中国境内天山地壳上地幔结构的地震层析成像
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摘要
根据横跨中国境内天山的库车—奎屯宽频带流动地震台阵和区域地震台网记录的近震和远震P波走时数据,利用地震层析成像方法重建了沿该地震台阵剖面下方400 km深度范围内地壳上地幔的P波速度结构.结果表明:沿新疆库车—奎屯剖面,天山地壳具有明显的横向分块结构,且南、北天山地壳显示了较为强烈的横向变形特征,表明塔里木地块对天山地壳具有强烈的侧向挤压作用;在塔里木和准噶尔地块上地幔顶部有厚度约60~90km的高速异常体,塔里木—南天山下方的高速异常体产生了较为明显的弯曲变形,而准噶尔—北天山下方的高速异常体向南一直俯冲到中天山南侧边界下方300 km的深度,两者形成了不对称对冲构造;在塔里木和准噶尔地块下方150~400 km深度存在上地幔低速体,其中塔里木地块一侧的上地幔低速物质上涌到南天山地块的下方;在塔里木—南天山200~300 km深度范围的上地幔存在高速异常体,它可能是地幔热物质向上迁移过程融断的塔里木岩石圈的拆离体.上述结果表明,塔里木地块的俯冲可能涉及整个岩石圈深度,但其前缘仅限于南天山的北缘;青藏高原隆升的远程效应可能不但驱动塔里木岩石圈向北俯冲,同时还造成天山造山带南侧上地幔物质的涌入;天山造山带上地幔广泛存在的低速异常有助于其上地幔的变形,而上地幔物质的强烈非均匀性应有助于推动天山造山带上地幔小尺度地幔对流的形成;根据研究区地壳上地幔速度结构特征推断,新近纪以来天山快速隆升的主要力源来自青藏高原快速隆升的远程效应,相对软弱的上地幔为加速天山造山带的变形和隆升创造了必要条件.
From the travel time data of the P-arrivals recorded by the passive seismic array across the Chinese Tianshan and the regional seismic network,the P wave velocity structure of the crust and upper mantle down to 400 km along Kuqa-Kuytun profile is reconstructed by using seismic tomography technique.Our results demonstrate that the crust along the profile has an obvious block structure and strong lateral crustal distortion.These manifest that the Tianshan crust is compressed strongly by the Tarim block.Beneath the Tarim and Junggar block,there are high-velocity anomalies with the thickness of 60～90 km at the top of the upper mantle.The high-velocity anomaly below the Tarim-South Tianshan has a clear curved distortion,and that below the Junggar-Northern Tianshan thrusts down to the depth of 300 km at the south side of the central Tianshan.Both of them construct an asymmetric bilateral thrusting system.Beneath the Tarim and Junggar block,in the depth range from 150 km to 400 km,exist low-velocity anomalies. One of them on the Tarim side rises to bellow the south Tianshan.In the upper mantle,at the depth of 200～300 km beneath the Tarim-South Tianshan,exists a high-velocity anomaly,which could be the detached lithosphere of the Tarim melted by the up-welling hot material of the upper mantle.All of our observations manifest that the lithosphere of Tarim block is involved in the northward subduction,but its front is limited to the north border of the south Tianshan.The long-range effect caused by the uplift of the Tibetan plateau could drive not only the subduction of the Tarim lithosphere,but also the upwelling of the upper mantle in the south side of the Tianshan orogenic belt.The low-velocity anomalies widely existed in the Tianshan upper mantle should facilitate the mantle deformation,and the large difference between the high and low velocity anomalies in the upper mantle may promote the small-scale mantle convection.According to the crustal and upper mantle velocity structure beneath the Tianshan orogenic belt,it could be inferred that the main source driving the quick uplift of the Tianshan since Miocene comes from the long-range effect caused by the uplift of the Tibetan plateau,and the relatively soft upper mantle beneath the Tianshan creates the necessary condition for accelerating the uplift and distortion of the crust.
