南海西沙石岛地震台下的地壳结构研究
摘要
为加强海上天然地震观测和岩石圈结构研究,我们在南海西沙群岛建立了石岛流动地震台,进行了为期一年多的观测试验.观测结果表明,虽然岛礁区的地震数据受热带气旋影响期间背景噪声较大,但仍能记录到MW6级以上的地震.本文对具有清晰P波波形的远震记录进行了接收函数处理和计算模拟,得到台站下简单的地壳结构模型,其莫霍面深度为28 km,上地壳顶部有一层2 km厚的低速层,横波速度只有2.3 km/s,向下逐渐过渡到横波速度为3.8 km/s的下地壳.与已有的研究结果比较,发现石岛台与琼中台的地壳结构模型是西沙海槽剖面的自然延伸,西沙地块的地壳结构属减薄型陆壳,可与华南地块的正常陆壳对比.
We installed a temporary earthquake station at Shidao on Xisha Islands of South China Sea to study the seismicity and lithospheric structure of the region,and carried out the observation experiment for more than one year.Although the seismic data in reef and island areas have relatively large background noise,especially during the passage of a tropical cyclone,earthquakes above M-W 6 can still be recorded.In this paper,those teleseismic records with clear P waveforms are chosen to carry out receiver function analysis and modeling.A simple crustal structure model beneath the station is obtained,in which the Moho depth is 28 km.On the top of the upper crust is a 2 km-thick low velocity layer with a shear wave velocity of only 2.3 km/s.The shear wave velocity increases gradually with depth to 3.8 km/s in the lower crust.We compared this model with previous results and discovered that the models of Shidao Station and Qiongzhong Station(QIZ) are the natural extensions of the Xisha Trough section.The crustal structure of Xisha Block consists of thinned continental crust,with a velocity structure that is similar to the normal continental crust of South China Block.
We installed a temporary earthquake station at Shidao on Xisha Islands of South China Sea to study the seismicity and lithospheric structure of the region,and carried out the observation experiment for more than one year.Although the seismic data in reef and island areas have relatively large background noise,especially during the passage of a tropical cyclone,earthquakes above M-W 6 can still be recorded.In this paper,those teleseismic records with clear P waveforms are chosen to carry out receiver function analysis and modeling.A simple crustal structure model beneath the station is obtained,in which the Moho depth is 28 km.On the top of the upper crust is a 2 km-thick low velocity layer with a shear wave velocity of only 2.3 km/s.The shear wave velocity increases gradually with depth to 3.8 km/s in the lower crust.We compared this model with previous results and discovered that the models of Shidao Station and Qiongzhong Station(QIZ) are the natural extensions of the Xisha Trough section.The crustal structure of Xisha Block consists of thinned continental crust,with a velocity structure that is similar to the normal continental crust of South China Block.
引文
[1]Yan P,Zhou D,Liu Z S.A crustal structure profile across thenorthern continental margin of the South China Sea.Tectonophysics,2001,338:1~21
[2]夏戡原,周蒂,苏达权等.莺歌海盆地速度结构及其对油气勘探的意义.科学通报,1998,43(4):361~367Xia K Y,Zhou D,Su D Q,et al.The velocity structure of theYinggehai Basin and its hydrocarbon implication.Chinese ScienceBulletin(in Chinese),1998,43(4):361~367
[3]丘学林,周蒂,夏戡原等.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,2000,19(2):10~19Qiu X L,Zhou D,Xia K Y,et al.OBH experiment and crustalstructure of Xisha Trough,South China Sea.Tropic Oceanology(inChinese),2000,19(2):10~19
[4]Qiu X,Ye S,Wu S,et al.Crustal structure across the XishaTrough,northwestern South China Sea.Tectonophysics,2001,341:179~193
