利用多层横波各向异性测量方法计算两层介质的分裂参数
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摘要
对实际两层各向异性介质,在一层假设条件下利用Silver和Chan(1991)的等效单层各向异性测量方法,以及在两层假设条件下利用剥去法和反演法,计算模型的分裂参数.首先利用理论雷克子波得到经过两层各向异性的观测数据,然后加入噪声之前和之后,分别计算不同反方位角覆盖条件下数据的各向异性,并与理论模型的分裂参数进行比较.结果发现在上层分裂特征已知的基础上,剥去法适用于任何模型,不管是否存在分裂,或者分裂特征在两层中如何分布;而反演法更适用于两层各向异性较强且不同的模型,其结果受噪声和方位角分布的影响.选取不同方位角分布的高信噪比数据,比较剥去法和反演法对下层分裂参数的计算结果,发现当入射方位角在两层快波方向之间时,反演结果比较可靠.最后利用这三种测量各向异性的方法,计算青藏高原东南缘CEArray台站观测到的SKS数据中记录的各向异性.除了云贵高原的台站YN.CUX表现出较明显的两层分裂特征,大部分台站下的岩石圈各向异性呈现一层或者较弱的各向异性.于是针对该台站,用反演法同时对这两层的分裂参数进行估计,上层的结果与接收函数计算的地壳分裂参数一致;下层的结果与剥去法计算的上地幔分裂参数一致,说明反演法同剥去法一样,都能有效的分析具有两层各向异性特征的介质.
For a two-layer anisotropic medium,we calculated the splitting parameters of the model,by using three different measurement methods:(1)the traditional one-layer estimating method of Silver and Chan(1991),(2)the top-layer stripping-off method,and(3)a simultaneous gridding search method.We generated a large waveform dataset for a total of 8 models using the Ricker wavelet as the source wavelet.We then investigated how well these three methods can recover the input models under different noise and limited backazimuthal coverage conditions.Our numerical tests indicate that the top-layer stripping-off method can recover the input models even when the data are from a narrow azimuthal range and have the level of noise in real data.In contrast,the grid-search based inversion method is more suitable for models with the fast directions of the two layers being a few tens of degrees away from each other.We also applied these three methods to the SKS waveform data recorded by 13 CEArray stations at the southeastern margin of Tibetan plateau.We found that the SKS data recorded by the YN.CUX station on the Yunnan-Guizhou plateau exhibit obvious two-layer splitting characteristics,while those from the other stations seem to be well explained by a one-layer anisotropic model.
For a two-layer anisotropic medium,we calculated the splitting parameters of the model,by using three different measurement methods:(1)the traditional one-layer estimating method of Silver and Chan(1991),(2)the top-layer stripping-off method,and(3)a simultaneous gridding search method.We generated a large waveform dataset for a total of 8 models using the Ricker wavelet as the source wavelet.We then investigated how well these three methods can recover the input models under different noise and limited backazimuthal coverage conditions.Our numerical tests indicate that the top-layer stripping-off method can recover the input models even when the data are from a narrow azimuthal range and have the level of noise in real data.In contrast,the grid-search based inversion method is more suitable for models with the fast directions of the two layers being a few tens of degrees away from each other.We also applied these three methods to the SKS waveform data recorded by 13 CEArray stations at the southeastern margin of Tibetan plateau.We found that the SKS data recorded by the YN.CUX station on the Yunnan-Guizhou plateau exhibit obvious two-layer splitting characteristics,while those from the other stations seem to be well explained by a one-layer anisotropic model.
引文
Ansel V,Nataf H C.1989.Anisotropy beneath 9stations of the GEOSCOPE broadband network as deduced from shear-wave splitting.Geophysical Research Letters,16(5):409-412.
Bai D H,Unsworth M J,Meju M A,et al.2010.Crustal deformation of the eastern Tibetan plateau revealed by magnetotelluric imaging.Nature Geoscience,3(5):358-362.
