理学报,2011,54(1):98-107 Zhao B,Zhang S F,Li S L.Crustal density and composition models beneath Qiongdongnan basin.Chinese J.Geophys. (in Chinese),2011,54(1):98-107
[15]Christensen N I,Mooney W D.Seismic velocity structure and composition of the continental crust;A global view.J. Geophys.Res.,1995,100(B6):9761-9788
[16]Christensen N I.Poisson's ratio and crustal seismology.J. Geophys.Res.,1996,101(B2).3139-3156
[17]黄慈流.南海及围区大地构造格架与沉积盆地分布.见:龚再升,李思田,夏戡原等主编.南海北部大陆边缘盆地分析与油气聚集.北京:科学出版社,1997.44-51 Huang C L.Tectonic framework and distribution of basins in the South China Sea and adjacent areas.In:Gong Z S,Li S T,Xia K Y,et al,eds.Basin Analysis and Hydrocarbon Accumulation in the North Continent Margin of the South China Sea(in Chinese).Beijing:Science Press.1997.44- 51
[18]赵中贤,周蒂,廖杰等.珠江口盆地陆架区岩石圈伸展模拟及裂后沉降分析.地质学报,2010,84(8):1135-1145 Zhao Z X,Zhou D,Liao J,et al.Lithospheric stretching modeling of the continental shelf in the Pearl River Mouth Basin and analysis of post-breakup subsidence.Acta Geologica Sinica(in Chinese),2010,84(8):1135-1145
[19]卫小冬,阮爱国,赵明辉等.穿越东沙隆起和潮汕坳陷的OBS广角地震剖面.地球物理学报,2011,54(12):3325- 3335 Wei X D,Ruan A G,Zhao M H,et al.A wide-angle OBS profile across Dongsha Rise and Chaoshan Depression in the northern South China Sea.Chinese J.Geophys.(in Chinese),2011,54(12):3325-3335
[20]卫小冬,赵明辉,阮爱国等.南海中北部OBS2006-3地震剖面中横波的识别与应用.热带海洋学报,2010,29(5):72-80 Wei X D,Zhao M H,Ruan A G,et al.Identification and application of shear waves along the profile OBS2006-3 in the mid-northern South China Sea.Journal of Tropical Oceanography(in Chinese),2010,29(5):72-80
[21]Digrances P,Mjelde R,Kodaira S,et al.A regional shearwave velocity model in the central Voring Basin,N.Norway, using three-component Ocean Bottom Seismographs. Tectonophysics,1998,293(3-4):157-174
[22]Kodaira S,Bellenberg M,Iwasaki T,et al.V_p/V_s ratio structure of the Lofoten continental margin,northern Norway,and its geological implications.Geophys.J.Int., 1996,124(3):724-740
[23]邵磊,尤洪庆,郝沪军等.南海东北部中生界岩石学特征及沉积环境.地质论评,2007,53(2):164-169 Shao L,You H Q,Hao H J,et al.Petrology and depositional environments of Mesozoic strata in the Northeastern South China Sea.Geological Review(in Chinese),2007,53(2):164-169
[24]Holbrook W,Mooney W,Christensen N.The seismic velocity structure of the deep continental crust.In:Fountain D M,Arculus R,Kay R W,eds.Continental Lower Crust. Development in Geotectonics,1992,23;1-43
[25]Zelt C A,Smith R B.Seismic traveltime inversion for 2-D crustal velocity structure.Geophys.J.Int.,1992,108(1); 16-34
[26]罗文造,阎贫,温宁等.南海北部潮汕坳陷海区海底地震仪调查实验.热带海洋学报,2009,28(4):59-65 Luo W Z,Yan P,Wen N,et al.Ocean-bottom seismometer experiment over Chaoshan Sag in the northern South China Sea.Journal of Tropical Oceanography(in Chinese), 2009,28(4):59-65
[27]姚伯初.南海北部陆缘的地壳结构及构造意义.海洋地质与第四纪地质,1 998,18(2):1-16 Yao B C.Crust structure of the northern margin of the south China sea and its tectonic significance.Marine Geology & Quaternary Geology(in Chinese),1998,18(2):1-16
[28]阎全人,王宗起,李赠悦等.南海北部陆缘地壳结构特征及其构造过程.地质论评,2000,46(4):417-423 Yan Q R,Wang Z Q,Li Z Y,et al.Crustal structure of the northern margin of the south China sea and its tectonic processes since the Cretaceous.Geological Review(in Chinese),2000,46(4):417-423
[29]阎贫,刘海龄.南海北部陆缘地壳结构探测结果分析.热带海洋学报,2002,21(2):1-12 Yan P,Liu H L.Analysis on deep crust sounding results in northern margin of South China Sea.Journal of Tropical Oceanography(in Chinese),2002,21(2):1-12
[30]张中杰,刘一峰,张素芳等.南海北部珠江口琼东南盆地地壳速度结构与几何分层.地球物理学报,2009,52(10): 2461-2471 Zhang Z J,LiuY F,Zhang S F,etal.CrustalP-wave velocitystructureand layering beneath Zhujiangkou-Qiongdongnan basins,the northern continental margin of South China Sea.Chinese J.Geophys(in Chinese),2009, 52(10):2461-2471
[31]Carlson R L,Milier D J.A new assessment of the abundance of serpentinite in the oceani ccrust.Geophysical Research Letters,1997,24(4):457-460
[32]Rudnick R L,Fountain D M.Nature and composition of the continental crust;A lower crustal perspective.Rev.Geophys, 1995,33(3):267-309
[33]刘明军,李松林,方盛明等.利用地震波速研究青藏高原东北缘地壳组成及其动力学.地球物理学报,2008,51(2): 412-430 Liu M J,Li X L,Fang S M,et al.Study on crustal composition and geodynamics using seismic velocities in the northeastern margin of the Tibetan Plateau.Chinese J. Geophys.(in Chinese),2008,51(2):412-430
[34]Liu M J,MooneyW,Li S L.Crustal structure of the northeastern margin of the Tibetan plateau from the Songpan-Ganzi terrane to the Ordos basin.Tectonophysics,2006,420 (1-2):253-266
[35]Chian D,Louden K E.The continent-ocean crustal transition across the southwest Greenland margin.J.Geophys.Res., 1994,99(B5):9117-9135
[36]L(u|¨)dmann T,Wong H K.Neotectonic regime on the passive continental margin of the northern South China Sea. Tectonophysics,1999,311(1-4):113-138
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