帕米尔—兴都库什深俯冲残留体对410km间断面起伏形态的影响
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摘要
受俯冲残留体影响的410km间断面起伏形态的研究对于确定地球内部物质构成及地球动力学过程具有重要作用.帕米尔—兴都库什俯冲区域拥有全球少有的中、深源地震,为研究410km间断面起伏提供了良好的资源.利用日本Hi-net地震台网和美国TA台阵记录的帕米尔—兴都库什俯冲区域的6个震源深度为154.0~220.9km、震级为Mb5.6~6.4的中、深源地震的短周期/宽频带波形资料,经过4次根倾斜叠加处理,获得了36组Hi-net子台网和TA记录资料的倾斜叠加灰度图,从中提取了与410km间断面相关的次生转换震相SdP,发现受俯冲残留体影响下的410km间断面的深度位于372~398km.较之持续俯冲的西太平洋地区海洋岩石圈,研究区域俯冲滞留体对于410km间断面的相变线的影响要小得多.
The effects of stagnant slabs on the topography of the 410 km discontinuity is helpful in determining the composition of Earth′s interior and understanding the related geodynamical process.The different stages of subduction can introduce different temperature and material anomalies on mantle discontinuities.Comparing with the subducting slabs around the western Pacific regions,the subducted oceanic lithosphere beneath the Pamir-Hindu Kush should have less effects on the phase transition of mantle discontinuities.Pamir-Hindu Kush is a rare subduction region with a lot of mid-deep earthquakes.Broadband/short period waveform data of6 earthquakes in the subducted slabs beneath Pamir-Hindu Kush,whose focal depths are between154.0~220.9km and magnitudes are between Mb5.6~6.4,recorded by Hi-net seismic network,Japan,and one event among them by the TA seismic array,USA,were processed with the 4-th root slant stack method.36 vespegrams deduced from the observed waveform data from Hi-net subnetworks and the TA array were used to obtain the conversion phase SdP,then the conversion depths around 410 km were determined based on IASP91.For the Ev.4,the conversion points picked from the vespegrams of Hi-net at the epicentral distances of 40°~50°and the TA at about 95°respectively show almost the same conversion depths at 390 km and which means that the conversion depths from different sub-networks of Hinet and TA array are consistent.Based on the distribution of 36 conversion points around the depth of 410 km related to picked SdP phases,the 410 km discontinuity is uplifted to the depths between 372~398km and has relatively complicated structure.Assuming the Clapeyron slope as-2.9 MPa/K(Bina and Helffrich,1994),the subducted slabs cause a low temperature anomaly about 250 to 360K.Combining with geological and geochemical results,the continent-continent collision of Pamir-Hindu Kush happened at 102~85 Ma(Ali et al.,2002),so the stagnant materials of subducted slabs have been warmed up since then.The stagnant materials including the garnet and pyroxene,and some volatiles make the 410 km discontinuity structure complicated.Because of long-period warming-up process of the subducted slabs beneath Pamir-Hindu Kush,the stagnant materials have less impacts on the 410 km discontinuity than those from subducting slabs around the western Pacific region where the discontinuity is up-lifted by 60~70km(e.g.,Collier and Helffrich,1997;Collier et al.,2001).36 vespegrams deduced from the observed waveform data of Hi-net sub-networks and the TA array of 6 mid-deep events beneath PamirHindu Kush were used to retrieve the conversion phases SdP caused by the 410 km discontinuity.The conversion depths around 410 km were determined based on IASP91.From the distribution of conversion points,the 410 km discontinuity is up-lifted to the depths around 372~398km caused by the long-period warming-up stagnant materials from the subducted oceanic lithosphere.Comparing with the western Pacific subducting slabs,the subducted stagnancy has less impacts on the topography of the 410 discontinuity.