Christensen N I.1984.The magnitude,symmetry and origin of upper mantle anisotropy based on fabric analyses of ultramafic tectonites.Geophysical Journal International,76(1):89-111.
Clark M K,Royden L H.2000.Topographic ooze:Building the eastern margin of Tibet by lower crustal flow.Geology,28(8):703-706.
Clark M K,Schoenbohm L M,Royden L H,et al.2004.Surface uplift,tectonics,and erosion of eastern Tibet from large-scale drainage patterns.Tectonics,23(1):TC1006,doi:10.1029/2002TC001402.
Clark M K,House M A,Royden L H,et al.2005.Late Cenozoic uplift of southeastern Tibet.Geology,33(6):525-528.
Conrad C P,Behn M D,Silver P G.2007.Global mantle flow and the development of seismic anisotropy:differences between the oceanic and continental upper mantle.Journal of Geophysical Research:Solid Earth,112(B7):B07317,doi:10.1029/2006JB004608.
Crampin S.1981.A review of wave motion in anisotropic and cracked elastic-media.Wave Motion,3(4):343-391.
Crampin S,Evans R,Ucer S B.1985.Analysis of records of local earthquakes:The Turkish Dilatancy Projects(TDP1 and TDP2).Geophysical Journal International,83:1-16.
Crampin S,Peacock S.2005.A review of shear-wave splitting in the compliant crack-critical anisotropic Earth.Wave Motion,41(1):59-77.
Granet M,Glahn A,Achauer U.1998.Anisotropic measurements in the Rhinegraben area and the French Massif Central:Geodynamic implications.Pure and Applied Geophysics,151(2-4):333-364.
Hirn A,Diaz J,Sapin M,et al.1998.Variation of shear-wave residuals and splitting parameters from array observations in southern Tibet.Pure and Applied Geophysics,151(2-4):407-431.
Kaneshima S,Silver P G.1992.A search for source side mantle anisotropy.Geophysical Research Letters,19(10):1049-1052.
Kirby E,Reiners P W,Krol M A,et al.2002.Late Cenozoic evolution of the eastern margin of the Tibetan Plateau:Inferences from40 Ar/39 Ar and(U-Th)/He thermochronology.Tectonics,21(1):1001,doi:10.1029/2000TC001246.
Kuo B Y,Forsyth D W.1992.A search for split SKS waveforms in the North Atlantic.Geophysical Journal International,108(2):557-574.
Lei J S,Zhao D P,Su Y J.2009.Insight into the origin of the Tengchong intraplate volcano and seismotectonics in southwest China from local and teleseismic data.Journal of Geophysical Research:SolidEarth,114(B5):B05302,doi:10.1029/2008JB005881.
Lei J S,Zhao D P.2016.Teleseismic P-wave tomography and mantle dynamics beneath Eastern Tibet.Geochemistry,Geophysics,Geosystems,17(5):1861-1884.
Lev E,Long M D,Van Der Hilst R D.2006.Seismic anisotropy in Eastern Tibet from shear wave splitting reveals changes in lithospheric deformation.Earth and Planetary Science Letters,251(3-4):293-304.
Li C,Van Der Hilst R D,Meltzer A S,et al.2008.Subduction of the Indian lithosphere beneath the Tibetan Plateau and Burma.Earth and Planetary Science Letters,274(1-2):157-168.
Long M D,Silver P G.2009.Shear wave splitting and mantle anisotropy:measurements,interpretations,and new directions.Surveys in Geophysics,30(4-5):407-461.
Mainprice D,Silver P G.1993.Interpretation of SKS-waves using samples from the subcontinental lithosphere.Physics of the Earth and Planetary Interiors,78(3-4):257-280.
Mainprice D.2007.Seismic anisotropy of the deep earth from a mineral and rock physics perspective.∥Schubert G ed.Treatise on Geophysics.2nd ed.Amsterdam:Elsevier,2:487-538.