[5]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.大地构造与成矿,2003,27(4):295~281Qiu X L,Zhao M H,Ye C M,et al.Ocean bottom seismometer andonshore-offshore seismic experiment in northeastern South China Sea.Geotectonica et Metallogenia(in Chinese),2003,27(4):295~281
[6]赵明辉,丘学林,叶春明等.南海东北部海陆联测与滨海断裂带两侧地壳结构分析.地球物理学报,2004,47(5):845~852Zhao M H,Qiu X L,Ye C M,et al.Analysis on deep crustalstructure along the onshore-offshore seismic profile across the Binhai(Littoral)Fault Zone in northeastern South China Sea.Chinese J.Geophys.(in Chinese),2004,47(5):845~852
[7]Wang T K,Chen M K,Lee C S,et al.Seismic imaging of thetransitional crust across the northeastern margin of the South ChinaSea.Tectonophysics,2006,412(3/4):237~254
[8]吴世敏,周蒂,丘学林.南海北部陆缘的构造属性问题.高校地质学报,2001,7(4):419~426Wu S M,Zhou D,Qiu X L.Tectonic setting of the northern marginof South China Sea.Geological Journal of China Universities(inChinese),2001,7(4):419~426
[9]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):231~236Qiu X L,Shi X B,Yan P,et al.Recent progress of deep seismicexperiments and studies of crustal structure in northern South ChinaSea.Progress in Natural Science(in Chinese),2003,13(3):231~236
[10]Hayes D E,Nissen S S.The South China Sea margins:Implicationsfor rifting contrasts.Earth and Planetary Science Letters,2005,237:601~616
[11]丘学林,陈,朱日祥等.大容量气枪震源在海陆联测中的应用:南海北部试验结果分析.科学通报,出版中Qiu X L,Chen Y,Zhu R X,et al.The application of large volumeairgun sources to the onshore-offshore seismic surveys:Implicationfrom the experimental results in northern South China Sea.ChineseScience Bulletin(in Chinese),in Press
[12]刘建华,吴华,刘福田.华南及其海域三维速度分布特征与岩石层结构.地球物理学报,1996,39(4):483~492Liu J H,Wu H,Liu F T.3D velocity distribution and lithosphericstructure in South China and its contiguous sea area.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1996,39(4):483~492
[13]胥颐,刘建华,刘福田等.哀牢山-红河断裂带及其邻区的地壳上地幔结构.中国科学,2003,33(12):1201~1208Xu Y,Liu J H,Liu F T,et al.Crust and upper mantle structure ofthe Ailao Shan-Red River fault zone and adjacent regions.Science inChina(Series D)(in Chinese),2003,33(12):1201~1208
[14]郑月军,黄忠贤,刘福田等.中国东部海域地壳—上地幔瑞利波速度结构研究.地球物理学报,2000,43(4):480~487Zheng Y J,Huang Z X,Liu F T,et al.Rayleigh wave velocity andstructure of the crust and upper mantle beneath the seas in easternChina.Chinese J.Geophys.(in Chinese),2000,43(4):480~487
[15]朱介寿,曹家敏,蔡学林等.东亚及西太平洋边缘海高分辨率面波层析成像.地球物理学报,2002,45(5):646~664Zhu J S,Cao J M,Cai X L,et al.High resolution surface wavetomography in East Asia and West Pacific marginal seas.Chinese J.Geophys.(in Chinese),2002,45(5):646~664
[16]Langston C A.Structure under Mount Rainier,Washington,inferredfrom teleseismic body waves.J.Geophys.Res.,1979,84:4749~4762
[17]Owens T J,Zandt G,Taylor S R.Seismic evidence for an ancient riftbeneath the Cumberland Plateau,Tennessee:A detailed analysis ofbroadband teleseismic P waveforms.J.Geophys.Res.,1984,89:7783~7795
[18]Ammon C J,Randall G E,Zandt G.On the non-uniqueness ofreceiver function inversions.J.Geophys.Res.,1990,95:15303~15318
[19]赵焕庭,宋朝景,余克服等.西沙群岛永兴岛和石岛的自然与开发.海洋通报,1994,13(5):44~56Zhao H T,Song C J,Yu K F,et al.Nature and development ofYongxing Island and Shi Island of Xisha Islands.Marine ScienceBulletin(in Chinese),1994,13(5):44~56
[20]胥颐,刘建华,傅竹武等.西沙群岛和哀牢山-红河地区的宽频带地震观测.热带海洋学报,2003,22(2):83~88Xu Y,Liu J H,Fu Z W,et al.Broadband earthquake observation inXisha Islands and Ailao Shan-Red River Region.Journal ofTropicalOceanography(in Chinese),2003,22(2):83~88
