鄂尔多斯地块东南缘地带Moho深度变化特征研究
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摘要
鄂尔多斯地块东南缘是主要的历史强震活跃区,曾经多次发生6级或以上的强烈地震,其边缘边界具有较强的地震活动性.本文利用该区域内分布的固定台站数据记录的大量远震体波波形资料,应用频率域反褶积方法提取远震P波接收函数,由H-κ方法测定了各台站下方的Moho深度和Vp/Vs值.研究结果表明:鄂尔多斯地块东南缘的Vp/Vs值介于1.6～1.9之间.东缘的Moho深度介于33.4～45km之间,太原断陷盆地附近的Moho深度较浅,最浅处为33.4km;东部北段的延怀盆地、蔚县盆地、阳原盆地和南段的临汾盆地附近Moho深度变化不大,平均深度为40km.而在东缘东侧,因存在着山西断陷带,导致块体边缘的Moho深度要小于块体内部的Moho深度.块体南缘的Moho深度介于31.0～53.1km之间,自东段向西段Moho深度逐渐变大,从渭河盆地附近的31.0km增厚至秦岭造山带地段的53.1km.总之,鄂尔多斯地块东南缘地带的Moho深度和Vp/Vs值分布具有明显的分块特征,块体内部结构比较稳定,东缘东段地壳结构相对一致,东缘东侧与西侧地壳深度具有明显的差异性,从山西断陷以东向西地壳厚度逐渐增厚,很好地对应了其地质构造特点.
The Ordos Block′s Southeastern Margin areas are a region of strong historical earthquakes where had happened a few strong earthquakes above magnitude 6.0,so these areas have strong seismicity.We selected broadband teleseismic waveform data recorded by the permanent stations spread over Ordos Block′s Southeastern Margin areas to get P wave receiver function using deconvolution in Frequency Domain,then the Moho depth and Vp/Vs ratio in the Ordos block′s Southeastern Margin Areas are estimated by teleseismic receiver function using H-κ method.Our study shows that the velocity ratio in this region is between 1.6 and 1.9,and the Moho depth beneath the Eastern areas is between 33.4~45 km.The lowest Moho depth of the areas lies in Taiyuan basin and it is about 33.4 km.Around Yanhuai basin,Weixian basin,Yangyuan basin and Linfen basin,the Moho depth is about 40 km.The Moho depth beneath the southern areas is between 31.0~53.1 km,and gradually increases from eastern areas to western areas.Therefore,the Moho depth and the velocity ratio show strong lateral variations with geological structure in the areas.
The Ordos Block′s Southeastern Margin areas are a region of strong historical earthquakes where had happened a few strong earthquakes above magnitude 6.0,so these areas have strong seismicity.We selected broadband teleseismic waveform data recorded by the permanent stations spread over Ordos Block′s Southeastern Margin areas to get P wave receiver function using deconvolution in Frequency Domain,then the Moho depth and Vp/Vs ratio in the Ordos block′s Southeastern Margin Areas are estimated by teleseismic receiver function using H-κ method.Our study shows that the velocity ratio in this region is between 1.6 and 1.9,and the Moho depth beneath the Eastern areas is between 33.4~45 km.The lowest Moho depth of the areas lies in Taiyuan basin and it is about 33.4 km.Around Yanhuai basin,Weixian basin,Yangyuan basin and Linfen basin,the Moho depth is about 40 km.The Moho depth beneath the southern areas is between 31.0~53.1 km,and gradually increases from eastern areas to western areas.Therefore,the Moho depth and the velocity ratio show strong lateral variations with geological structure in the areas.
引文
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[17]李永华,吴庆举,安张辉等.青藏高原东北缘地壳S波速度结构与泊松比及其意义,地球物理学报,2006,49(5):1359-1368.Li Y H,Wu Q J,An Z H,et al.The Poisson ratio andcrustal structure across the NE Tibetan Plateau determinedfrom receiver functions.Chinese J.Geophys.(in Chinese),2006,49(5):1359-1368.
[18]廖昌珍,张岳桥,温长顺.鄂尔多斯盆地东缘边界带构造样式及其区域构造意义,地质学报,2007:81(4):466-474.Liao C Z,Zhang Y Q,Wen C S.Structural styles of theEastern Boundary zone of the Ordos Basin and its regionaltectonic significance.Acta Geologica Sinica(in Chinese),2007,81(4):466-474.
[19]江为为,郝天珧,宋海斌.鄂尔多斯盆地地质地球物理场特征与地壳结构.地球物理学进展,2000,15(3):45-53.Jiang W W,Hao T Y,Song H B.Crustal structure andgeological and geophysical features of Ordos basin.Progressin Geophysics(in Chinese),2000,15(3):45-53.
[2]陆一锋,徐鸣洁,王良书等.相位加权叠加方法在探测鄂尔多斯东南缘地壳结构中的应用.高校地质学报,2011,17(4):562-568.Lu Y F,Xu M J,Wang L S,et al.An application of phase-weighted stacks to study the crustal structures in thesoutheastern margin of the Ordos block.Geological Journalof China Universities(in Chinese),2011,17(4):562-568.