Meissner R,Mooney W D,Artemieva I.2002.Seismic anisotropy and mantle creep in young orogens.Geophysical Journal International,149(1):1-14.
Molnar P,Tapponnier P.1978.Active tectonics of Tibet.Journal of Geophysical Research:Solid Earth,83(B11):5361-5375.
Nur A,Simmons G.1969.Stress-induced velocity anisotropy in rock:an experimental study.Journal of Geophysical Research,74(27):6667-6674.
Ozalaybey S,Savage M K.1994.Double-layer anisotropy resolved fromS phases.Geophysical Journal International,117(3):653-664.
PlomerováJ,Babuska V.2010.Long memory of mantle lithosphere fabric-European LAB constrained from seismic anisotropy.Lithos,120(1-2):131-143.
Rümpker G,Silver P G.1998.Apparent shear-wave splitting parameters in the presence of vertically varying anisotropy.Geophysical Journal International,135(3):790-800.
Romanowicz B,Yuan H Y.2011.On the interpretation of SKSsplitting measurements in the presence of several layers of anisotropy.Geophysical Journal International,188(3):1129-1140.
Royden L H,Burchfiel B C,King R W,et al.1997.Surface deformation and lower crustal flow in eastern Tibet.Science,276(5313):788-790.
Royden L H,Burchfiel B C,Van Der Hilst R D.2008.The geological evolution of the Tibetan Plateau.Science,321(5892):1054-1058.
Russo R M,Silver P G.1994.Trench-parallel flow beneath the Nazca Plate from seismic anisotropy.Science,263(5150):1105-1111.
Savage M,Silver P G.1993.Mantle deformation and tectonics:constraints from seismic anisotropy in the western United States.Physics of the Earth and Planetary Interiors,78(3-4):207-227.
Schoenbohm L M,Burchfiel B C,Chen L Z,et al.2006.Miocene to present activity along the Red River fault,China,in the context of continental extrusion,upper-crustal rotation,and lower-crustal flow.GSA Bulletin,118(5-6):672-688.
Silver P G,Chan W W.1991.Shear wave splitting and subcontinental mantle deformation.Journal of Geophysical Research:Solid Earth,96(B10):16429-16454.
Silver P G,Savage M K.1994.The interpretation of shear-wave splitting parameters in the presence of two anisotropic layers.Geophysical Journal International,119(3):949-963.
Silver P G.1996.Seismic anisotropy beneath the continents:probing the depths of geology.Annual Review of Earth and Planetary Sciences,24:385-432.
Silver P G,Long M D.2011.The non-commutivity of shear wave splitting operators at low frequencies and implications for anisotropy tomography.Geophysical Journal International,184(3):1415-1427.
Sun Y,Niu F L,Liu H F,et al.2012.Crustal structure and deformation of the SE Tibetan plateau revealed by receiver function data.Earth and Planetary Science Letters,349-350:186-197.
Tapponnier P,Meyer B,Avouac J P,et al.1990.Active thrusting and folding in the Qilian Shan,and decoupling between upper crust and mantle in northeastern Tibet.Earth and Planetary Science Letters,97(3-4):382-403.
Wang C Y,Chan W W,Mooney W D.2003.Three-dimensional velocity structure of crust and upper mantle in southwestern China and its tectonic implications.Journal of Geophysical Research,108(B9):2442,doi:10.1029/2002JB001973.
Wang C Y,Lou H,Silver P G,et al.2010.Crustal structure variation along 30°N in the eastern Tibetan Plateau and its tectonic implication.Earth and Planetary Science Letters,289(3-4):367-376.
Wolfe C J,Silver P G.1998.Seismic anisotropy of oceanic upper mantle:shear wave splitting methodologies and observations.Journal of Geophysical Research:Solid Earth,103(B1):749-771.