[21]Buland R,Chapman C H.The computation of seismic travel times.BSSA,1983,73:1271~1302
[22]香港天文台.二零一热带气旋.2002,143Hong Kong Observatory.Tropical cyclones in 2001.2002,143
[23]香港天文台.二零二热带气旋.2003,107Hong Kong Observatory.Tropical cyclones in 2002.2003,107
[24]陈子通.“黄蜂”登陆过程中路径变化的可能成因分析.热带气象学报,2004,20(6):625~632Chen Z T.A possible reason of track variation of Vongfong duringlanding.Journal of Tropical Meteorology(in Chinese),2004,20(6):1~21
[25]Priestley K,Zandt G,Randall G.Crustal structure in easternKazakh,U.S.S.R.from teleseismic receiver functions.Geophys.Res.Lett.,1988,15:613~616
[26]Qiu X,Priestley K,McKenzie D.Average lithospheric structure ofsouthern Africa.Geophys.J.Int.,1996,127(4):563~587
[27]刘启元,Kind R,李顺成.中国数字地震台网的接收函数及其非线性反演.地球物理学报,1997,40(3):356~368Liu Q Y,Kind R,Li S C.The receiver functions at the stations ofthe Chinese Digital Seismic Network(CDSN)and their nonlinearinversion.Chinese J.Geophys.(Acta Geophysica Sinica)(inChinese),1997,40(3):356~368
[28]吴庆举,曾融生.用宽频带远震接收函数研究青藏高原的地壳结构.地球物理学报,1998,41(5):669~679Wu Q J,Zeng R S.The crustal structure of Qinghai-Xizang Plateauinferred from broadband teleseismic waveform.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1998,41(5):669~679
[29]Mangino S,Priestley K,Ebel J.The receiver structure beneath theChina Digital Seismograph Network stations.Bull.Seismol.Soc.Am.,1999,89(4):1053~1076
[30]Kennett B L N.Seismic Wave Propagation in Stratified Media.Cambridge University Press,Cambridge,1983.342
[31]Owens T J,Crosson R S.Shallow structure effects on broadbandteleseismic P waveforms.Bull.Seismol.Soc.Am.,1988,78:96~108
[32]Mangino S,Priestley K.The crustal structure of the southern Caspianregion.Geophys.J.Int.,1998,133(3):630~648
[33]Randalll G.Efficient calculation of differential seismograms forlithospheric receiver functions.Geophys.J.Int.,1989,99:469~481
[34]Qiu X,Priestley K,McKenzie D.Teleseismic P-waveform receiverfunction analysis and its application to Qiongzhong station(QIZ)ofHainan Island,NW South China Sea.Journal of Geosciences ofChina,2002,4(1):1~8
[35]Shi X,Zhou D,Qiu X,et al.Thermal and rheological structure ofthe Xisha Trough,South China Sea.Tectonophysics,2002,351:285~300
[36]孙志国,韩昌甫,鞠连军等.青藏高原隆升与西沙珊瑚礁沉积的对比.海洋科学,1997,(4):64~67Sun Z G,Han C F,Ju L J,et al.Comparison between the uplift ofthe Tibetan Plateau and the sedimentation of coral reefs in XishaIslands.Marine Sciences(in Chinese),1997,(4):64~67
[37]刘健,韩春瑞,吴建政等.西沙更新世礁灰岩大气淡水成岩的地球化学证据.沉积学报,1998,16(4):71~77Liu J,Han C R,Wu J Z,et al.Geochemical evidence for themeteoric diagenesis in Pleistocene reef limestones of Xisha Islands.Acta Sedimentologica Sinica(in Chinese),1998,16(4):71~77
[38]孙嘉谋.西沙基底形成时代的商榷.海洋地质与第四纪地质,1987,7(4):5~6Sun J M.A discussion on the formation ages of the bedrock in theXisha Islands.Marine Geology&Quaternary Geology(in Chinese),1987,7(4):5~6
[39]阮爱国,李家彪,郝天珧等.石岛地震台远震记录反演研究.海洋学报,2006,20(2):85~92Ruan A G,Li J B,Hao T Y,et al.Inversion of far-field seismicwaves at Shidao Seismographic Station.Acta Oceanologica Sinica(inChinese),2006,20(2):85~92
[2]夏戡原,周蒂,苏达权等.莺歌海盆地速度结构及其对油气勘探的意义.科学通报,1998,43(4):361~367Xia K Y,Zhou D,Su D Q,et al.The velocity structure of theYinggehai Basin and its hydrocarbon implication.Chinese ScienceBulletin(in Chinese),1998,43(4):361~367