From the travel time data of the P-arrivals recorded by the passive seismic array across the Chinese Tianshan and the regional seismic network,the P wave velocity structure of the crust and upper mantle down to 400 km along Kuqa-Kuytun profile is reconstructed by using seismic tomography technique.Our results demonstrate that the crust along the profile has an obvious block structure and strong lateral crustal distortion.These manifest that the Tianshan crust is compressed strongly by the Tarim block.Beneath the Tarim and Junggar block,there are high-velocity anomalies with the thickness of 60～90 km at the top of the upper mantle.The high-velocity anomaly below the Tarim-South Tianshan has a clear curved distortion,and that below the Junggar-Northern Tianshan thrusts down to the depth of 300 km at the south side of the central Tianshan.Both of them construct an asymmetric bilateral thrusting system.Beneath the Tarim and Junggar block,in the depth range from 150 km to 400 km,exist low-velocity anomalies. One of them on the Tarim side rises to bellow the south Tianshan.In the upper mantle,at the depth of 200～300 km beneath the Tarim-South Tianshan,exists a high-velocity anomaly,which could be the detached lithosphere of the Tarim melted by the up-welling hot material of the upper mantle.All of our observations manifest that the lithosphere of Tarim block is involved in the northward subduction,but its front is limited to the north border of the south Tianshan.The long-range effect caused by the uplift of the Tibetan plateau could drive not only the subduction of the Tarim lithosphere,but also the upwelling of the upper mantle in the south side of the Tianshan orogenic belt.The low-velocity anomalies widely existed in the Tianshan upper mantle should facilitate the mantle deformation,and the large difference between the high and low velocity anomalies in the upper mantle may promote the small-scale mantle convection.According to the crustal and upper mantle velocity structure beneath the Tianshan orogenic belt,it could be inferred that the main source driving the quick uplift of the Tianshan since Miocene comes from the long-range effect caused by the uplift of the Tibetan plateau,and the relatively soft upper mantle beneath the Tianshan creates the necessary condition for accelerating the uplift and distortion of the crust.
引文
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[13]胥颐,刘福田,刘建华等.中国西北大陆碰撞带的深部特征及其动力学意义.地球物理学报,2001,44(1):40~47Xu Y,Liu F T,Liu J H,et al.Deep features of continental collisionbelts in northwestern China and their dynamic implications.ChineseJ.Geophys.(in Chinese),2001,44(1):40~47
[14]Poupinet G,Avouac J P,Jiang M,et al.Intracontinental subductionand Palaeozoic inheritance of the lithosphere suggested by ateleseismic experiment across the Chinese Tien Shan.Terra Nova,2002,14(1):18~24
[15]Chen Y H,Roecker S W,Kasorev G L.Elevation of the 400kmdiscontinuity beneath the central Tien Shan:Case of missing root.Geophys.Res.Let.,1996,24(12):1531~1534
[16]Vinnik L P,Saipekova A M.Structure of the lithosphere andasthenosphere of the Tien Shan.Ann.Geophys.,1984,2(6):621~626
[17]Kosarev G L,Petersen N V,Vinnik L P,Roecker S W.Receiverfunctions for the Tien Shan analog broadband network:contrasts inthe evolution of structure across the Talasso_Fergano Fault.J.Geophys.Res.,1993,98(B3):4437~4448
[18]傅容珊,黄建华,徐耀民等.青藏高原—天山地区岩石层构造运动的地幔动力学机制.地球物理学报,1998,41(5):658~668Fu R S,Huang J H,Xu Y M,et al.Study of the mantle dynamics ofthe lithosphere movements in the region from Qinghai_Xizang plateauto Tianshan mountain.Chinese J.Geophys.(in Chinese),1998,41(5):658~668
[19]刘启元.关于天山陆内造山动力学问题.见:张中杰等主编.中国大陆地球深部结构与动力学研究.北京:科学出版社,2004.792~799Liu Q Y.On the dynamics of Tien Shan intracontinental orogenesis.In:Zhang Z J,et al.eds.The Earth Structure and Dynamics ofChinese Continent(in Chinese).Beijing:Science Press,2004.792~799
[20]李顺成,刘启元,陈九辉等.横跨天山的宽频带流动地震台阵观测.地球物理学进展,2005,20(4):955~960Li S C,Liu Q Y,Chen J H,et al.The experiment of passive seismicarray across the Chinese Tianshan.Progress in Geophysics(inChinese),2005,20(4):955~960
[21]李昱,刘启元,陈九辉等.中国境内天山地壳上地幔的S波速度结构.中国科学(D辑),已接收Li Y,Liu Q Y,Chen J H,et al.The S_wave velocity structure ofthe crust and upper mantle underneath the Chinese Tianshan.Sciencein China(Series D)(in Chinese),in press
[22]张培震,邓起东,张国民等.中国大陆的强震活动与活动地块.中国科学(D辑),2003,33(增):12~20Zhang P Z,Deng Q D,Zhang G M,et al.Active tectonic blocksand strong earthquakes in the continent of China.Science in China(Series D),2003,33(Suppl.):12~20
[23]Zhao D P,Hasegawa A,Horiuchi S.Tomographic imaging of P and Swave velocity structure beneath Northeastern Japan.J.Geophys.Res.,1992,97(B3):19909~19928
[24]Zhao D P,Hasegawa A,Kanamori H.Deep structure of Japansubduction zone as derived from local,regional,and teleseismicevents.J.Geophys.Res.,1994,99(B11):22313~22329.