The effects of stagnant slabs on the topography of the 410 km discontinuity is helpful in determining the composition of Earth′s interior and understanding the related geodynamical process.The different stages of subduction can introduce different temperature and material anomalies on mantle discontinuities.Comparing with the subducting slabs around the western Pacific regions,the subducted oceanic lithosphere beneath the Pamir-Hindu Kush should have less effects on the phase transition of mantle discontinuities.Pamir-Hindu Kush is a rare subduction region with a lot of mid-deep earthquakes.Broadband/short period waveform data of6 earthquakes in the subducted slabs beneath Pamir-Hindu Kush,whose focal depths are between154.0~220.9km and magnitudes are between Mb5.6~6.4,recorded by Hi-net seismic network,Japan,and one event among them by the TA seismic array,USA,were processed with the 4-th root slant stack method.36 vespegrams deduced from the observed waveform data from Hi-net subnetworks and the TA array were used to obtain the conversion phase SdP,then the conversion depths around 410 km were determined based on IASP91.For the Ev.4,the conversion points picked from the vespegrams of Hi-net at the epicentral distances of 40°~50°and the TA at about 95°respectively show almost the same conversion depths at 390 km and which means that the conversion depths from different sub-networks of Hinet and TA array are consistent.Based on the distribution of 36 conversion points around the depth of 410 km related to picked SdP phases,the 410 km discontinuity is uplifted to the depths between 372~398km and has relatively complicated structure.Assuming the Clapeyron slope as-2.9 MPa/K(Bina and Helffrich,1994),the subducted slabs cause a low temperature anomaly about 250 to 360K.Combining with geological and geochemical results,the continent-continent collision of Pamir-Hindu Kush happened at 102~85 Ma(Ali et al.,2002),so the stagnant materials of subducted slabs have been warmed up since then.The stagnant materials including the garnet and pyroxene,and some volatiles make the 410 km discontinuity structure complicated.Because of long-period warming-up process of the subducted slabs beneath Pamir-Hindu Kush,the stagnant materials have less impacts on the 410 km discontinuity than those from subducting slabs around the western Pacific region where the discontinuity is up-lifted by 60~70km(e.g.,Collier and Helffrich,1997;Collier et al.,2001).36 vespegrams deduced from the observed waveform data of Hi-net sub-networks and the TA array of 6 mid-deep events beneath PamirHindu Kush were used to retrieve the conversion phases SdP caused by the 410 km discontinuity.The conversion depths around 410 km were determined based on IASP91.From the distribution of conversion points,the 410 km discontinuity is up-lifted to the depths around 372~398km caused by the long-period warming-up stagnant materials from the subducted oceanic lithosphere.Comparing with the western Pacific subducting slabs,the subducted stagnancy has less impacts on the topography of the 410 discontinuity.
引文
Ali A,Nakamura E,Yamamoto H.2002.Sm-Nd mineral ages ofpegmatite veins and their host rocks from Swat area,Chilascomplex,northern Pakistan.J.Asian Earth Sci.,21(3):331-339.
Bai L,Zhang T Z.2015.Complex deformation pattern of the PamirHindu Kush region inferred from multi-scale double-differenceearthquake relocations.Tectonophysics,638:177-184,doi:10.1016/j.tecto.2014.11.006.
Bina C R,Helffrich G.1994.Phase transition Clapeyron slopes andtransition zone seismic discontinuity topography.J.Geophys.Res.,99(B8):15853-15860.
Castle J C,Creager K C.2000.Local sharpness and shear wavespeed jump across the 660km discontinuity.J.Geophys.Res.,105(B3):6191-6200.
Collier J D,Helffrich G R.1997.Topography of the“410”and“660”km seismic discontinuities in the Izu-Bonin SubductionZone.Geophys.Res.Lett.,24(12):1535-1538.
Collier J D,Helffrich G R,Wood B J.2001.Seismic discontinuitiesand subduction zones.Phys.Earth Planet.Inter.,127(1-4):35-49.
Deuss A.2009.Global observations of mantle discontinuities usingSS and PP precursors.Surv.Geophy.,30(4-5):301-326.
Dziewonski A M,Anderson D L.1981.Preliminary reference Earthmodel.Phys.Earth Planet.Inter.,25(4):297-356.
Engdahl E R,van der Hilst R,Buland R.1998.Global teleseismicearthquake relocation with improved travel times and proceduresfor depth determination.Bull.Seism.Soc.Am.,88(3):722-743.
Flanagan M P,Shearer P M.1998a.Global mapping of topographyon transition zone velocity discontinuities by stacking SSprecursors.J.Geophys.Res.,103(B2):2673-2692.
Flanagan M P,Shearer P M.1998b.Topography on the 410-kmseismic velocity discontinuity near subduction zones fromstacking of sS,sP,and pP precursors.J.Geophys.Res.,103(B9):21165-21182.
Fukao Y,Obayashi M.2013.Subducted slabs stagnant above,penetrating through,and trapped below the 660km discontinuity.J.Geophys.Res.,118(11):5920-5938.
Gudmundsson ó,Sambridge M.1998.A regionalized upper mantle(RUM)seismic model.J.Geophys.Res.,103(B4):7121-7136.
Jin Z M,Zhang Z J,Wu Y,et al.2013.Mantle transition zone andresearch methods.//Ding Z L ed.Research Methods in SolidEarth(in Chinese).Beijing:Science Publishing Company:402-434.