[3]丘学林,周蒂,夏戡原等.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,2000,19(2):10~19Qiu X L,Zhou D,Xia K Y,et al.OBH experiment and crustalstructure of Xisha Trough,South China Sea.Tropic Oceanology(inChinese),2000,19(2):10~19
[4]Qiu X,Ye S,Wu S,et al.Crustal structure across the XishaTrough,northwestern South China Sea.Tectonophysics,2001,341:179~193
[5]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.大地构造与成矿,2003,27(4):295~281Qiu X L,Zhao M H,Ye C M,et al.Ocean bottom seismometer andonshore-offshore seismic experiment in northeastern South China Sea.Geotectonica et Metallogenia(in Chinese),2003,27(4):295~281
[6]赵明辉,丘学林,叶春明等.南海东北部海陆联测与滨海断裂带两侧地壳结构分析.地球物理学报,2004,47(5):845~852Zhao M H,Qiu X L,Ye C M,et al.Analysis on deep crustalstructure along the onshore-offshore seismic profile across the Binhai(Littoral)Fault Zone in northeastern South China Sea.Chinese J.Geophys.(in Chinese),2004,47(5):845~852
[7]Wang T K,Chen M K,Lee C S,et al.Seismic imaging of thetransitional crust across the northeastern margin of the South ChinaSea.Tectonophysics,2006,412(3/4):237~254
[8]吴世敏,周蒂,丘学林.南海北部陆缘的构造属性问题.高校地质学报,2001,7(4):419~426Wu S M,Zhou D,Qiu X L.Tectonic setting of the northern marginof South China Sea.Geological Journal of China Universities(inChinese),2001,7(4):419~426
[9]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):231~236Qiu X L,Shi X B,Yan P,et al.Recent progress of deep seismicexperiments and studies of crustal structure in northern South ChinaSea.Progress in Natural Science(in Chinese),2003,13(3):231~236
[10]Hayes D E,Nissen S S.The South China Sea margins:Implicationsfor rifting contrasts.Earth and Planetary Science Letters,2005,237:601~616
[11]丘学林,陈,朱日祥等.大容量气枪震源在海陆联测中的应用:南海北部试验结果分析.科学通报,出版中Qiu X L,Chen Y,Zhu R X,et al.The application of large volumeairgun sources to the onshore-offshore seismic surveys:Implicationfrom the experimental results in northern South China Sea.ChineseScience Bulletin(in Chinese),in Press
[12]刘建华,吴华,刘福田.华南及其海域三维速度分布特征与岩石层结构.地球物理学报,1996,39(4):483~492Liu J H,Wu H,Liu F T.3D velocity distribution and lithosphericstructure in South China and its contiguous sea area.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1996,39(4):483~492
[13]胥颐,刘建华,刘福田等.哀牢山-红河断裂带及其邻区的地壳上地幔结构.中国科学,2003,33(12):1201~1208Xu Y,Liu J H,Liu F T,et al.Crust and upper mantle structure ofthe Ailao Shan-Red River fault zone and adjacent regions.Science inChina(Series D)(in Chinese),2003,33(12):1201~1208
[14]郑月军,黄忠贤,刘福田等.中国东部海域地壳—上地幔瑞利波速度结构研究.地球物理学报,2000,43(4):480~487Zheng Y J,Huang Z X,Liu F T,et al.Rayleigh wave velocity andstructure of the crust and upper mantle beneath the seas in easternChina.Chinese J.Geophys.(in Chinese),2000,43(4):480~487
[15]朱介寿,曹家敏,蔡学林等.东亚及西太平洋边缘海高分辨率面波层析成像.地球物理学报,2002,45(5):646~664Zhu J S,Cao J M,Cai X L,et al.High resolution surface wavetomography in East Asia and West Pacific marginal seas.Chinese J.Geophys.(in Chinese),2002,45(5):646~664
[16]Langston C A.Structure under Mount Rainier,Washington,inferredfrom teleseismic body waves.J.Geophys.Res.,1979,84:4749~4762
[17]Owens T J,Zandt G,Taylor S R.Seismic evidence for an ancient riftbeneath the Cumberland Plateau,Tennessee:A detailed analysis ofbroadband teleseismic P waveforms.J.Geophys.Res.,1984,89:7783~7795
[18]Ammon C J,Randall G E,Zandt G.On the non-uniqueness ofreceiver function inversions.J.Geophys.Res.,1990,95:15303~15318
[19]赵焕庭,宋朝景,余克服等.西沙群岛永兴岛和石岛的自然与开发.海洋通报,1994,13(5):44~56Zhao H T,Song C J,Yu K F,et al.Nature and development ofYongxing Island and Shi Island of Xisha Islands.Marine ScienceBulletin(in Chinese),1994,13(5):44~56