[3]张学民,刁桂苓,束沛镒.鄂尔多斯块体及其东南缘剪切波速度结构与波速比研究.中国地震,2004,20(1):53-63.Zhang X M,Diao G L,Shu P Y.Study on shear wavevelocity structure and velocity ratio under the Ordos Plate andits southeastern marginal areas.Earthquake Research inChina(in Chinese),2004,20(1):53-63.
[4]任雪梅,高孟潭,冯静.鄂尔多斯地块周缘历史强震的影响烈度研究.中国地震,2010,26(4):450-456.Ren X M,Gao M T,Feng J.Study on historical strongearthquakes affected intensity of counties and cities in theErdos area.Earthquake Research in China(in Chinese),2010,26(4):450-456.
[5]Ducker K G,Sheehan A F.Mantle discontinuity structurefrom midpoint stacks of converted P to S waves across theYellow stone hotspot track.Journal Geophysical Research,1997,102(B4):8313-8327.
[6]Li A B,Fischer K M,Wysession M E,et al.Mantlediscontinuities and temperature under the North Americancontinental keel.Nature,1998,395(6698):160-163.
[7]Jones C H,Phinney R A.Seismic structure of the lithospherefrom teleseismic converted arrivals observed at small arrays inthe southern Sierra Nevada and vicinity,California.Journalof Geophysical Research,1998,103(B5):10065-10090.
[8]Kosarev G,Kind R,Sobolev S V,et al.Seismic evidence fora detached Indian lithospheric mantle beneath Tibet.Science,1999,283(5406):1306-1309.
[9]Zandt G,Myers S C,Wallace T C.Crust and mantlestructure across the Basin and Range-Colorado Plateauboundary at 37°N latitude and implications for Cenozoicextensional mechanism.Journal of Geophysical Research,1995,100(B6):10529-10548.
[10]Zandt G,Ammon C J.Continental crust compositionconstrained by measurements of crusta1 Poissson′s ratio.Nature,2002,374(6518):152-154.
[11]Owans T J,Zandt G,Taylor S R.Seismic evidence for anancient rift beneath the Cumberland plateau,Tennessee:Adetailed analysis of broadband teleseismic P waveforms.Journal of Geophysical Research,1984,89(B9):7783-7795.
[12]Zhu L P,Kanamori H.Moho depth variation in southernCalifornia from teleseismic receiver functions.Journal ofGeophysical Research,2000,105(B2):2969-2980.
[13]Li S L,Mooney W D,Fan J C.Crustal structure of mainlandChina from deep seismic sounding data.Tectonophysics,2006,420(1-2):239-252.
[14]陈九辉,刘启元,李顺成等.青藏高原东北缘——鄂尔多斯地块地壳上地幔S波速度结构.地球物理学报,2005,48(2):333-342.Chen J H,Liu Q Y,Li S C,et al.Crust and upper mantle S-wave velocity structure across Northeastern Tibetan P1ateauand Ordos block.Chinese J.Geophys.(in Chinese),2005,48(2):333-342.
[15]韩忠东,陈顒,杨锋杰等.鄂尔多斯地台南部边缘环形构造的GPS证据及深部地球动力学解释.中国西部科技,2008,7(3):1-5.Han Z D,Chen Y,Yang F J,et al.The GPS evidences anddepth earth dynamics explanations of the ring structure insouth Ordos platform.Science and Technology of WestChina(in Chinese),2008,7(3):1-5.
[16]杨锋杰,王明镇,李增学等.鄂尔多斯盆地南部环形影像特征及地质意义.地球科学与环境学报,2006,28(3):37-41.Yang F J,Wang M Z,Li Z X,et al.Ring structure in southOrdos Basin and its geologic genesis.Journal of EarthSciences and Environment,2006,28(3):37-41.
[17]李永华,吴庆举,安张辉等.青藏高原东北缘地壳S波速度结构与泊松比及其意义,地球物理学报,2006,49(5):1359-1368.Li Y H,Wu Q J,An Z H,et al.The Poisson ratio andcrustal structure across the NE Tibetan Plateau determinedfrom receiver functions.Chinese J.Geophys.(in Chinese),2006,49(5):1359-1368.
[18]廖昌珍,张岳桥,温长顺.鄂尔多斯盆地东缘边界带构造样式及其区域构造意义,地质学报,2007:81(4):466-474.Liao C Z,Zhang Y Q,Wen C S.Structural styles of theEastern Boundary zone of the Ordos Basin and its regionaltectonic significance.Acta Geologica Sinica(in Chinese),2007,81(4):466-474.
[19]江为为,郝天珧,宋海斌.鄂尔多斯盆地地质地球物理场特征与地壳结构.地球物理学进展,2000,15(3):45-53.Jiang W W,Hao T Y,Song H B.Crustal structure andgeological and geophysical features of Ordos basin.Progressin Geophysics(in Chinese),2000,15(3):45-53.
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