蒙古中南部地区面波相速度层析成像
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摘要
本文采用小波变换频时分析技术提取了1893条蒙古中南部地区双台间基阶Rayleigh波相速度频散曲线,通过对提取到的相速度频散进行二维反演,首次重构了蒙古高原中南部10~80s周期内分辨率为0.5°×0.5°的相速度分布图.结果表明,短周期相速度频散(10~20s)明显受地表地形控制,表现为杭爱—肯特山盆地为相对高速异常,而南部的戈壁带表现为相对低速异常;在30s到60s周期内,南部的戈壁带和北部的杭爱—肯特山盆地都显示出稳定的高速异常,而中部戈壁带则表现为低速异常.该低速异常区与新生代火山岩出露位置的一致性,暗示该低速异常可能与新生代火山活动有关.穿过蒙古高原中部的两条主要断裂带与研究区内的地震波速度分布具有很好的一致性,可能暗示两条断裂带一直延伸到整个岩石圈.此外,蒙古中南部地区的壳幔速度低于全球平均大陆值,且其相速度频散曲线与遭受破坏的克拉通,尤其大陆裂谷很相似,可能暗示着研究区具有薄的、活跃的岩石圈构造.
The Central Asian Orogenic Belt(CAOB)is one of the World′s largest Paleozoic orogeny zones,with more than 50% juvenile crust and provides a unique place to study the continental growth mechanism,as a matter of debate.Geological structure is influenced by the complicated orogeny.In order to study the structure of the crust and upper mantle in the middle of CAOB,we collected the vertical components of seismograms recorded at 69 broadband seismic stations deployed in the south-central Mongolia from August 2011 to August 2013.The fundamental mode Rayleigh-wave phase velocity dispersion along 1893inter-station paths in the central and southern Mongolia were estimated by the continuous wavelet transformation method.We selected 208 events with Mw between 5.5and 7.5,focal depths<70km,and epicentral distances between 15°and 100°.The vertical-component seismograms of these events were decimated to 1Hz and removed the average and linear trends.The dense distribution of seismic stations provided a good spatial and azimuthal coverage across the region.After determining the inter-station phase velocities,these dispersion data were utilized to construct the first 2-D phase velocity maps at 10~80swith 0.5°×0.5°horizontal resolution by applying a linear inversion strategy developed by Ditmar and Yanovskaya.The phase velocity distributions at shorter periods(10~20s)are controlled by geologic units on the surface.It shows that Hangay-Hentiy Basin is associated with high velocity anomaly and the Gobi desert in the south low velocity with 0.1~0.2km·s-1 difference.For shorter periods,the difference is larger.At 20~40s,phase velocities are strongly influenced by the velocity structure in the middle,lower crust and even upper mantle as well as by crustal thickness.According to the receiver function,the crustal thickness in the northwest is about46 km and is reduced to 38 km in the southeast.It is interesting that the northwest still shows high phase velocities.At 40~80s,the distributions in the Southern Gobi and Hangay-Hentiy Basin show high velocity while the Middle Gobi shows low velocity.All phase velocity dispersion curves from this study is averaged and then compared with dispersion in some typical regions.The phase velocity across the region is obviously lower than that of AK135 model.Compared to eastern North China Craton,the difference becomes less with period longer than 40 s.Our averaged dispersion curve is strikingly similar with that of the Western branch of the East African Rift.Based on the distributions of Cenozoic volcanic rock in the Middle Gobi,it is inferred that the low velocity anomaly is related to the Cenozoic volcanism.The locations of the two main faults in the middle Mongolia is consistent with the features of phase velocity distributions at almost all periods.This indicates that the depth of faults extends to entire lithosphere.In addition,the velocity in the crust and upper mantle is lower than AK135 and the dispersion shows the similar characteristic with that of destructed craton,especially the continental rift.It indicates that the lithosphere in the central and southern Mongolia is thin and active.
引文
Adams A,Nyblade A,Weeraratne D.2012.Upper mantle shearwave velocity structure beneath the East African plateau:evidence for a deep,plateauwide low velocity anomaly.GeophysicalJournal International,189(1):123-142,doi:10.1111/j.1365-246X.2012.05373.x.
    Badarch G,Cunningham W D,Windley B F.2002.A new terranesubdivision for Mongolia:implications for the Phanerozoiccrustal growth of Central Asia.Journal of Asian EarthSciences,21(1):87-110.
