利用接收函数研究青藏高原东南缘的地壳上地幔结构
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摘要
本文使用位于青藏高原东南缘的25个地震台站的远震数据,采用P波和S波接收函数的方法研究了台站下方的Moho深度、泊松比以及地幔过渡带的厚度.计算结果表明:①青藏高原东南缘的地壳厚度由松潘—甘孜地体和羌塘地体的约60km,向邻区的印支地体以及扬子板块分别减薄为约38km和约42km;②羌塘地体的泊松比主要集中范围为0.25～0.28,地壳物质组分主要为中基性岩石,推测与下地壳镁铁质成分的增加有关.松潘—甘孜块体、印支块体和扬子板块的泊松比为0.25～0.26,主要为中酸性岩石组分.缺乏高的泊松比(≥0.30)分布表明青藏高原东南缘的地壳不存在广泛的部分熔融,但是不排除局部部分熔融的存在;③青藏高原东南缘的羌塘地体内存在一个比较明显的、异常变化范围为10～26km的地幔过渡带增厚区域,其对应着地幔过渡带内100℃～260℃的温度降低,可以推断与此异常区域的地幔过渡带内存在俯冲的板块有关.
Combined P and S receiver functions from seismograms of teleseismic events recorded at 25 temporary broadband seismic stations in the southeastern Tibetan Plateau are used to map the Moho depth,Poisson's ratio and the thickness of the mantle transition zone.The main results are as follows:①The crustal thickness gradually decrease from～60 km in Songpan-Ganze terrane and Qiangtang Terrane to～38 km in Indochina block and～42 km in Yangtze block.② The Poisson s ratios in Qiangtang terrane mainly range from 0.25 to 0.28,which indicate that the crust is mainly composed of intermediate and mafic rocks and may be caused by the increased mafic rocks in lower crust.But the Poisson's ratios range from 0.25 to 0.26 in Songpan-Ganze terrane,Indochina block and Yangtze block,which indicate that the crust is predominantly felsic and intermediate rocks.The lack of consistent high Poisson's ratio (≥0.30) shows that widespread partial melt does not exist within the curst,but does not exclude the presence of local partial melt.③There is an obvious thickened zone of the mantle transition zone compared with IASP91 standard value which varies from 10 km to 26 km in Qiangtang terrane.The anomaly suggests that the temperature is about 100℃ to 260℃ lower than global average value within the mantle transition zone,and it may be attributed to the presence of a subducted slab within the mantle transition zone.
Combined P and S receiver functions from seismograms of teleseismic events recorded at 25 temporary broadband seismic stations in the southeastern Tibetan Plateau are used to map the Moho depth,Poisson's ratio and the thickness of the mantle transition zone.The main results are as follows:①The crustal thickness gradually decrease from～60 km in Songpan-Ganze terrane and Qiangtang Terrane to～38 km in Indochina block and～42 km in Yangtze block.② The Poisson s ratios in Qiangtang terrane mainly range from 0.25 to 0.28,which indicate that the crust is mainly composed of intermediate and mafic rocks and may be caused by the increased mafic rocks in lower crust.But the Poisson's ratios range from 0.25 to 0.26 in Songpan-Ganze terrane,Indochina block and Yangtze block,which indicate that the crust is predominantly felsic and intermediate rocks.The lack of consistent high Poisson's ratio (≥0.30) shows that widespread partial melt does not exist within the curst,but does not exclude the presence of local partial melt.③There is an obvious thickened zone of the mantle transition zone compared with IASP91 standard value which varies from 10 km to 26 km in Qiangtang terrane.The anomaly suggests that the temperature is about 100℃ to 260℃ lower than global average value within the mantle transition zone,and it may be attributed to the presence of a subducted slab within the mantle transition zone.