[25]Kennett B L.IASPEI91 Seismological Tables.Research School ofEarth Sciences,Australian National University,Canberra,1991,167
[26]雷建设,周蕙兰.中国西南及邻区上地幔P波三维速度结构.地震学报,2002,24(2):126~134Lei J S,Zhou H L.3-D velocity structure of P wave in the uppermantle beneath south western China and its adjacent areas.ActaSeismologica Sinica(in Chinese),2002,24(2):126~134
[27]Lei J S,Zhao D P.P wave tomography and origin of the Changbaiintraplate volcano in Northeast Asia.Tectonophysics,2005,397:281~295
[28]杨主恩,张先康,赵瑞斌等.天山中段的深浅构造特征.地震地质,2005,27(1):11~19Yang Z E,Zhang X K,Zhao R B,et al.Characteristics of shallowand deep structures of the middle segment of the Tianshan mountains,China.Seismology and Geology,2005,27(1):11~19
[29]Chen C M,Lu H F,Dong J,et al.Closing history of the southernTianshan oceanic basin,western China:an oblique collisionalorogeny.Tectonophysics,1999,302:23~40
[2]彭树森.大地形变测量所反应的天山最新构造运动.内陆地震,1993,7(2):136~141Peng S S.On the new tectonic movement in Tianshan that reflectedby the geodesic deformation survey.Inland Earthquake(inChinese),1993,7(2):136~141
[3]王琪,丁国瑜,乔学军等.天山现今地壳快速缩短与南北地块的相对运动.科学通报,2000,45(14):1543~1547Wang Q,Ding G Y,Qiao X J,et al.Rapid crustal shortening andrelative motion of crustal blocks in the Tianshan.Science Bulletin,2000,45(14):1538~1542
[4]卢德源,李秋生,高锐等.横跨天山的人工爆炸地震剖面.科学通报,2000,45(9):982~988Lu D Y,Li Q S,Gao R,et al.A deep seismic sounding profileacross the Tianshan Mountains.Chinese Science Bulletin,2000,45(22):2100~2106
[5]高锐,肖序常,高弘等.西昆仑—塔里木—天山岩石圈深地震探测综述.地质通报,2002,21(1):11~18Gao R,Xiao X C,Gao H,et al.Summary of deep seismic probingof the lithospheric structure across the west Kunlun_Tarim_Tianshan.Geological Bulletin of China(in Chinese),2002,21(1):11~18
[6]Zhao J M,Liu G,Lu X,et al.Lithospheric structure and dynamicprocesses of the Tianshan orogenic belt and the Junggar basin.Tectonophysics,2003,376:199~239
[7]肖序常,刘训,高锐.新疆南部地壳结构和构造演化.北京:商务印书社,2004Xiao X C,Liu X,Gao R.The Crustal Structure and TectonicEvolution of Southern Xinjiang,China(in Chinese).Beijing:TheCommercial Press,2004
[8]Roecker S W,Sabitova T M,Vinnik L P,et al.Three_dimensionalelastic wave velocity structure of the western and central Tien Shan.J.Geophys.Res.,1993,98(B9):15779~15795
[9]胥颐,朱介寿,刘志坚等.新疆天山及邻区地壳上地幔三维速度图像.地震学报,1994,16(4):480~487Xu Y,Zhu J S,Liu Z J,et al.3_D image of crust and upper mantlein Xinjiang Tianshan.Acta seismologica Sinica(in Chinese),1994,16(4):480~487
[10]李强,刘瑞丰,杜安陆.新疆及其毗邻地区地震层析成像.地球物理学报,1994,37(3):311~320Li Q,Liu R F,Du A L.Seismic tomography of Xinjiang andadjacent region.Chinese J.Geophys.(in Chinese),1994,37(3):311~320
[11]魏素花,薛光琦,钱辉等.新疆库车—克拉玛依地震层析成像.地球物理学进展,2000,15(4):46~54Wei S H,Xue G Q,Qian H,et al.Xinjiang Kuche Kelamayiseismic tomography.Progress in Geophysics(in Chinese),2000,15(4):46~54
[12]胥颐,刘福田,刘建华等.中国西北大陆造山带及毗邻盆地的地震层析成像.中国科学(D辑),2000,30(2):113~122Xu Y,Liu F T,Liu J H,et al.Seismic tomography beneathnorthwestern orogenic belts and adjacent basins in Chinese continent.Science in China(Series D)(in Chinese),2000,30(2):113~122
[13]胥颐,刘福田,刘建华等.中国西北大陆碰撞带的深部特征及其动力学意义.地球物理学报,2001,44(1):40~47Xu Y,Liu F T,Liu J H,et al.Deep features of continental collisionbelts in northwestern China and their dynamic implications.ChineseJ.Geophys.(in Chinese),2001,44(1):40~47