    Barruol G,Deschamps A,Déverchere J,et al.2008.Upper mantleflow beneath and around the Hangay dome,Central Mongolia.Earth and Planetary Science Letters,274(1-2):221-233,doi:10.1016/j.epsl.2008.07.027.
    Bayasgalan A,Jackson J,Ritz J F,et al.1999.Field examples ofstrike-slip fault terminations in Mongolia and their tectonicsignificance.Tectonics,18(3):394-411.
    Cunningham D.2005.Active intracontinental transpressionalmountain building in the Mongolian Altai:Defining a new classof orogen.Earth and Planetary Science Letters,240(2):436-444,doi:10.1016/j.epsl.2005.09.013.
    Cunningham W D,Windley B F,Dorjnamjaa D,et al.1996.Astructural transect across the Mongolian western Altai:activetranspressional mountain building in central Asia.Tectonics,15(1):142-156.
    Cunningham W D.2001.Cenozoic normal faulting and regionaldoming in the southern Hangay region,Central Mongolia:implications for the origin of the Baikal rift province.Tectonophysics,331(4):389-411.
    Ditmar P G,Yanovskaya T B.1987.A generalization of the BackusGilbert method for estimation of lateral variations of surfacewave velocity.Izv.Phys.Solid Earth,23:470-477.
    Gao S,Davis P M,Liu H,et al.1994.Seismic anisotropy andmantle flow beneath the Baikal rift zone.Nature,371(6493):149-151.
    Gao S S,Liu K H,Davis P M,et al.2003.Evidence for small-scalemantle convection in the upper mantle beneath the Baikal riftzone.Journal of Geophysical Research:Solid Earth,108(B4),doi:10.1029/2002JB002039.
    Gao S S,Liu K H,Chen C.2004.Significant crustal thinningbeneath the Baikal rift zone:New constraints from receiverfunctions analysis.Geophys.Res.Lett.,31(20):L20610,doi:10.1029/2004GL020813.
    He J,Wu Q J,Gao M T,et al.2014.Crustal structure and Poissonratio beneath the central and southern Mongolia derived fromreceiver functions.Chinese Journal Geophysics,57(7):2386-2394,doi:10.6038/cjg20140732.
    IAVCEI.1973.Post-Miocene Volcanoes of the World.IAVCEIData Sheets,Rome:International Association of Volcanologyand Chemistry of the Earth′s Interior.
    Khain V E.1990.Origin of the Central Asian mountain belt:collision or mantle diapirism.Journal of Geodynamics,11(4):389-394.
    Kiselev A I,Popov A M.1992.Asthenospheric diapir beneath theBaikal rift:petrological constraints.Tectonophysics,208(1):287-295.
    Koulakov I,Bushenkova N.2010.Upper mantle structure beneaththe Siberian craton and surrounding areas based on regionaltomographic inversion of P and PP travel times.Tectonophysics,486(1-4):81-100.
    Larson K M,Bürgmann R,Bilham R,et al.1999.Kinematics ofthe India-Eurasia collision zone from GPS measurements.Journal of Geophysical Research:Solid Earth(1978—2012),104(B1):1077-1093.
    Lebedev S,Meier T,van der Hilst R D.2006.Asthenospheric flowand origin of volcanism in the Baikal Rift area.Earth Planet.Sci.Lett.,249(3-4):415-424,doi:10.1016/j.epsl.2006.07.007.
    Li Y H,Wu Q J,Zhang R Q,et al.2009.The lithospheric thinningof the North China Craton inferred from Rayleigh wavesinversion.Geophysical Journal International,177(3):1334-1342.
    Li Y H,Wu Q J,Pan J T,et al.2013.An upper-mantle S-wavevelocity model for East Asia from Rayleigh wave tomography.Earth Planet.Sci.Lett.,377-378:367-377.
    Molnar P,Tapponnier P.1975.Cenozoic tectonics of Asia:effectsof a continental collision.Science,189(4201):419-426.
    Petit C,Koulakov I,Deverchère J.1998.Velocity structure aroundthe Baikal rift zone from teleseismic and local earthquake traveltimes and geodynamic implications.Tectonophysics,296(1-2):125-144.
    Petit C,Déverchère J,Calais E,et al.2002.Deep structure andmechanical behavior of the lithosphere in the Hangai-Hvsglregion,Mongolia:new constraints from gravity modeling.Earth and Planetary Science Letters,197(3-4):133-149.