Yang Y J,Ritzwoller M H,Zheng Y,et al.2012.A synoptic view of the distribution and connectivity of the mid-crustal low velocity zone beneath Tibet.Journal of Geophysical Research:Solid Earth,117(B4):B04303,doi:10.1029/2011JB008810.
Yao C,Hao C T,Zhang G L.2016.A study of synthetic seismograms for SKS-wave response to crustal fractured-induce anisotropy.Chinese Journal of Geophysics(in Chinese),59(7):2498-2509,doi:10.6038/cjg20160715.
Yao H J,Van Der Hilst R D,Montagner J P.2010.Heterogeneity and anisotropy of the lithosphere of SE Tibet from surface wave array tomography.Journal of Geophysical Research:Solid Earth,115(B12):B12307,doi:10.1029/2009JB007142.
Yardley G S,Crampin S.1991.Extensive-dilatancy anisotropy:relative information in VSPs and reflection surveys.Geophysical Prospecting,39(3):337-355.
Zhang J L,Wang Y,Lu J.2013.A new algorithm for frequencydependent shear-wave splitting parameters extraction.Journal of Geophysics and Engineering,10(5):055005,doi:10.1088/1742-2132/10/5/055005.
Zhang J L,Wang Y,Liu Z B,et al.2017.Fracture detection with three dual-scanning shear-wave splitting methods.Oil Geophysical Prospecting(in Chinese),52(1):105-113.
Zhang S Q,Karato S.1995.Lattice preferred orientation of olivine aggregates deformed in simple shear.Nature,375(6534):774-777.
姚陈,郝重涛,张广利.2016.SKS波对地壳裂隙各向异性的响应---理论地震图研究.地球物理学报,59(7):2498-2509,doi:10.6038/cjg20160715.
张建利,王赟,刘志斌等.2017.三种双扫描横波分裂算法在裂缝探测中的应用研究.石油地球物理勘探,52(1):105-113.
Bai D H,Unsworth M J,Meju M A,et al.2010.Crustal deformation of the eastern Tibetan plateau revealed by magnetotelluric imaging.Nature Geoscience,3(5):358-362.
Christensen N I.1984.The magnitude,symmetry and origin of upper mantle anisotropy based on fabric analyses of ultramafic tectonites.Geophysical Journal International,76(1):89-111.
Clark M K,Royden L H.2000.Topographic ooze:Building the eastern margin of Tibet by lower crustal flow.Geology,28(8):703-706.
Clark M K,Schoenbohm L M,Royden L H,et al.2004.Surface uplift,tectonics,and erosion of eastern Tibet from large-scale drainage patterns.Tectonics,23(1):TC1006,doi:10.1029/2002TC001402.
Clark M K,House M A,Royden L H,et al.2005.Late Cenozoic uplift of southeastern Tibet.Geology,33(6):525-528.
Conrad C P,Behn M D,Silver P G.2007.Global mantle flow and the development of seismic anisotropy:differences between the oceanic and continental upper mantle.Journal of Geophysical Research:Solid Earth,112(B7):B07317,doi:10.1029/2006JB004608.
Crampin S.1981.A review of wave motion in anisotropic and cracked elastic-media.Wave Motion,3(4):343-391.
Crampin S,Evans R,Ucer S B.1985.Analysis of records of local earthquakes:The Turkish Dilatancy Projects(TDP1 and TDP2).Geophysical Journal International,83:1-16.
Crampin S,Peacock S.2005.A review of shear-wave splitting in the compliant crack-critical anisotropic Earth.Wave Motion,41(1):59-77.
Granet M,Glahn A,Achauer U.1998.Anisotropic measurements in the Rhinegraben area and the French Massif Central:Geodynamic implications.Pure and Applied Geophysics,151(2-4):333-364.
Hirn A,Diaz J,Sapin M,et al.1998.Variation of shear-wave residuals and splitting parameters from array observations in southern Tibet.Pure and Applied Geophysics,151(2-4):407-431.
