二维部分熔融花岗岩波速的有限元模拟
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摘要
本文采用热弹性有限元数值模拟方法,计算二维情况下部分熔融花岗岩的纵波速度(Vp),分析熔体含量及熔体分布形态对于花岗岩纵波速度的影响.模拟结果表明花岗岩的Vp随着熔体含量的增加而降低,当熔体含量为7%～13%时,Vp可降至5.6～5.8km/s.熔体的形状对于Vp也有影响,当熔体以菱形形状分布于岩石中时,沿菱形长轴方向Vp减小幅度更大,在熔体含量达到15%时,沿菱形长轴方向的Vp减小达到20%,而在短轴方向仅4%.当熔体聚集成条带时,不同方向得到的Vp呈现明显的差异,表明熔体的定向排列不仅会使纵波速度呈现大幅度的减小,而且会引起地震波的各向异性.
In this paper,we calculate the Vp of 2D partially molten granite using thermal elastic finite element simulation,to study how the melt content and the melt shape to affect the granite wave velocity.The results show Vp decreases with the melt content,and Vp reduces to 5.6~5.8 km/s when the melt content is 7%~13%.The melt shape also effects the Vp.When the melt distributes randomly in the rock as rhombus,Vp decreases more quickly along the long axis.Vp decreases by 20% along the long axis as the melt content is 15%,while only 4% along the short axis.Vp of the partially molten aggregate varies with the directions.It shows that the partially molten aggregate not only decreases the Vp more quickly,but also lead to the seismic wave anisotropy.
In this paper,we calculate the Vp of 2D partially molten granite using thermal elastic finite element simulation,to study how the melt content and the melt shape to affect the granite wave velocity.The results show Vp decreases with the melt content,and Vp reduces to 5.6~5.8 km/s when the melt content is 7%~13%.The melt shape also effects the Vp.When the melt distributes randomly in the rock as rhombus,Vp decreases more quickly along the long axis.Vp decreases by 20% along the long axis as the melt content is 15%,while only 4% along the short axis.Vp of the partially molten aggregate varies with the directions.It shows that the partially molten aggregate not only decreases the Vp more quickly,but also lead to the seismic wave anisotropy.
引文
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[11]黄立言,卢德源,赵文津,等.藏南帕里至达吉地带的上地壳结构特征-REFTEK顺带广角地震观测结果分析[J].地球学报-中国地质科学院院报,1996,17(2):165-176.Huang L Y,Lu D Y,Zhao W J,et al.The upper crustalstructure of the Area from Pagri to Dagyi in the southernTibet from Piggyback Reftek wide-angle seismic data[J].Acta Geoscientia Sinica(in Chinese),1996,17(2):165-176.
[12]Watanabe T.Effects of water and melt on seismic velocitiesand their application to characterization of seismic reflectors[J].Geophysical Research Letter,1993,20(24):2933-2936.
[13]Nelson K D,Zhao W,Brown L D,et al.Partially moltenmiddle crust beneath southern Tibet:Synthesis of projectINDEPTH results[J].Science,1996,274(5293):1684-1688.
[14]Kind R,Ni J,Zhao W,et al.Evidence from earthquake datafor a partially molten crustal layer in southern Tibet[J].Science,1996,274(5293):1692-1694.
[15]Schmitz M,Heinsohn W D,Schilling F R.Seismic,gravityand petrological evidence for partial melt beneath thethickened Central Andean crust(21–23°S)[J].Tectonophysics,1997,270(3/4):313-326.
[16]刘永祥,吴福元,张世红.高温高压下岩石弹性波速特征及其在深部地质研究中的意义[J].地球物理学进展,1995,10(3):82-94.Liu Y X,Wu F Y,Zhang S H.The characteristics of elasticwave velocity of rocks at high T and P:implications for thestudy of deepseated geology[J].Progress in Geophysics(inChinese),1995,10(3):82-94.
