Crustal Structure of the Northwest Sub-Basin of the South China Sea and Its Tectonic Implication
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摘要: 西北次海盆的深部地壳结构蕴含着南海北部陆缘拉张过程的重要信息.广角反射/折射测线(OBS2006-2)长386 km，是目前唯一的一条沿NEE向穿过西沙地块、并平行于西北次海盆扩张脊的深地震测线.通过射线追踪与走时模拟方法(RAYINVR)，获得了OBS2006-2测线下方的速度结构.结果表明：西沙地块的沉积层厚度约为1~2 km，而西北次海盆的沉积层厚度大约为2~3 km；Moho界面从西沙地块的27 km逐步抬升到西北次海盆的12 km，Moho界面下方的速度为7.8~8.0 km/s；未发现壳内高速层和低速层.在西沙地块和西北次海盆的过渡区，有着较大量的岩浆活动信息，推测与西北次海盆的初始扩张有关.OBS2006-2测线中114.5°E以西的地区为减薄的陆壳，而114.5°E以东的地区为洋壳，莫霍面在陆壳与洋壳的结合处剧烈抬升，地壳厚度明显减薄.西北次海盆的扩张脊下方可能有残余岩浆的存在.Abstract: Deep crustal structure in the northwest sub-basin contains the key information of the rifting process of the northern continental margin of the South China Sea (SCS). A 386 km-long seismic profile (OBS2006-2) with wide-angle reflective and refractive ocean bottom seismometer (OBS) data was acquired across Xisha block and the Northwest sub-basin (NW sub-basin) of the SCS in NEE direction, which is the only profile hitherto parallel to the expanding ridge of the NW sub-basin. The crustal structure along OBS2006-2 has been obtained by using ray-tracing simulation method (RAYINVR), which yields information on the velocities, tectonics, and geophysical properties. Our velocity structure indicates that sediment thickness increases from Xisha block (about 1-2 km) to NW sub-basin (about 2-3 km). Moho interface changes from typical continent margin of South China (~27 km) to oceanic crust (~12 km). The velocity at the top of upper mantle varies from 7.8 to 8.0 km/s. No high velocity layer and low velocity layer have been identified. Voluminous magmatism in transition zone between Xisha block and NW sub-basin, is possibly related to the initial extending of the NW sub-basin. The part of model in the domain of 220-370 km would be of oceanic crust while the western part in the domain of 0-220 km may be of thinned continental crust. Residual magma may exist under the speading ridge of the NW sub-basin deduced by the anomaly of Pn seismic phase.
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Key words:
- NW sub-basin /
- crustal structure /
- magmatism /
- douple-peak seamount /
- ocean bottom seismometer (OBS) /
- sedimentology /
- geophysics
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图 1 研究区水深及相邻地震测线布设位置(磁条带数据来自于Briais et al., 1993)
Fig. 1. Bathymetry of the research area and surrounding deployed seismic lines
图 2 OBS2006-2测线与MCS97303多道地震剖面双程走时对比
a.MCS97303多道地震剖面，据Li et al., 2008修改；b.OBS2006-2测线与MCS97303测线位置与界面对比；AA'和BB'分别对应OBS2006-2测线和MCS97303测线
Fig. 2. Comparison of twice way time of MCS97303 and OBS2006
图 3 OBS5台站地震记录剖面及射线追踪
a.OBS5台站垂直分量综合地震记录剖面，折合速度为6.0 km/s；b.实际观测走时与理论计算走时拟合结果；c.速度模型与射线追踪
Fig. 3. OBS5 seismic recording section and ray tracing simulation
图 4 OBS2台站地震记录剖面及射线追踪
a.OBS2台站垂直分量综合地震记录剖面，折合速度为6.0 km/s；b.实际观测走时与理论计算走时拟合结果；c.速度模型与射线追踪
Fig. 4. OBS2 seismic recording section and ray tracing simulation
图 5 OBS11台站地震记录剖面及射线追踪
a.OBS11台站垂直分量综合地震记录剖面，折合速度为6.0 km/s；b.实际观测走时与理论计算走时拟合结果；c.速度模型与射线追踪
Fig. 5. OBS11 seismic recording section and ray tracing simulation
图 6 OBS2006-2测线最终速度结构及自由空间重力异常
a.OBS2006-2的重力异常；b.OBS2006-2最终速度模型；c.一维速度结构