Kaneshima S,Silver P G.1992.A search for source side mantle anisotropy.Geophysical Research Letters,19(10):1049-1052.
Kirby E,Reiners P W,Krol M A,et al.2002.Late Cenozoic evolution of the eastern margin of the Tibetan Plateau:Inferences from40 Ar/39 Ar and(U-Th)/He thermochronology.Tectonics,21(1):1001,doi:10.1029/2000TC001246.
Kuo B Y,Forsyth D W.1992.A search for split SKS waveforms in the North Atlantic.Geophysical Journal International,108(2):557-574.
Lei J S,Zhao D P,Su Y J.2009.Insight into the origin of the Tengchong intraplate volcano and seismotectonics in southwest China from local and teleseismic data.Journal of Geophysical Research:SolidEarth,114(B5):B05302,doi:10.1029/2008JB005881.
Lei J S,Zhao D P.2016.Teleseismic P-wave tomography and mantle dynamics beneath Eastern Tibet.Geochemistry,Geophysics,Geosystems,17(5):1861-1884.
Lev E,Long M D,Van Der Hilst R D.2006.Seismic anisotropy in Eastern Tibet from shear wave splitting reveals changes in lithospheric deformation.Earth and Planetary Science Letters,251(3-4):293-304.
Li C,Van Der Hilst R D,Meltzer A S,et al.2008.Subduction of the Indian lithosphere beneath the Tibetan Plateau and Burma.Earth and Planetary Science Letters,274(1-2):157-168.
Long M D,Silver P G.2009.Shear wave splitting and mantle anisotropy:measurements,interpretations,and new directions.Surveys in Geophysics,30(4-5):407-461.
Mainprice D,Silver P G.1993.Interpretation of SKS-waves using samples from the subcontinental lithosphere.Physics of the Earth and Planetary Interiors,78(3-4):257-280.
Mainprice D.2007.Seismic anisotropy of the deep earth from a mineral and rock physics perspective.∥Schubert G ed.Treatise on Geophysics.2nd ed.Amsterdam:Elsevier,2:487-538.
Meissner R,Mooney W D,Artemieva I.2002.Seismic anisotropy and mantle creep in young orogens.Geophysical Journal International,149(1):1-14.
Molnar P,Tapponnier P.1978.Active tectonics of Tibet.Journal of Geophysical Research:Solid Earth,83(B11):5361-5375.
Nur A,Simmons G.1969.Stress-induced velocity anisotropy in rock:an experimental study.Journal of Geophysical Research,74(27):6667-6674.
Ozalaybey S,Savage M K.1994.Double-layer anisotropy resolved fromS phases.Geophysical Journal International,117(3):653-664.
PlomerováJ,Babuska V.2010.Long memory of mantle lithosphere fabric-European LAB constrained from seismic anisotropy.Lithos,120(1-2):131-143.
Rümpker G,Silver P G.1998.Apparent shear-wave splitting parameters in the presence of vertically varying anisotropy.Geophysical Journal International,135(3):790-800.
Romanowicz B,Yuan H Y.2011.On the interpretation of SKSsplitting measurements in the presence of several layers of anisotropy.Geophysical Journal International,188(3):1129-1140.
Royden L H,Burchfiel B C,King R W,et al.1997.Surface deformation and lower crustal flow in eastern Tibet.Science,276(5313):788-790.
Royden L H,Burchfiel B C,Van Der Hilst R D.2008.The geological evolution of the Tibetan Plateau.Science,321(5892):1054-1058.
Russo R M,Silver P G.1994.Trench-parallel flow beneath the Nazca Plate from seismic anisotropy.Science,263(5150):1105-1111.
Savage M,Silver P G.1993.Mantle deformation and tectonics:constraints from seismic anisotropy in the western United States.Physics of the Earth and Planetary Interiors,78(3-4):207-227.