Kanasewich E R,Hemmings C D,Alpaslan T.1973.Nth-root stacknonlinear multichannel filter.Geophysics,38(2):327-338.
Kennett B L N,Engdahl E R.1991.Traveltimes for globalearthquake location and phase identification.Geophys.J.Int.,105(2):429-465.
Kennett B L N,Engdahl E R,Buland R.1995.Constraints onseismic velocities in the Earth from traveltimes.Geophys.J.Int.,122(1):108-124.
Koulakov I,Sobolev S V.2006.A tomographic image of Indianlithosphere break-off beneath the Pamir-Hindu Kush region.Geophys.J.Int.,164(2):425-440.
Li X,Sobolev S V,Kind R,et al.2000.A detailed receiverfunction image of the upper mantle discontinuities in the Japansubduction zone.Earth Planet.Sci.Lett.,183(3-4):527-541.
McFadden P L,Drummond B J,Karvis S.1986.The N-th rootstack:theory,application and examples.Geophysics,51(10):1879-1892.
Negredo A M,Replumaz A,Villaseor A,et al.2007.Modelingthe evolution of continental subduction processes in the PamirHindu Kush region.Earth Planet.Sci.Lett.,259(1-2):212-225.
Ning J Y,Zang S X.1990.The distribution of Earthquakes andStress State in Pamir-Hindu Kush Regions.Chinese J.Geophys.(in Chinese),33(6):657-669.
Obayashi M,Sugioka H,Yoshimitsu J,et al.2006.Hightemperature anomalies oceanward of subducting slabs at the410km discontinuity.Earth Planet.Sci.Lett.,243(1-2):149-158.
Pegler G,Das S.1998.An enhanced image of the Pamir-HinduKush seismic zone from relocated earthquake hypocentres.Geophys.J.Int.,134(2):573-595.
Revenaugh J,Jordan T H.1991.Mantle layering from ScSreverberations:1.Waveform inversion of zeroth-order reverberations.J.Geophys.Res.,96(B12):19749-19762.
Rost S,Thomas C.2002.Array seismology:methods andapplications.Rev.Geophys.,40(3):2-1—2-27,doi:10.1029/2000RG000100.
Sippl C,Schurr B,Yuan X,et al.2013.Geometry of the PamirHindu Kush intermediate-depth earthquake zone from localseismic data.J.Geophys.Res.,118(4):1438-1457.
Song T R A,Helmberger D V,Grand S P.2004.Low-velocity zoneatop the 410-km seismic discontinuity in the northwestern UnitedStates.Nature,427(6974):530-533.
Sun W B,He Y S,Chang Z,et al.2009.The plate subduction andstress state in the Pamir-Hindu Kush region.Seism.Geol.(inChinese),31(2):207-217.
Tian X B,Zhao D P,Zhang H S,et al.2010.Mantle transitionzone topography and structure beneath the central Tien Shanorogenic belt.J.Geophys.Res.,115(B10):B10308,doi:10.1029/2008JB006229.
Tian X B,Teng J W,Zhang H S,et al.2011.Structure of crustand upper mantle beneath the Ordos Block and the YinshanMountains revealed by receiver function analysis.Phys.EarthPlanet.Inter.,184(3-4):186-193.
Villaseor A,Spakman W,Engdahl E R.2003.Influence ofregional travel times in global tomographic models.EGS-AGUEUG Joint Assembly,Abstracts from the meeting held in Nice,France,6-11April 2003,abstract 8614.
Weidner D J,Wang Y B.2000.Phase transformations:implicationsfor mantle structure.//Karaoto S I,Forte A,Liebermann R,et al.,Earth′s Deep Interior:Mineral Physics and Tomographyfrom the Atomic to the Global Scale,Vol.GeophysicalMonograph Series 117.American Geophysical Union:215-235.
Zang S X,Zhou Y Z.2002.N-th root slant stack and its applicationin study of mantle discontinuities.Chinese J.Geophys.(in Chinese),45(3):407-415,doi:10.3321/j.issn:0001-5733.2002.03.012.
Zang S X,Zhou Y Z,Ning J Y,et al.2006.Multiple discontinuitiesnear 660km beneath Tonga area.Geophys.Res.Lett.,33(20):L20312,doi:10.1029/2006GL027262.
Zhang L P,Shao Z G,Li Z H.2014.Dynamic action of mutualsubduction between the Indian and the Eurasia plates in HinduKush-Pamir region.Chinese J.Geophys.(in Chinese),57(2):459-471,doi:10.6038/cjg20140212.