引文
[1] Royden L J,Burchfiel B C,van der Hilst R D.The geological evolution of the Tibetan Plateau.Science,2008,321:1054-1058
[2] Xu L,Rondenay S,van der Hilst R D.Strucure of the crust beneath the southeastern Tibetan Plateau from teleseismic receiver functions.Physics of the Earth and Planetary Interiors,2007,165:176-193
[3] 滕吉文,白登海,杨辉等.2008汶川Ms8． 0地震发生的深层过程和动力学响应.地球物理学报,2008,51(5) :1385-1402 Yao H.van der Hilst R D,De Hoop M V.Surface-wave array tomography in SE Tibet from ambient seismic noise and two-station analysis:Ⅰ-Phase velocity maps.Geophys.J.Int.,2006,166:732-744
[5] 楼海,王椿镛,吕智勇等.2008年汶川Ms8． 0级地震的深部构造环境--远震P波接收函数和布格重力异常的联合解释.中国科学(D辑:地球科学),2008,38(10) :1207-1220 Lou H,Wang C Y,Lü Z Y,et al.Deep tectonic environment of the Wenchuan M_s 8． 0 earthquake of 2008． -Joint interpretation of P receiver functions and Bouguer gravity anomalies.Science in China (Series D-Earth Sciences),2008,38(10) :1207-1220
[6] Wang C Y,Lou H,Lü Z,et al.S-wave crustal and upper mantle's velocity structure in the eastern Tibetan Plateau-Deep environment of lower crustal flow.Science in China (Series D-Earth Sciences),2008,51 (2) :263-274
[7] Zurek B D,Meltzer A,Sol S,et al.Measurements of crustal thickness and Poisson's ratio in southeastern Tibet from receiver functions.Eos Tran AGU,2005,86(52) :T41A-1283
[8] A Meltzer S Sol,Bürgmann R,van der Hilst R D,et al.Geodynamics of the southeastern Tibetan Plateau from seismic anisotropy and geodesy.Geology,2007,35(6) :563-586
[9] Hu J F,Su Y J,Zhu X G,et al.S-wave velocity and Poisson's ratio structure of crust in Yunnan and its implication.Science in China(Series D-Earth Sciences)(in Chinese),2003,33(8) :714-722
[10] Ji S,Wang Q,Salisbury M H.Composition and tectonic evolution of the Chinese continental crust constrained by Poisson's ratio.Tectonophysics,2008,doi:10． 1016/j.tecto.2008． 09． 007
[11] YuanX,Ni J,Kind R,et al.Lithospheric and upper mantle structure of southern Tibet from a seismological passive source experiment.J.Geophys.Res.,1997,102(B12) :27491-27500
[12] Li X,Yuan X.Receiver functions in northeast China-implications for slab penetration into the lower mantle in northwest Pacific subduction zone.Earth Planet.Sci.Lett.,2003,216:679-691
[13] Kumar P,Yuan X,Kind R,et al.The lithosphere-asthenosphere boundary in the Tien Shan-Karakoram region from S receiver functions:Evidence for continental subduction.Geophys.Res.Lett.,2005,32,L07305,doi:10． 1029/2004GL022291
[14] Kumar P,Kind R,Hanka W,et al.The lithosphere-asthenosphere boundary in the North-West Atlantic region.Earth Planet.Sci.Lett.,2005,236:249-257,doi:10． 1016/j.epsl.2005． 05． 029
[15] Yuan X,Kind R,Li X,et al.The S receiver functions:synthetics and data example.Geophys.J.Int.,2006,165 (2) :555-564,doi:10． 1111/j.1365-246X.2006． 02885． x
[16] Yuan X,Sobolev S V,Kind R.Moho topography in the central Andes and its geodynamic implications.Earth Planet.Sci.Lett.,2002,199:389-402
[17] Kind R,Yuan X,Saul J,et al.Seismic images of crust and upper mantle beneath Tibet;evidence for Eurasian plate subduction.Science,2002,298:1219-1221
[18] Oreshin S,Kiselev S,Vinnik L,et al.Crust and mantle beneath western Himalaya,Ladakh and western Tibet from integrated seismic data.Earth Planet.Sci.Lett.,2008,271:75-87
[19] Shen X,Zhou H,Kawakatsu K.Mapping the upper mantle discontinuities beneath China with teleseismic receiver functions.Earth Planets Space,2008,60,713-719
[20] Li C,van der Hilst R D,Meltzer A S,et al.Subduction of the Indian Jithosphere beneath the Tibetan Plateau and Burma.Earth Planet.Sci.Lett.,2008,274:157-168