[17]刘永祥,伍旭光.高温高压下岩石波速与地壳深部的物质组成[J].地球物理学报,1997,40(2):211-220.Liu Y X,Wu X G.Wave velocity in rocks under hightemperature and pressure and composition of the deep crust[J].Chinese J.Geophys.(in Chinese),1997,40(2):211-220.
[18]马麦宁,白武明.高温高压实验弹性波速研究及其地球动力学意义[J].地球物理学进展,1999,14(1):40-55.Ma M N,Bai W M.Progress of high temperature andpressure study on elastic wave velocity and its geodynamicalimplications[J].Progress in Geophysics(in Chinese),1999,14(1):40-55.
[19]马麦宁,白武明,伍向阳.10.6～1.5GPa、室温～1200℃条件下青藏高原地壳岩石弹性波速特征[J].地球物理学进展,2002,17(4):684-689.Ma M N,Bai W M,Wu X Y.Study on elastic wavevelocities of crustal rocks under high temperature and highpressure conditions[J].Progress in Geophyscis(in Chinese),2002,17(4):684-689.
[20]Murase T,Kushiro I.Compressional Wave Velocity inPartially Molten Peridotite at High Pressure[M].Washington:Carnegie Institution of Washington,1979,78:559-562.
[21]Sato H,Sacks I S,Murase T.The use of laboratory velocitydata for estimating temperature and partial melt fraction inthe low-velocity zone:Comparison with heat flow andelectrical conductivity studies[J].Journal of GeophysicalResearch,1989,94(B5):5689-5704.
[22]Müellor H J,Raab S.Elastic wave velocities of granite atexperimental simulated partial melting conditions[J].Physicsand Chemistry of the Earth,1997,22(1/2):93-96.
[23]白武明,马麦宁,柳江琳.地壳岩石波速和电导率实验研究[J].岩石力学与工程学报,2000,19(增):899-904.Bai W M,Ma M N,Liu J L.Testing study on elastic wavevelocities and electrical conductivity of crustal rocks[J].Chinese Journal of Rock Mechanics and Engineering(inChinese),2000,19(S1):899-904.
[24]孔祥谦.热应力有限单元法分析[M].上海:上海交通大学出版社,1999.Kong X Q.The Thermal Stress Analysis Using FiniteElement Method[M](in Chinese).Shanghai:ShanghaiJiaotong University Press,1999.
[25]Wyllie,M R J,Gregory A R,Gardner L W.Elastic wavevelocities in heterogeneous and porous media[J].Geophysics,1956,21(1):41-70.
[26]OzacarA A,Zandt G.Crustal seismic anisotropy in centralTibet:Implications for deformational style and flow in thecrust[J].Geophysical Research Letter,2004,31:L23601,doi:1011029/2004GL021096.
[27]Sherrington H F,Zandt G,Frederiksen A.Crustal fabric inthe Tibetan Plateau based on waveform inversions for seismicanisotropy parameters[J].Journal of Geophysical Research,2004,109:B02312,doi:1029/2002JB002345.
[28]Shapiro N M,Ritzwoller M H,Molnar P,et al.Thinningand flow of Tibetan crust constrained by seismic anisotropy[J].Science,2004,305(5681):233-236.
[29]Kohlstedt D L,Zimmerman M E.Rheology of partiallymolten mantle rocks[J].Annual Review of Earth andPlanetary Sciences,1996,24(1):41-62.
[30]Katz R F,Spiegeiman M,Holtman B.The dynamics of meltand shear localization in partially molten aggregates[J].Nature,2006,442(7103):676-679.
[2]胡家富,苏有锦,朱雄关,等.云南的地壳S波速度与泊松比结构及其意义[J].中国科学D辑:地球科学,2003,33(8):714-722.Hu J F,Su Y J,Zhu X G,et al.S waves speed and poissonratio and their significance in Yunnan crust[J].Science inChina Series(D:Earth Sciences)(in Chinese),2003,33(8):714-722.
