南海北部洋陆转换带地震反射特征和结构单元划分
摘要
张裂大陆边缘和盆地主要通过岩石圈的伸展作用形成,被动大陆边缘岩石圈的减薄导致了岩浆的减压熔融,最终形成了洋壳和减薄的转换带。处理和分析了2010年中国科学院南海海洋研究所"实验2"号采集的南海北部地球物理调查的多道地震数据(MCS2010-1),总结了南海北部洋陆转换带的地震反射特征。转换带主要由北部裂陷期下沉区段,中部海山或埋藏海山隆起带和靠近海盆一侧的掀斜断块带组成。通过对比以前南海北部采集的反射地震数据和折射地震波速度模型,圈定了洋陆转换带的分布范围,洋陆转换带的宽度在南海东北部是225km,中部是160km,西北部是110km。依据零星的大于6级地震震中分布,揭示了南海北部洋陆转换带目前仍是一个地震构造活跃带。
Rifted continental margins and basins are mainly formed by the lithospheric extension.Thinned lithosphere of passive continental margins leads to decompression melt of magma and created oceanic crust as well as thinned ocean-continent transition zone.A multi-channel seismic Line MCS 2010-1 in the northern South China Sea,acquired by the R/V "Shiyan 2" of the South China Sea Institute of Oceanology in 2010,is processed and analyzed in this study.Reflection characteristics of a continent-ocean transition(COT) zone are summarized and outlined.Results show that the COT zone is mainly composed of the northern syn-rift subsidence zone,central volcanic or buried volcanic uplift zone,and tilt faulted blocks near the South China Sea basin.Compared to the previous seismic reflection data and refraction velocity models,the range of the COT zone is outlined,from about 225 km wide in the northeastern South China Sea,160 km wide in the central to 110 km in the northern-central South China Sea.Epicenter distributions of sporadic and larger than 6 magnitude earthquakes suggest that the COT zone in the northern South China Sea is still an active seismic zone.
Rifted continental margins and basins are mainly formed by the lithospheric extension.Thinned lithosphere of passive continental margins leads to decompression melt of magma and created oceanic crust as well as thinned ocean-continent transition zone.A multi-channel seismic Line MCS 2010-1 in the northern South China Sea,acquired by the R/V "Shiyan 2" of the South China Sea Institute of Oceanology in 2010,is processed and analyzed in this study.Reflection characteristics of a continent-ocean transition(COT) zone are summarized and outlined.Results show that the COT zone is mainly composed of the northern syn-rift subsidence zone,central volcanic or buried volcanic uplift zone,and tilt faulted blocks near the South China Sea basin.Compared to the previous seismic reflection data and refraction velocity models,the range of the COT zone is outlined,from about 225 km wide in the northeastern South China Sea,160 km wide in the central to 110 km in the northern-central South China Sea.Epicenter distributions of sporadic and larger than 6 magnitude earthquakes suggest that the COT zone in the northern South China Sea is still an active seismic zone.
引文
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[2]RANERO C,PéREZ-GUSSINYéM.Sequential faultingexplains the asymmetry and extension discrepancy ofconjugate margins[J].Nature,2010,468:294-300.
[3]ELDHOLM O,THIEDE J.ODP LEG SCIENTIFIC PARTY.Formation of the Norwegian Sea[J].Nature,1986,319:360-361.
[4]KORENAGA J,HOLBROOK W S,KENT G M,et al.,Crustal structure of the southeast Greenland margin fromjoint refraction and reflection seismic tomography[J].JGeophys Res,2000,105:21591–21614.
[5]MUTTER J C,TALWANI M,STOFFA P L.Evidence for athick oceanic crust off Norway[J].J Geophys Res,1984,89:483-502.
[6]MORGAN J V,BARTON P J,WHITE R S.The HattonBank continental margin-Ш.Structure from wide-angle OBSand multichannel seismic refraction profiles[J].Geophys JInt,1989,98:367-384.
[7]WHITMARSH R B,AVEDIK F,SAUNDERS M R.Theseismic structure of thinned continental crust in the northernBay of Biscay[J].Geophys J R Astr Soc,1986,86:589-602.
[8]WHITE R S,MCKENZIE D,O’NIONS R K.Oceaniccrustal thickness from seismic measurements and rare earthelement inversions[J].J Geophys Res,1992,97:19683–19715.
[9]REID I D.Crustal structure of a nonvolcanic rifted margineast of Newfoundland[J].J Geophys Res,1994,99(B8):15161-15180.
[10]KEEN C E,POTTER D P.Formation and evolution of theNova Scotian rifted margin:Evidence from deep seismicreflection data[J].Tectonics,1995,14(4):918–932.
[11]LAVIER L,MANATSCHAL G.A mechanism to thin thecontinental lithosphere at magmapoor margins[J].Nature,2006,440:324-328.