    Petit C,Fournier M.2005.Present-day velocity and stress fields ofthe Amurian Plate from thin-shell finite-element modelling.Geophys.J.Int.,160(1):358-370.
    Ritzwoller M H,Levshin A L.1998.Eurasian surface wavetomography:Group velocities.Journal of Geophysical Research:Solid Earth(1978—2012),103(B3):4839-4878.
    Si S K,Tian X B,Zhang H S,et al.2012.Prevalent thickening andlocal thinning of the mantle transition zone beneath the Baikalrift zone and its dynamic implications.Science China:EarthSciences,42(11):1647-1659.
    Tapponnier P,Molnar P.1979.Active faulting and Cenozoictectonics of the Tien Shan,Mongolia,and Baykal regions.Journal of Geophysical Research:Solid Earth(1978—2012),84(B7):3425-3459.
    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.Physics ofthe Earth and Planetary Interiors,184(3-4):186-193.
    Tiberi C,Deschamps A,Déverchère J,et al.2008.Asthenosphericimprints on the lithosphere in Central Mongolia and SouthernSiberia from a joint inversion of gravity and seismology(MOBAL experiment).Geophys.J.Int.,175(3):1283-1297.
    Wang H Z,He G Q,Zhang S H.2006.The geology of China andMongolia.Earth Science Frontiers,13(6):1-13.
    Whitford-Stark J L.1987.A survey of Cenozoic volcanism onmainland Asia.Geol.Soc.Amer.Spec.Pap.,213:1-74.
    Windley B F,Allen M B.1993.Mongolian plateau:Evidence for alate Cenozoic mantle plume under central Asia.Geology,21(4):295-298.
    Wu Q J,Zhang X F,Pan J T,et al.2009.Measurement ofinterstation phase velocity by wavelet transformation.Earthq.Sci.,22(4):425-429.
    Yanovskaya T B,Ditmar P G.1990.Smoothness criteria in surfacewave tomography.Geophys.J.Int.,102(1):63-72.
    Yi G X,Yao H J,Zhu J S,et al.2008.Rayleigh-wave phasevelocity distribution in China continent and its adjacentregions.Chinese Journal Geophysics,51(2):402-411:
    Zhang J L,Tian X B,Zhang H S,et al.2012.The crust and uppermantle anisotropy in Baikal Rift Zone and its dynamicsignificance.Chinese Journal Geophysics,55(08):2523-2538,doi:10.6038/j.issn.0001-5733.2012.08.005.
    Zhao D P,Lei J S,Inoue T,et al.2006.Deep structure and originof the Baikal rift zone.Earth Planet.Sci.Lett.,243(3-4):681-691.
    Zorin Y A,Kozhevnikov V M,Novoselova M R,et al.1989.Thickness of the lithosphere beneath the Baikal rift zone andadjacent regions.Tectonophysics,168(4):327-337.
    Zorin Y A,Turutanov E K,Mordvinova V V,et al.2003.TheBaikal rift zone:the effect of mantle plumes on olderstructure.Tectonophysics,371(1-4):153-173,doi:10.1016/S0040-1951(03)00214-2.
    Zorin Y A,Turutanov E K,Kozhevnikov V M,et al.2006.Cenozoic upper mantle plumes in east Siberia and centralMongolia and subduction of the Pacific plate.Doklady EarthSciences,409(1):723-726.
    何静,吴庆举,高孟潭等.2014.利用接收函数方法研究蒙古中南部地区地壳结构.地球物理学报,57(7):2386-2394,doi:10.6038/cjg20140732.
    司少坤,田小波,张洪双等.2012.贝加尔裂谷区地幔过渡带大范围增厚与局部减薄现象及其动力学意义.中国科学D辑:地球科学,42(11):1647-1659.
    王鸿祯,何国琦,张世红.2006.中国与蒙古之地质.地学前缘,13(6):1-13.
    易桂喜,姚华建,朱介寿等.2008.中国大陆及邻区Rayleigh面波相速度分布特征.地球物理学报,51(2):402-411.
    张建利,田小波,张洪双等.2012.贝加尔裂谷区地壳上地幔复杂的各向异性及其动力学意义.地球物理学报,55(8):2523-2538,doi:10.6038/j.issn.0001-5733.2012.08.005.

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