Fig. 6. The final velocity model of OBS2006-2 and its corresponding free-air gravity anomaly
图 7 OBS2006-2测线所有台站PmP及Pn震相的走时模拟
a.PmP和Pn震相覆盖情况；b.PmP和Pn震相走时模拟
Fig. 7. Ray tracing simulation for all PmP and Pn seismic phases
图 8 OBS2006-2测线速度结构的检测板测试
a.输入模型(加入±0.25 km/s的速度扰动)；b.输出模型(加入了射线覆盖)
Fig. 8. Checker board test for the final velocity model of OBS2006-2
图 9 SO49-25多道地震剖面(据丁巍伟等, 2009, SO49-25测线位置见图 1)
Fig. 9. Multi-channel seismic profile of SO49-25
表 1 OBS2006-2测线12个台站所有震相的射线追踪结果
Table 1. Ray tracing for all seismic phases recorded by total 12 OBSs
震相 拾取点数 追踪点数 百分比(%) RMS(s) χ2 Pdw 344 342 98.5 0.046 0.862 Pg 929 892 96.0 0.087 3.044 PmP 340 337 99.2 0.077 2.633 Pn 184 178 96.7 0.096 3.075 总计 1796 1739 96.8 0.079 2.529 注：该统计结果不包括OBS10号台站的Pn震相(41个点)；RMS为计算走时和观测走时残差的均方根值；χ2为卡方分布检测值，当χ2接近于1时拟合程度最好. 
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[1] Ao, W., Zhao, M.H., Qiu, X.L., et al., 2010. The correction of shot and OBS position in the 3D seismic experiment of the SW Indian Ocean ridge. Chinese J. Geophys. , 53(12): 2982-2991(in Chinese with English abstract). [2] Breivik, A.J., Faleide, J.I., Mjelde, R., et al., 2009. Magma productivity and early seafloor spreading rate correlation on the northern Vøring margin, Norway—constraints on mantle melting. Tectonophysics, 468(1-4): 206-223. doi: 10.1016/j.tecto.2008.09.020 [3] Briais, A., Patriat, P., Tapponnier, P., 1993. Updated interpretation of magnetic anomalies and seafloor spreading stages in the South China Sea: implications for the tertiary tectonics of Southeast Asia. J. Geophys. Res. , 98(B4): 6299-6328. doi: 10.1029/92JB02280 [4] Cande, S.C., Kent, D.V., 1995. Revised calibration of the geomagnetic polarity timescale for the Late Cretacous and Cenozoic. J. Geophys. Res. , 100(B4): 6093-6095. doi: 10.1029/94JB03098 [5] Clift, P., Lin, J., 2001. Preferential mantle lithospheric extension under the South China margin. Marine and Petroleum Geology, 18(8): 929-945. doi: 10.1016/S0264-8172(01)00037-X [6] Ding, W.W., Li, M.B., Zhao, L.H., et al., 2009. Cenozoic tectono-sedimentary characteristics and extension model of the north-west sub-basin, South China Sea. Earth Science Frontiers, 16(4): 147-156 (in Chinese with English abstract). http://www.cnki.com.cn/Article/CJFDTotal-GSFT201104004.htm [7] Hao, T.Y., Liu, J.H., Song, H.B., et al., 2002. Geophysical evidences of some important faults in South China and adjacent marginal seas region. Progress in Geophysics, 17(1): 13-23 (in Chinese with English abstract). http://www.researchgate.net/publication/288555249_Geophysical_evidences_of_some_important_faults_in_South_China_and_adjacent_marginal_seas_region [8] Hayes, D.E., Nissen, S.S., 2005. The South China Sea margins: implications for rifting contrasts. Earth and Planetary Science Letters, 237(3-4): 601-616. doi: 10.1016/j.epsl.2005.06.017 [9] Koppers, A.A.P., Watts, A.B., 2010. Intraplate seamounts as a window into deep earth processes. Oceanography, 23(1): 42-57. doi: 10.5670/oceanog.2010.61 [10] Li, C.F., Zhou, Z.Y., Li, J.B., et al., 2007. Structures of the northeasternmost South China Sea continental margin and ocean basin: geophysical constraints and tectonic