[12]YAN P,ZHOU D,LIU Z.A crustal structure profile acrossthe northern continental margin of the South China Sea[J].Tectonophysics,2001,338:1-21.
[13]WANG T,CHEN M,LEE C,et al.Seismic imaging of thetransitional crust across the northeastern margin of the SouthChina Sea[J].Tectonophysics,2006,412:237-254.
[14]QIU X,YE S,WU S,et al.Crustal structure across the XishaTrough,northwestern South China Sea[J].Tectonophysics,2001,341:179-193.
[15]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[J].自然科学进展,2003,13(3):231-236.
[16]丘学林,赵明辉,叶春明,等.南海东北部海陆联测与海底地震仪探测[J].大地构造与成矿学,2003,27(4):295-300.
[17]李家彪.中国边缘海形成演化与资源效应[M].北京:海洋出版社,2008:1-509.
[18]MINSHULL T A.Geophysical characterisation of theocean–continent transition at magma-poor rifted margins[J].C R Geoscience,2009,341:382-393.
[19]TAYLOR B,HAYES D E.Origin and history of the SouthChina Basin[M]//HAYES D E.Tectonic and geologicevolution of southeast Asian seas and islands,GeophysMonogr Ser.Washington D C:AGU,1983,27:23-56.
[20]BOWIN C,LU R S,LEE C S,SCHOUTEN H.Plateconvergence and accretion in Taiwan-Luzon region[J].TheAmerican Association of Petroleum Geologists Bulletin,1978,62:1645-1672.
[21]TAYLOR B,HAYES D E.The tectonic evolution of theSouth China Sea Basin[M]//HAYES D E.Tectonic andgeologic evolution of southeast Asian seas and islands,Geophys Monogr Ser.Washington D C:AGU,1980,23:89-104.
[22]BRIAIS A,PATRIAT P,TAPPONNIER P.Updatedinterpretation of magnetic anomalies and seafloor spreadingstages in the South China Sea:Implications for the Tertiarytectonics of Southeast Asia[J].J Geophys Res,1993,98(B4):6299–6328.
[23]BARCKHAUSEN U,ROESER H A.Seafloor spreadinganomalies in South China Sea revisited[M]//CLIFT P,KUHNT W,WANG P,et al.Continent-ocean interactionswithin East Asian marginal seas,Geophys Monogr Ser.Washington D C:AGU,2004,149:121-125.
[24]姚伯初.南海北部陆缘新生代构造运动初探[J].南海地质研究,1993,5:1-12.
[25]夏戡原,黄慈流,黄志明.南海东北部台湾西南海区深部地壳结构特征[C]∥陈运泰,滕吉文,阚荣举,等.中国大陆地震学与地球内部物理学研究进展——庆贺曾融生院士八十寿辰.北京:地震出版社,2004:135-145.
[26]龚再升,李思田,谢泰俊,等.南海北部大陆边缘盆地分析与油气聚集[M].北京:科学出版社,1997:1-510.
[27]朱俊江,丘学林,詹文欢,等.南海东北部海沟的震源机制解及其构造意义[J].地震学报,2005,27(3):260-268.
[28]孙金龙,夏少红,徐辉龙,等.2010年南海北部海陆联测项目简介及初步成果[J].华南地震,2010,30(6):45-52.
[29]刘建华,南海中部地震反射波特征及其地质解释[J].海洋学报,2000,22:73-80.
[30]金庆焕.南海地质与油气资源[M].北京:地质出版社,1989:41-310.
[31]ZHAO MINGHUI,QIU XUELIN,XIA SHAOHONG,etal.Seismic structure in the northeastern South China Sea:S-wave velocity and Vp/Vs rations derived fromthree-component OBS data[J].Tectonophysics,2010,480:183-197.
[32]LI C,ZHOU Z,LI J,et al.,Magnetic zoning and seismicstructure of the South China Sea ocean basin[J].MarineGeophysical Researches,2008,29:223-238.
[33]HAYES D E,NISSEN S,BUHL P,et al.Throughgoingcrustal faults along the northern margin of the South ChinaSea and their role in crustal extension[J].J Geophys Res,1995,100(B11):22435-22446.
[34]LüDMANN T,WONG H K.Neotectonic regime on thepassive continental margin of the northern South ChinaSea[J].Tectonophysics,1999,311:113-138.
[35]张健,汪集旸.南海北部大陆边缘深部地热特征[J].科学通报,2000,45:1095-1100.
[36]施小斌,丘学林,夏戡原,等.南海热流特征及其构造意义[J].热带海洋学报,2003,22:63-73.
[37]SHI X,QIU X,XIA K,et al.Characteristics of surface heatflow in the South China Sea[J].Journal of Asian EarthSciences,22:265-277.
[38]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[J].地球物理学报,2011,54:3325-3335.
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