Schoenbohm L M,Burchfiel B C,Chen L Z,et al.2006.Miocene to present activity along the Red River fault,China,in the context of continental extrusion,upper-crustal rotation,and lower-crustal flow.GSA Bulletin,118(5-6):672-688.
Silver P G,Chan W W.1991.Shear wave splitting and subcontinental mantle deformation.Journal of Geophysical Research:Solid Earth,96(B10):16429-16454.
Silver P G,Savage M K.1994.The interpretation of shear-wave splitting parameters in the presence of two anisotropic layers.Geophysical Journal International,119(3):949-963.
Silver P G.1996.Seismic anisotropy beneath the continents:probing the depths of geology.Annual Review of Earth and Planetary Sciences,24:385-432.
Silver P G,Long M D.2011.The non-commutivity of shear wave splitting operators at low frequencies and implications for anisotropy tomography.Geophysical Journal International,184(3):1415-1427.
Sun Y,Niu F L,Liu H F,et al.2012.Crustal structure and deformation of the SE Tibetan plateau revealed by receiver function data.Earth and Planetary Science Letters,349-350:186-197.
Tapponnier P,Meyer B,Avouac J P,et al.1990.Active thrusting and folding in the Qilian Shan,and decoupling between upper crust and mantle in northeastern Tibet.Earth and Planetary Science Letters,97(3-4):382-403.
Wang C Y,Chan W W,Mooney W D.2003.Three-dimensional velocity structure of crust and upper mantle in southwestern China and its tectonic implications.Journal of Geophysical Research,108(B9):2442,doi:10.1029/2002JB001973.
Wang C Y,Lou H,Silver P G,et al.2010.Crustal structure variation along 30°N in the eastern Tibetan Plateau and its tectonic implication.Earth and Planetary Science Letters,289(3-4):367-376.
Wolfe C J,Silver P G.1998.Seismic anisotropy of oceanic upper mantle:shear wave splitting methodologies and observations.Journal of Geophysical Research:Solid Earth,103(B1):749-771.
Yang Y J,Ritzwoller M H,Zheng Y,et al.2012.A synoptic view of the distribution and connectivity of the mid-crustal low velocity zone beneath Tibet.Journal of Geophysical Research:Solid Earth,117(B4):B04303,doi:10.1029/2011JB008810.
Yao C,Hao C T,Zhang G L.2016.A study of synthetic seismograms for SKS-wave response to crustal fractured-induce anisotropy.Chinese Journal of Geophysics(in Chinese),59(7):2498-2509,doi:10.6038/cjg20160715.
Yao H J,Van Der Hilst R D,Montagner J P.2010.Heterogeneity and anisotropy of the lithosphere of SE Tibet from surface wave array tomography.Journal of Geophysical Research:Solid Earth,115(B12):B12307,doi:10.1029/2009JB007142.
Yardley G S,Crampin S.1991.Extensive-dilatancy anisotropy:relative information in VSPs and reflection surveys.Geophysical Prospecting,39(3):337-355.
Zhang J L,Wang Y,Lu J.2013.A new algorithm for frequencydependent shear-wave splitting parameters extraction.Journal of Geophysics and Engineering,10(5):055005,doi:10.1088/1742-2132/10/5/055005.
Zhang J L,Wang Y,Liu Z B,et al.2017.Fracture detection with three dual-scanning shear-wave splitting methods.Oil Geophysical Prospecting(in Chinese),52(1):105-113.
Zhang S Q,Karato S.1995.Lattice preferred orientation of olivine aggregates deformed in simple shear.Nature,375(6534):774-777.
姚陈,郝重涛,张广利.2016.SKS波对地壳裂隙各向异性的响应---理论地震图研究.地球物理学报,59(7):2498-2509,doi:10.6038/cjg20160715.
张建利,王赟,刘志斌等.2017.三种双扫描横波分裂算法在裂缝探测中的应用研究.石油地球物理勘探,52(1):105-113.
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