[20]胥颐,刘建华,傅竹武等.西沙群岛和哀牢山-红河地区的宽频带地震观测.热带海洋学报,2003,22(2):83~88Xu Y,Liu J H,Fu Z W,et al.Broadband earthquake observation inXisha Islands and Ailao Shan-Red River Region.Journal ofTropicalOceanography(in Chinese),2003,22(2):83~88
[21]Buland R,Chapman C H.The computation of seismic travel times.BSSA,1983,73:1271~1302
[22]香港天文台.二零一热带气旋.2002,143Hong Kong Observatory.Tropical cyclones in 2001.2002,143
[23]香港天文台.二零二热带气旋.2003,107Hong Kong Observatory.Tropical cyclones in 2002.2003,107
[24]陈子通.“黄蜂”登陆过程中路径变化的可能成因分析.热带气象学报,2004,20(6):625~632Chen Z T.A possible reason of track variation of Vongfong duringlanding.Journal of Tropical Meteorology(in Chinese),2004,20(6):1~21
[25]Priestley K,Zandt G,Randall G.Crustal structure in easternKazakh,U.S.S.R.from teleseismic receiver functions.Geophys.Res.Lett.,1988,15:613~616
[26]Qiu X,Priestley K,McKenzie D.Average lithospheric structure ofsouthern Africa.Geophys.J.Int.,1996,127(4):563~587
[27]刘启元,Kind R,李顺成.中国数字地震台网的接收函数及其非线性反演.地球物理学报,1997,40(3):356~368Liu Q Y,Kind R,Li S C.The receiver functions at the stations ofthe Chinese Digital Seismic Network(CDSN)and their nonlinearinversion.Chinese J.Geophys.(Acta Geophysica Sinica)(inChinese),1997,40(3):356~368
[28]吴庆举,曾融生.用宽频带远震接收函数研究青藏高原的地壳结构.地球物理学报,1998,41(5):669~679Wu Q J,Zeng R S.The crustal structure of Qinghai-Xizang Plateauinferred from broadband teleseismic waveform.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1998,41(5):669~679
[29]Mangino S,Priestley K,Ebel J.The receiver structure beneath theChina Digital Seismograph Network stations.Bull.Seismol.Soc.Am.,1999,89(4):1053~1076
[30]Kennett B L N.Seismic Wave Propagation in Stratified Media.Cambridge University Press,Cambridge,1983.342
[31]Owens T J,Crosson R S.Shallow structure effects on broadbandteleseismic P waveforms.Bull.Seismol.Soc.Am.,1988,78:96~108
[32]Mangino S,Priestley K.The crustal structure of the southern Caspianregion.Geophys.J.Int.,1998,133(3):630~648
[33]Randalll G.Efficient calculation of differential seismograms forlithospheric receiver functions.Geophys.J.Int.,1989,99:469~481
[34]Qiu X,Priestley K,McKenzie D.Teleseismic P-waveform receiverfunction analysis and its application to Qiongzhong station(QIZ)ofHainan Island,NW South China Sea.Journal of Geosciences ofChina,2002,4(1):1~8
[35]Shi X,Zhou D,Qiu X,et al.Thermal and rheological structure ofthe Xisha Trough,South China Sea.Tectonophysics,2002,351:285~300
[36]孙志国,韩昌甫,鞠连军等.青藏高原隆升与西沙珊瑚礁沉积的对比.海洋科学,1997,(4):64~67Sun Z G,Han C F,Ju L J,et al.Comparison between the uplift ofthe Tibetan Plateau and the sedimentation of coral reefs in XishaIslands.Marine Sciences(in Chinese),1997,(4):64~67
[37]刘健,韩春瑞,吴建政等.西沙更新世礁灰岩大气淡水成岩的地球化学证据.沉积学报,1998,16(4):71~77Liu J,Han C R,Wu J Z,et al.Geochemical evidence for themeteoric diagenesis in Pleistocene reef limestones of Xisha Islands.Acta Sedimentologica Sinica(in Chinese),1998,16(4):71~77
[38]孙嘉谋.西沙基底形成时代的商榷.海洋地质与第四纪地质,1987,7(4):5~6Sun J M.A discussion on the formation ages of the bedrock in theXisha Islands.Marine Geology&Quaternary Geology(in Chinese),1987,7(4):5~6
[39]阮爱国,李家彪,郝天珧等.石岛地震台远震记录反演研究.海洋学报,2006,20(2):85~92Ruan A G,Li J B,Hao T Y,et al.Inversion of far-field seismicwaves at Shidao Seismographic Station.Acta Oceanologica Sinica(inChinese),2006,20(2):85~92
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