implications. Mar. Geophys. Res. , 28(1): 59-79. doi: 10.1007/s11001-007-9014-9 [11] Li, C.F., Zhou, Z.Y., Li, J.B., et al., 2008. Magnetic zoning and seismic structure of the South China Sea Ocean basin. Mar. Geophys. Res. , 29: 223-238. doi: 10.1007/s11001-008-9059-4 [12] Li, J.B., Jin, X.L., Gao, J.Y., 2002. Tectonic topography of eastern sub-basin in later spreading. Science in China (Ser. D), 32(3): 239-248 (in Chinese). http://www.researchgate.net/publication/285323621_Tectonic_topography_of_eastern_sub-basin_in_later_spreading [13] Li, X.Y., Wu, Z.L., Xue, B., et al., 2007. Short-period auto-floating ocean bottom seismometer and its operational experiences. Journal of Tropical Oceanography, 26(5): 35-39 (in Chinese with English abstract). http://www.researchgate.net/publication/284038870_Short-period_auto-floating_ocean_bottom_seismometer_and_its_operational_experiences [14] Liu, J.H., 2000. The characteristics of seismic reflection waves in the middle area of the South China Sea and their significance. Acta Oceanologica Sinica, 22(6): 73-80 (in Chinese with English abstract). [15] Minshull, T.A., 2009. Geophysical characterisation of the ocean-continent transition at magma-poor rifted margins. C.R. Geoscience, 341(5): 382-393. doi: 10.1016/j.crte.2008.09.003 [16] Nissen, S.S., Hayes, D.E., Buhl, P., et al., 1995. Deep penetration seismic soudings across the northern margin of the South China Sea. J. Geophys. Res. , 100(B11): 22407-22433. doi: 10.1029/95JB01866 [17] Qiu, X.L., Zhou, D., Xia, K.Y., et al., 2000. OBH experiment and crustal structure of Xisha trough, South China Sea. Tropic Oceanology, 19(2): 9-18 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-RDHY200002001.htm [18] Qiu, X.L., Ye, S.Y., Wu, S.M., et al., 2001. Crustal structure across the Xisha trough, northwestern South China Sea. Tectonophysics, 341: 179-193. doi: 10.1016/S0040-1951(01)00222-0 [19] Qiu, X.L., Shi, X.B., Yan, P., et al., 2003. The deep seismic survey and research progress on crust structure of the northern South China Sea. Progress in Natural Science, 13(3): 231-236 (in Chinese). http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=zrkxjz-e200307001 [20] Qiu, X.L., Chen, Y., Zhu, R.X., et al., 2007. The application of large volume airgun sources to the onshore-offshore seismic surveys: implication of the experimental results in northern South China Sea. China Science Bulletin, 52(4): 553-560. doi: 10.1007/s11434-007-0051-1 [21] Ruan, A.G., Qiu, X.L., Li, J.B., et al., 2009. Wide aperture seismic sounding in the margin seas of China. South China Journal of Seismology, 29(2): 10-18 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-HNDI200902004.htm [22] Shi, X.B., Zhou, D., Zhang, Y.X., et al., 2002. Density, thermal and rheological strutures of Xisha trough, South China Sea. Journal of Tropical Oceanography, 21(2): 23-31 (in Chinese with English abstract). [23] Sun, Z., Zhong, Z.H., Zhou, D., et al., 2006. Research on opening mechanism of South China Sea: from anologue evidence. Science in China (Ser. D), 36(9): 797-810 (in Chinese). [24] Sun, Z., Zhong, Z.H., Keep, M., et al., 2009.3D analogue modeling of the South China