[3]卢占武,高锐,李秋生,等.中国青藏高原深部地球物理探测与地球动力学研究(1958-2004)[J].地球物理学报,2006,49(3):753-770.Lu Z W,Gao R,Li Q S,et al.Deep geophysical probe andgeodynamic study on the Qinghai-Tibet Plateau(1958-2004)[J].Chinese J.Geophys.(in Chinese),2006,49(3):753-770.
[4]郭飚,刘启元,陈九辉,等.青藏高原东北缘-鄂尔多斯地壳上地幔地震层析成像研究[J].地球物理学报,2004,47(5):790-797.Guo B,Liu Q Y,Chen J H,et al.Seismic tomographicimaging of the crust and upper mantle beneath theNortheastern edge of the Qinghai-Xizang plateau and the Ordosarea[J].Chinese J.Geophys.(in Chinese),2004,47(5):790-797.
[5]Rapine R,Tillman T,West M,et al.Crustal structure ofnorthern and southern Tibet from surface wave dispersionanalysis[J].J.Geophys.Res.,2003,108(B2):2120,doi:10.1029/2001JB000445.
[6]陈运泰,等.中国大陆地震学与地球内部物理学研究进展[M].北京:地震出版社,2004:295-310.Zhu LP.Lateral Variation of the Tibetan LithosphericStructure Inferred from Teleseismic Waveforms[M](inChinese).Beijing:The Earthquake Press,2004:295-310.
[7]佟伟,章铬陶,等.西藏地热[M].北京:科学出版社,1981.Tong W,Zhang L T,et al.Geotherm in Tibet[M](inChinese).Beijing:Science Press,1981.
[8]沈显杰,张文仁,杨淑贞,等.西藏热流数据最新报道[J].科学通报,1989,(5):373-376.Shen X J,Zhang W R,Yang S Z,et al.Updated report onheat flow data in Xizang[J].Chinese Science Bulletin,1989,34(20):1728-1732.
[9]沈显杰,张文仁,杨淑贞,等.青藏高原南北地体壳幔热结构差异的大地热流证据[J].中国地质科学院院报,1990,(2):203-214.Shen X J,Zhang W R,Yang S Z,et al.Heat flow evidencefor the differentiated crust-mantle thermal structures of thenorthern and southern terranes of the Qinghai-Xizang Plateau[J].Acta Geosicientia Sinica(in Chinese),1990,(2):203-214.
[10]沈显杰.从藏南高热流的形成机理推论西藏地壳和上地幔热结构[J].地球物理学报,1985,28(增):93-107.Shen X J.Infer Tibet crust and upper mantle hot structurefrom the south Tibetan high heat flux of the formationmechanism[J].Chinese J.Geophys.(in Chinese),1985,28:93-107.
[11]黄立言,卢德源,赵文津,等.藏南帕里至达吉地带的上地壳结构特征-REFTEK顺带广角地震观测结果分析[J].地球学报-中国地质科学院院报,1996,17(2):165-176.Huang L Y,Lu D Y,Zhao W J,et al.The upper crustalstructure of the Area from Pagri to Dagyi in the southernTibet from Piggyback Reftek wide-angle seismic data[J].Acta Geoscientia Sinica(in Chinese),1996,17(2):165-176.
[12]Watanabe T.Effects of water and melt on seismic velocitiesand their application to characterization of seismic reflectors[J].Geophysical Research Letter,1993,20(24):2933-2936.
[13]Nelson K D,Zhao W,Brown L D,et al.Partially moltenmiddle crust beneath southern Tibet:Synthesis of projectINDEPTH results[J].Science,1996,274(5293):1684-1688.
[14]Kind R,Ni J,Zhao W,et al.Evidence from earthquake datafor a partially molten crustal layer in southern Tibet[J].Science,1996,274(5293):1692-1694.
[15]Schmitz M,Heinsohn W D,Schilling F R.Seismic,gravityand petrological evidence for partial melt beneath thethickened Central Andean crust(21–23°S)[J].Tectonophysics,1997,270(3/4):313-326.