Zhang Z J,Yuan X H,Chen Y,et al.2010.Seismic signature ofthe collision between the east Tibetan escape flow and theSichuan Basin.Earth Planet.Sci.Lett.,292(3-4):254-264.
金振民,张忠杰,吴耀等.2013.地幔转换带和研究方法.//丁仲礼主编.固体地球科学研究方法.北京:科学出版社:402-434.
宁杰远,臧绍先.1990.帕米尔—兴都库什地区地震空间分布特征及应力场特征.地球物理学报,33(6):657-669.
孙文斌,和跃时,常征等.2009.帕米尔—兴都库什地区板块俯冲及其应力状态.地震地质,31(2):207-217.
臧绍先,周元泽.2002.N次根倾斜叠加在地幔间断面研究中的应用.地球物理学报,45(3):407-415,doi:10.3321/j.issn:0001-5733.2002.03.012.
张浪平,邵志刚,李志海.2014.印度板块与欧亚板块在兴都库什—帕米尔地区相互俯冲的动力作用分析.地球物理学报,57(2):459-471,doi:10.6038/cjg20140212.
Bai L,Zhang T Z.2015.Complex deformation pattern of the PamirHindu Kush region inferred from multi-scale double-differenceearthquake relocations.Tectonophysics,638:177-184,doi:10.1016/j.tecto.2014.11.006.
Bina C R,Helffrich G.1994.Phase transition Clapeyron slopes andtransition zone seismic discontinuity topography.J.Geophys.Res.,99(B8):15853-15860.
Castle J C,Creager K C.2000.Local sharpness and shear wavespeed jump across the 660km discontinuity.J.Geophys.Res.,105(B3):6191-6200.
Collier J D,Helffrich G R.1997.Topography of the“410”and“660”km seismic discontinuities in the Izu-Bonin SubductionZone.Geophys.Res.Lett.,24(12):1535-1538.
Collier J D,Helffrich G R,Wood B J.2001.Seismic discontinuitiesand subduction zones.Phys.Earth Planet.Inter.,127(1-4):35-49.
Deuss A.2009.Global observations of mantle discontinuities usingSS and PP precursors.Surv.Geophy.,30(4-5):301-326.
Dziewonski A M,Anderson D L.1981.Preliminary reference Earthmodel.Phys.Earth Planet.Inter.,25(4):297-356.
Engdahl E R,van der Hilst R,Buland R.1998.Global teleseismicearthquake relocation with improved travel times and proceduresfor depth determination.Bull.Seism.Soc.Am.,88(3):722-743.
Flanagan M P,Shearer P M.1998a.Global mapping of topographyon transition zone velocity discontinuities by stacking SSprecursors.J.Geophys.Res.,103(B2):2673-2692.
Flanagan M P,Shearer P M.1998b.Topography on the 410-kmseismic velocity discontinuity near subduction zones fromstacking of sS,sP,and pP precursors.J.Geophys.Res.,103(B9):21165-21182.
Fukao Y,Obayashi M.2013.Subducted slabs stagnant above,penetrating through,and trapped below the 660km discontinuity.J.Geophys.Res.,118(11):5920-5938.
Gudmundsson ó,Sambridge M.1998.A regionalized upper mantle(RUM)seismic model.J.Geophys.Res.,103(B4):7121-7136.
Jin Z M,Zhang Z J,Wu Y,et al.2013.Mantle transition zone andresearch methods.//Ding Z L ed.Research Methods in SolidEarth(in Chinese).Beijing:Science Publishing Company:402-434.
Kanasewich E R,Hemmings C D,Alpaslan T.1973.Nth-root stacknonlinear multichannel filter.Geophysics,38(2):327-338.
Kennett B L N,Engdahl E R.1991.Traveltimes for globalearthquake location and phase identification.Geophys.J.Int.,105(2):429-465.
Kennett B L N,Engdahl E R,Buland R.1995.Constraints onseismic velocities in the Earth from traveltimes.Geophys.J.Int.,122(1):108-124.
Koulakov I,Sobolev S V.2006.A tomographic image of Indianlithosphere break-off beneath the Pamir-Hindu Kush region.Geophys.J.Int.,164(2):425-440.
Li X,Sobolev S V,Kind R,et al.2000.A detailed receiverfunction image of the upper mantle discontinuities in the Japansubduction zone.Earth Planet.Sci.Lett.,183(3-4):527-541.
McFadden P L,Drummond B J,Karvis S.1986.The N-th rootstack:theory,application and examples.Geophysics,51(10):1879-1892.