Sea: a discussion on breakup pattern. Journal of Asian Earth Sciences, 34(4): 544-556. doi: 10.1016/j.jseaes.2008.09.002 [25] Wang, T.K., Chen, M.K., Lee, C.S., et al., 2006. Seismic imaging of the transitional crust across the northeastern margin of the South China Sea. Tectonophysics, 412(3-4): 237-254. doi: 10.1016/j.tecto.2005.10.039 [26] Watts, A.B., Cochran, J. R, Selzer, G., 1975. Gravity anomalies and flexure of the lithosphere : a three-dimensional study of the Great Meteor Seamount, Northeast Atlantic. J. Geophys. Res. , 80(11): 1391-4116. doi: 10.1029/JB080i011p01391 [27] Watts, A.B., ten Brink, U.S., Buhl, P., et al., 1985. A multichannel seismic study of lithospheric flexure across the Hawaiian-Emperor seamount chain. Nature, 315(9): 105-111. doi: 10.1038/315105a0 [28] Wei, X., Jia, C.Z., Zhu, Y.J., et al., 2010. Tectonic evolution and infilling characteristics of the aborted oceanic basin: taking Shuangfeng basin of South China Sea as an example. Acta Petrolei Sinica, 31(2): 173-179 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-SYXB201002002.htm [29] Wei, X.D., Zhao, M.H., Ruan, A.G., et al., 2010. Identification and application of shear waves along the profile OBS2006-3 in the mid-northern South China Sea. Journal of Tropical Oceanography, 29(5): 72-80 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-RDHY201005012.htm [30] Wu, S.M., Zhou, D., Qiu, X.L., 2001. Tectonic setting of the northern margin of South China Sea. Geological Journal of China Universities, 7(4): 419-426 (in Chinese with English abstract). [31] Wu, Z.L., Li, J.B., Ruan, A.G., et al., 2011. Crustal structure of the northwestern sub-basin, South China Sea: results from a wide angle seismic experiment. Science in China (Ser. D), 41(10): 1463-1476 (in Chinese). http://onlinelibrary.wiley.com/resolve/reference/XREF?id=10.1007/s11430-011-4324-9 [32] Xia, S.H., Zhao, M.H., Qiu, X.L., et al., 2010. Crustal structure in an onshore-offshore transitional zone near Hong Kong, northern South China Sea. Journal of Asian Earth Sciences, 37(40669): 460-472. doi: 10.1016/j.jseaes.2009.11.004 [33] Yan, P., Zhou, D., Liu, Z.S., 2001. A crustal structure profile across the northern continental margin of the South China Sea. Tectonophysics, 338(1): 1-21. doi: 10.1016/S0040-1951(01)00062-2 [34] Yao, B.C., 1996. Tectonic evolution of the South China Sea in Cenozoic. Marine Geology & Quaternary Geology, 16(2): 1-12 (in Chinese with English abstract). http://en.cnki.com.cn/article_en/cjfdtotal-hydz602.000.htm [35] Yao, B.C., 2002. Deformation characteristics of continental lithosphere when rifting and breaking-up. Marine Geology & Quaternary Geology, 22(3): 59-67 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-HYDZ200203010.htm [36] Zelt, C.A., Smith, R.B., 1992. Seismic traveltime inversion for 2-D crustal velocity structure. Geophys. J. Int. , 108(1): 16-34. doi: 10.1111/j.1365-246X.1992.tb00836.x [37] Zhao, M.H., Qiu, X.L., Xia, K.Y., et al., 2004. Onshore-offshore seismic data processing and preliminary results in NE South China Sea. Journal of Tropical Oceanography, 23(1): 58-63 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-RDHY200401008.htm [38] Zhao, M.H., Qiu, X.L., Xu, H.L., et al., 2006. Crustal structure and its low 2 velocity layer in transition zone of South China. Journal of Tropical Oceanography, 25(5): 36-42 (in Chinese with English abstract). http://www.researchgate.net/publication/306217964_Crustal_structure_and_its_low_2_velocity_layer_in_transition_zone_of_South_China [39] Zhao, M.H., Qiu, X.L., Xia, S.H., et al., 2010. Seismic structure in the northeastern South China Sea: S-wave velocity and Vp/Vs ratios derived from three-component OBS data. Tectonophysics, 480(40547): 183-197. doi: 10.1016/j.tecto.2009.10.004 [40] 敖威, 赵明辉, 丘学林, 等, 2010. 西南印度洋中脊三维地震探测中炮点与海底地震仪的位置校正. 地球物理学报, 53(12): 2982-2991. doi: 10.3969/j.issn.0001-5733.2010.12.022 [41] 丁巍伟, 黎明碧, 赵俐红, 等, 2009. 南海西北次海盆新生代构造-沉积特征及伸展模式探讨. 地学前缘, 16(4): 147-156. https://www.cnki.com.cn/Article/CJFDTOTAL-DXQY200904016.htm [42] 郝天珧, 刘建华, 宋海斌, 等, 2002. 华南及其相邻边缘海域一些重要断裂的地球物理证据. 地球物理学进展, 17(1): 13-23. https://www.cnki.com.cn/Article/CJFDTOTAL-DQWJ200201001.htm [43] 李家彪, 金翔龙, 高金耀, 2002. 南海东部海盆晚期扩张的构造地貌研究. 中国科学(D辑), 32(3): 239-248. https://www.cnki.com.cn/Article/CJFDTOTAL-JDXK200203008.htm [44] 李湘云, 吴振利, 薛彬, 等, 2007. SEDIS-IV型短周期自浮式海底地震仪及应用体会. 热带海洋学报26(5): 35-39. https://www.cnki.com.cn/Article/CJFDTOTAL-RDHY200705006.htm [45] 刘建华, 2000. 南海中部地震反射波特征及其地质解释. 海洋学报, 22(6): 73-80. https://www.cnki.com.cn/Article/CJFDTOTAL-SEAC200006008.htm [46] 丘学林, 周蒂, 夏戡原, 等, 2000. 南海西沙海槽地壳结构的海底地震仪探测与研究. 热带海洋, 19(2): 9-18. https://www.cnki.com.cn/Article/CJFDTOTAL-RDHY200002001.htm [47] 丘学林, 施小斌, 阎贫, 等, 2003. 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, 13(3): 231-236. https://www.cnki.com.cn/Article/CJFDTOTAL-ZKJZ200303001.htm [48] 阮爱国, 丘学林, 李家彪, 等, 2009. 中国海洋深地震探测与研究进展. 华南地震, 29(2): 10-18. https://www.cnki.com.cn/Article/CJFDTOTAL-HNDI200902004.htm [49] 施小斌, 周蒂, 张毅祥, 等, 2002. 南海西沙海槽岩石圈的密度结构与热-流变结构. 热带海洋学报, 21(2): 23-31. https://www.cnki.com.cn/Article/CJFDTOTAL-RDHY200202002.htm [50] 孙珍, 钟志洪, 周蒂, 等, 2006. 南海的发育机制研究: 相似模拟证据. 中国科学(D辑), 36(9): 797-810. https://www.cnki.com.cn/Article/CJFDTOTAL-JDXK200609001.htm [51] 魏喜, 贾承造, 祝永军, 等, 2010. 夭折大洋盆地构造演化及充填特征探讨——以南海双峰盆地为例. 石油学报, 31(2): 173-179. https://www.cnki.com.cn/Article/CJFDTOTAL-SYXB201002002.htm [52] 卫小冬, 赵明辉, 阮爱国, 等, 2010. 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, 29(5): 72-80. https://www.cnki.com.cn/Article/CJFDTOTAL-RDHY201005012.htm [53] 吴世敏, 周蒂, 丘学林, 2001. 南海北部陆缘的构造属性问题. 高校地质学报, 7(4): 419-426. https://www.cnki.com.cn/Article/CJFDTOTAL-GXDX200104005.htm [54] 吴振利, 李家彪, 阮爱国, 等, 2011. 南海西北次海盆地壳结构: 海底广角地震实验结果. 中国科学(D辑), 41(10): 1463-1476. https://www.cnki.com.cn/Article/CJFDTOTAL-JDXK201110009.htm [55] 姚伯初, 1996. 南海海盆新生代的构造演化史. 海洋地质与第四纪地质, 16(2): 1-12. https://www.cnki.com.cn/Article/CJFDTOTAL-HYDZ602.000.htm [56] 姚伯初, 2002. 大陆岩石圈在张裂和分离时的变形模式. 海洋地质与第四纪地质, 22(3): 59-67. https://www.cnki.com.cn/Article/CJFDTOTAL-HYDZ200203010.htm [57] 赵明辉, 丘学林, 夏戡原, 等, 2004. 南海东北部海陆联测地震数据处理及初步结果. 热带海洋学报, 23(1): 58-63. doi: 10.3969/j.issn.1009-5470.2004.01.008 [58] 赵明辉, 丘学林, 徐辉龙, 等, 2006. 华南海陆过渡带的地壳结构与壳内低速层. 热带海洋学报, 25(5): 36-42. https://www.cnki.com.cn/Article/CJFDTOTAL-RDHY200605006.htm -
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