[2] Xu L,Rondenay S,van der Hilst R D.Strucure of the crust beneath the southeastern Tibetan Plateau from teleseismic receiver functions.Physics of the Earth and Planetary Interiors,2007,165:176-193
[3] 滕吉文,白登海,杨辉等.2008汶川Ms8． 0地震发生的深层过程和动力学响应.地球物理学报,2008,51(5) :1385-1402 Yao H.van der Hilst R D,De Hoop M V.Surface-wave array tomography in SE Tibet from ambient seismic noise and two-station analysis:Ⅰ-Phase velocity maps.Geophys.J.Int.,2006,166:732-744
[5] 楼海,王椿镛,吕智勇等.2008年汶川Ms8． 0级地震的深部构造环境--远震P波接收函数和布格重力异常的联合解释.中国科学(D辑:地球科学),2008,38(10) :1207-1220 Lou H,Wang C Y,Lü Z Y,et al.Deep tectonic environment of the Wenchuan M_s 8． 0 earthquake of 2008． -Joint interpretation of P receiver functions and Bouguer gravity anomalies.Science in China (Series D-Earth Sciences),2008,38(10) :1207-1220
[6] Wang C Y,Lou H,Lü Z,et al.S-wave crustal and upper mantle's velocity structure in the eastern Tibetan Plateau-Deep environment of lower crustal flow.Science in China (Series D-Earth Sciences),2008,51 (2) :263-274
[7] Zurek B D,Meltzer A,Sol S,et al.Measurements of crustal thickness and Poisson's ratio in southeastern Tibet from receiver functions.Eos Tran AGU,2005,86(52) :T41A-1283
[8] A Meltzer S Sol,Bürgmann R,van der Hilst R D,et al.Geodynamics of the southeastern Tibetan Plateau from seismic anisotropy and geodesy.Geology,2007,35(6) :563-586
[9] Hu J F,Su Y J,Zhu X G,et al.S-wave velocity and Poisson's ratio structure of crust in Yunnan and its implication.Science in China(Series D-Earth Sciences)(in Chinese),2003,33(8) :714-722
[10] Ji S,Wang Q,Salisbury M H.Composition and tectonic evolution of the Chinese continental crust constrained by Poisson's ratio.Tectonophysics,2008,doi:10． 1016/j.tecto.2008． 09． 007
[11] YuanX,Ni J,Kind R,et al.Lithospheric and upper mantle structure of southern Tibet from a seismological passive source experiment.J.Geophys.Res.,1997,102(B12) :27491-27500
[12] Li X,Yuan X.Receiver functions in northeast China-implications for slab penetration into the lower mantle in northwest Pacific subduction zone.Earth Planet.Sci.Lett.,2003,216:679-691
[13] Kumar P,Yuan X,Kind R,et al.The lithosphere-asthenosphere boundary in the Tien Shan-Karakoram region from S receiver functions:Evidence for continental subduction.Geophys.Res.Lett.,2005,32,L07305,doi:10． 1029/2004GL022291
[14] Kumar P,Kind R,Hanka W,et al.The lithosphere-asthenosphere boundary in the North-West Atlantic region.Earth Planet.Sci.Lett.,2005,236:249-257,doi:10． 1016/j.epsl.2005． 05． 029
[15] Yuan X,Kind R,Li X,et al.The S receiver functions:synthetics and data example.Geophys.J.Int.,2006,165 (2) :555-564,doi:10． 1111/j.1365-246X.2006． 02885． x
[16] Yuan X,Sobolev S V,Kind R.Moho topography in the central Andes and its geodynamic implications.Earth Planet.Sci.Lett.,2002,199:389-402
[17] Kind R,Yuan X,Saul J,et al.Seismic images of crust and upper mantle beneath Tibet;evidence for Eurasian plate subduction.Science,2002,298:1219-1221
[18] Oreshin S,Kiselev S,Vinnik L,et al.Crust and mantle beneath western Himalaya,Ladakh and western Tibet from integrated seismic data.Earth Planet.Sci.Lett.,2008,271:75-87
[19] Shen X,Zhou H,Kawakatsu K.Mapping the upper mantle discontinuities beneath China with teleseismic receiver functions.Earth Planets Space,2008,60,713-719
[20] Li C,van der Hilst R D,Meltzer A S,et al.Subduction of the Indian Jithosphere beneath the Tibetan Plateau and Burma.Earth Planet.Sci.Lett.,2008,274:157-168
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