Negredo A M,Replumaz A,Villaseor A,et al.2007.Modelingthe evolution of continental subduction processes in the PamirHindu Kush region.Earth Planet.Sci.Lett.,259(1-2):212-225.
Ning J Y,Zang S X.1990.The distribution of Earthquakes andStress State in Pamir-Hindu Kush Regions.Chinese J.Geophys.(in Chinese),33(6):657-669.
Obayashi M,Sugioka H,Yoshimitsu J,et al.2006.Hightemperature anomalies oceanward of subducting slabs at the410km discontinuity.Earth Planet.Sci.Lett.,243(1-2):149-158.
Pegler G,Das S.1998.An enhanced image of the Pamir-HinduKush seismic zone from relocated earthquake hypocentres.Geophys.J.Int.,134(2):573-595.
Revenaugh J,Jordan T H.1991.Mantle layering from ScSreverberations:1.Waveform inversion of zeroth-order reverberations.J.Geophys.Res.,96(B12):19749-19762.
Rost S,Thomas C.2002.Array seismology:methods andapplications.Rev.Geophys.,40(3):2-1—2-27,doi:10.1029/2000RG000100.
Sippl C,Schurr B,Yuan X,et al.2013.Geometry of the PamirHindu Kush intermediate-depth earthquake zone from localseismic data.J.Geophys.Res.,118(4):1438-1457.
Song T R A,Helmberger D V,Grand S P.2004.Low-velocity zoneatop the 410-km seismic discontinuity in the northwestern UnitedStates.Nature,427(6974):530-533.
Sun W B,He Y S,Chang Z,et al.2009.The plate subduction andstress state in the Pamir-Hindu Kush region.Seism.Geol.(inChinese),31(2):207-217.
Tian X B,Zhao D P,Zhang H S,et al.2010.Mantle transitionzone topography and structure beneath the central Tien Shanorogenic belt.J.Geophys.Res.,115(B10):B10308,doi:10.1029/2008JB006229.
Tian X B,Teng J W,Zhang H S,et al.2011.Structure of crustand upper mantle beneath the Ordos Block and the YinshanMountains revealed by receiver function analysis.Phys.EarthPlanet.Inter.,184(3-4):186-193.
Villaseor A,Spakman W,Engdahl E R.2003.Influence ofregional travel times in global tomographic models.EGS-AGUEUG Joint Assembly,Abstracts from the meeting held in Nice,France,6-11April 2003,abstract 8614.
Weidner D J,Wang Y B.2000.Phase transformations:implicationsfor mantle structure.//Karaoto S I,Forte A,Liebermann R,et al.,Earth′s Deep Interior:Mineral Physics and Tomographyfrom the Atomic to the Global Scale,Vol.GeophysicalMonograph Series 117.American Geophysical Union:215-235.
Zang S X,Zhou Y Z.2002.N-th root slant stack and its applicationin study of mantle discontinuities.Chinese J.Geophys.(in Chinese),45(3):407-415,doi:10.3321/j.issn:0001-5733.2002.03.012.
Zang S X,Zhou Y Z,Ning J Y,et al.2006.Multiple discontinuitiesnear 660km beneath Tonga area.Geophys.Res.Lett.,33(20):L20312,doi:10.1029/2006GL027262.
Zhang L P,Shao Z G,Li Z H.2014.Dynamic action of mutualsubduction between the Indian and the Eurasia plates in HinduKush-Pamir region.Chinese J.Geophys.(in Chinese),57(2):459-471,doi:10.6038/cjg20140212.
Zhang Z J,Yuan X H,Chen Y,et al.2010.Seismic signature ofthe collision between the east Tibetan escape flow and theSichuan Basin.Earth Planet.Sci.Lett.,292(3-4):254-264.
金振民,张忠杰,吴耀等.2013.地幔转换带和研究方法.//丁仲礼主编.固体地球科学研究方法.北京:科学出版社:402-434.
宁杰远,臧绍先.1990.帕米尔—兴都库什地区地震空间分布特征及应力场特征.地球物理学报,33(6):657-669.
孙文斌,和跃时,常征等.2009.帕米尔—兴都库什地区板块俯冲及其应力状态.地震地质,31(2):207-217.
臧绍先,周元泽.2002.N次根倾斜叠加在地幔间断面研究中的应用.地球物理学报,45(3):407-415,doi:10.3321/j.issn:0001-5733.2002.03.012.
张浪平,邵志刚,李志海.2014.印度板块与欧亚板块在兴都库什—帕米尔地区相互俯冲的动力作用分析.地球物理学报,57(2):459-471,doi:10.6038/cjg20140212.
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