[16]刘永祥,吴福元,张世红.高温高压下岩石弹性波速特征及其在深部地质研究中的意义[J].地球物理学进展,1995,10(3):82-94.Liu Y X,Wu F Y,Zhang S H.The characteristics of elasticwave velocity of rocks at high T and P:implications for thestudy of deepseated geology[J].Progress in Geophysics(inChinese),1995,10(3):82-94.
[17]刘永祥,伍旭光.高温高压下岩石波速与地壳深部的物质组成[J].地球物理学报,1997,40(2):211-220.Liu Y X,Wu X G.Wave velocity in rocks under hightemperature and pressure and composition of the deep crust[J].Chinese J.Geophys.(in Chinese),1997,40(2):211-220.
[18]马麦宁,白武明.高温高压实验弹性波速研究及其地球动力学意义[J].地球物理学进展,1999,14(1):40-55.Ma M N,Bai W M.Progress of high temperature andpressure study on elastic wave velocity and its geodynamicalimplications[J].Progress in Geophysics(in Chinese),1999,14(1):40-55.
[19]马麦宁,白武明,伍向阳.10.6～1.5GPa、室温～1200℃条件下青藏高原地壳岩石弹性波速特征[J].地球物理学进展,2002,17(4):684-689.Ma M N,Bai W M,Wu X Y.Study on elastic wavevelocities of crustal rocks under high temperature and highpressure conditions[J].Progress in Geophyscis(in Chinese),2002,17(4):684-689.
[20]Murase T,Kushiro I.Compressional Wave Velocity inPartially Molten Peridotite at High Pressure[M].Washington:Carnegie Institution of Washington,1979,78:559-562.
[21]Sato H,Sacks I S,Murase T.The use of laboratory velocitydata for estimating temperature and partial melt fraction inthe low-velocity zone:Comparison with heat flow andelectrical conductivity studies[J].Journal of GeophysicalResearch,1989,94(B5):5689-5704.
[22]Müellor H J,Raab S.Elastic wave velocities of granite atexperimental simulated partial melting conditions[J].Physicsand Chemistry of the Earth,1997,22(1/2):93-96.
[23]白武明,马麦宁,柳江琳.地壳岩石波速和电导率实验研究[J].岩石力学与工程学报,2000,19(增):899-904.Bai W M,Ma M N,Liu J L.Testing study on elastic wavevelocities and electrical conductivity of crustal rocks[J].Chinese Journal of Rock Mechanics and Engineering(inChinese),2000,19(S1):899-904.
[24]孔祥谦.热应力有限单元法分析[M].上海:上海交通大学出版社,1999.Kong X Q.The Thermal Stress Analysis Using FiniteElement Method[M](in Chinese).Shanghai:ShanghaiJiaotong University Press,1999.
[25]Wyllie,M R J,Gregory A R,Gardner L W.Elastic wavevelocities in heterogeneous and porous media[J].Geophysics,1956,21(1):41-70.
[26]OzacarA A,Zandt G.Crustal seismic anisotropy in centralTibet:Implications for deformational style and flow in thecrust[J].Geophysical Research Letter,2004,31:L23601,doi:1011029/2004GL021096.
[27]Sherrington H F,Zandt G,Frederiksen A.Crustal fabric inthe Tibetan Plateau based on waveform inversions for seismicanisotropy parameters[J].Journal of Geophysical Research,2004,109:B02312,doi:1029/2002JB002345.
[28]Shapiro N M,Ritzwoller M H,Molnar P,et al.Thinningand flow of Tibetan crust constrained by seismic anisotropy[J].Science,2004,305(5681):233-236.
[29]Kohlstedt D L,Zimmerman M E.Rheology of partiallymolten mantle rocks[J].Annual Review of Earth andPlanetary Sciences,1996,24(1):41-62.
[30]Katz R F,Spiegeiman M,Holtman B.The dynamics of meltand shear localization in partially molten aggregates[J].Nature,2006,442(7103):676-679.
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