[14]Poupinet G,Avouac J P,Jiang M,et al.Intracontinental subductionand Palaeozoic inheritance of the lithosphere suggested by ateleseismic experiment across the Chinese Tien Shan.Terra Nova,2002,14(1):18~24
[15]Chen Y H,Roecker S W,Kasorev G L.Elevation of the 400kmdiscontinuity beneath the central Tien Shan:Case of missing root.Geophys.Res.Let.,1996,24(12):1531~1534
[16]Vinnik L P,Saipekova A M.Structure of the lithosphere andasthenosphere of the Tien Shan.Ann.Geophys.,1984,2(6):621~626
[17]Kosarev G L,Petersen N V,Vinnik L P,Roecker S W.Receiverfunctions for the Tien Shan analog broadband network:contrasts inthe evolution of structure across the Talasso_Fergano Fault.J.Geophys.Res.,1993,98(B3):4437~4448
[18]傅容珊,黄建华,徐耀民等.青藏高原—天山地区岩石层构造运动的地幔动力学机制.地球物理学报,1998,41(5):658~668Fu R S,Huang J H,Xu Y M,et al.Study of the mantle dynamics ofthe lithosphere movements in the region from Qinghai_Xizang plateauto Tianshan mountain.Chinese J.Geophys.(in Chinese),1998,41(5):658~668
[19]刘启元.关于天山陆内造山动力学问题.见:张中杰等主编.中国大陆地球深部结构与动力学研究.北京:科学出版社,2004.792~799Liu Q Y.On the dynamics of Tien Shan intracontinental orogenesis.In:Zhang Z J,et al.eds.The Earth Structure and Dynamics ofChinese Continent(in Chinese).Beijing:Science Press,2004.792~799
[20]李顺成,刘启元,陈九辉等.横跨天山的宽频带流动地震台阵观测.地球物理学进展,2005,20(4):955~960Li S C,Liu Q Y,Chen J H,et al.The experiment of passive seismicarray across the Chinese Tianshan.Progress in Geophysics(inChinese),2005,20(4):955~960
[21]李昱,刘启元,陈九辉等.中国境内天山地壳上地幔的S波速度结构.中国科学(D辑),已接收Li Y,Liu Q Y,Chen J H,et al.The S_wave velocity structure ofthe crust and upper mantle underneath the Chinese Tianshan.Sciencein China(Series D)(in Chinese),in press
[22]张培震,邓起东,张国民等.中国大陆的强震活动与活动地块.中国科学(D辑),2003,33(增):12~20Zhang P Z,Deng Q D,Zhang G M,et al.Active tectonic blocksand strong earthquakes in the continent of China.Science in China(Series D),2003,33(Suppl.):12~20
[23]Zhao D P,Hasegawa A,Horiuchi S.Tomographic imaging of P and Swave velocity structure beneath Northeastern Japan.J.Geophys.Res.,1992,97(B3):19909~19928
[24]Zhao D P,Hasegawa A,Kanamori H.Deep structure of Japansubduction zone as derived from local,regional,and teleseismicevents.J.Geophys.Res.,1994,99(B11):22313~22329.
[25]Kennett B L.IASPEI91 Seismological Tables.Research School ofEarth Sciences,Australian National University,Canberra,1991,167
[26]雷建设,周蕙兰.中国西南及邻区上地幔P波三维速度结构.地震学报,2002,24(2):126~134Lei J S,Zhou H L.3-D velocity structure of P wave in the uppermantle beneath south western China and its adjacent areas.ActaSeismologica Sinica(in Chinese),2002,24(2):126~134
[27]Lei J S,Zhao D P.P wave tomography and origin of the Changbaiintraplate volcano in Northeast Asia.Tectonophysics,2005,397:281~295
[28]杨主恩,张先康,赵瑞斌等.天山中段的深浅构造特征.地震地质,2005,27(1):11~19Yang Z E,Zhang X K,Zhao R B,et al.Characteristics of shallowand deep structures of the middle segment of the Tianshan mountains,China.Seismology and Geology,2005,27(1):11~19
[29]Chen C M,Lu H F,Dong J,et al.Closing history of the southernTianshan oceanic basin,western China:an oblique collisionalorogeny.Tectonophysics,1999,302:23~40
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