新疆塔里木西昆仑宽频地震观测实验研究
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摘要
利用获取的宽频地震数据 ,采用接收函数方法 ,获得了塔里木块体与青藏高原北缘西昆仑山结合部位的地壳及上地幔结构新信息。塔里木块体的地壳结构相对简单 ,其块体南缘的莫霍界面深度为 4 2km ,且向南倾斜 ,在西昆仑山前深度增加到 5 0km左右。接收函数图象清晰地显示出 ,塔里木块体南缘和西昆仑山下存在南倾和北倾的构造特征 ,这些构造特征可以用地壳和上地幔相互穿插和变形的岩石圈碰撞模型来解释。
A broadband seismic deployment in 1998～1999 in southwestern Tarim provided data for imaging the crust and upper mantle across the contact zone between the Tarim block and the Tibetan plateau. The Tarim basin is located to the north of Tibet and seems to be a seismic block in Northwest China. It is surrounded by two large mountain systems, namely the Tianshan Mountains and the Kunlun Mountains on the north and the south respectively, where high seismicity is observed. Although its flat platform and seismic characteristics are recognized, how the Tarim block deforms internally and interacts with its neighboring areas remain unclear. In mid I997, the Institute of Geology, Chinese Academy of Geological Sciences and the Institute of Earth Sciences, Academia Sinica, initiated a corporate effort to study the seismotectonics of the Tarim basin. In particular, the project was focused on the transition between Tarim and Tibet, namely, the Kulunshan foreland. The full scale experiment began in mid 1998 with the emphasis placed on southern Tarim. A total of 12 broadband stations were set up along the border between the Tarim basin and the Kunlun Mountains covering an area of 350 km by 150 km. All stations were equipped with high resolution REFTEK 72 digital recorders and very broadband STS 2 sensors. Continuous recording data at 50 samples per second were stored in large capacity hard disks and were retrieved. The field operation ended in mid September, 1999. In total, the authors collected more than 200 teleseismic events. The crust under Tarim basin is relatively simple. The Moho discontinuity was mapped at a depth of 42 km near the northern end of the array, which dips gently southward to some 50 km beneath the Kunlun foreland. The Tarim basin appears to be rigid, with little shortening. Further southward, the imaging reveals a complex of reflectors in the lower crust and the upper mantle. There are both north and south dipping upper mantle structures under the Kunlun foreland and Kunlun Mountains region. It is found that the observations are quite consistent with a model of lithosphere collision in which the crust and the upper mantle on both sides interpenetrate and deform each other.
A broadband seismic deployment in 1998～1999 in southwestern Tarim provided data for imaging the crust and upper mantle across the contact zone between the Tarim block and the Tibetan plateau. The Tarim basin is located to the north of Tibet and seems to be a seismic block in Northwest China. It is surrounded by two large mountain systems, namely the Tianshan Mountains and the Kunlun Mountains on the north and the south respectively, where high seismicity is observed. Although its flat platform and seismic characteristics are recognized, how the Tarim block deforms internally and interacts with its neighboring areas remain unclear. In mid I997, the Institute of Geology, Chinese Academy of Geological Sciences and the Institute of Earth Sciences, Academia Sinica, initiated a corporate effort to study the seismotectonics of the Tarim basin. In particular, the project was focused on the transition between Tarim and Tibet, namely, the Kulunshan foreland. The full scale experiment began in mid 1998 with the emphasis placed on southern Tarim. A total of 12 broadband stations were set up along the border between the Tarim basin and the Kunlun Mountains covering an area of 350 km by 150 km. All stations were equipped with high resolution REFTEK 72 digital recorders and very broadband STS 2 sensors. Continuous recording data at 50 samples per second were stored in large capacity hard disks and were retrieved. The field operation ended in mid September, 1999. In total, the authors collected more than 200 teleseismic events. The crust under Tarim basin is relatively simple. The Moho discontinuity was mapped at a depth of 42 km near the northern end of the array, which dips gently southward to some 50 km beneath the Kunlun foreland. The Tarim basin appears to be rigid, with little shortening. Further southward, the imaging reveals a complex of reflectors in the lower crust and the upper mantle. There are both north and south dipping upper mantle structures under the Kunlun foreland and Kunlun Mountains region. It is found that the observations are quite consistent with a model of lithosphere collision in which the crust and the upper mantle on both sides interpenetrate and deform each other.
引文
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ZhaoWLandYuenDA .1987.InjectionofIndiancrustintoTibetanlowercrust:Atemperature dependentviscousmodel.Tectonics,(6):505～514.
KaoH ,RGao,RJRau,YGuan,RYChen,DNShi,WPChenandFTWu.1999.SeismologicalevidenceagainstthesubductionofTarimbe neathTibet.新疆地学海峡两岸学术讨论会论文集
吴功建,高锐等.1991.青藏高原“亚东格尔木地学断面”综合地球物理调查与研究.地球物理学报,34(5):552～562.
ChenRY ,RKao,HKao,LLi,RJRauandYGuan.1998.Broad bandseismicexperimentinTarimBasin:Resultsofreconnaissancedeploymentin1997.EOS ,Trans.AGU ,79.W 77.GaoRui,HuangDongding,LuDeyuan,QianGuihua,LiYingkang,KuangChaoyang,LiQiusheng,LiPengwu,FengRujin,GuanYe.2000.Deepseismicreflectionprofileacrosstheneturezonebe tweentheTarimbasinandtheWestKunlunMountains.ChineseSciencesBulletin,45:2281～2286.
KosarevG ,KingR ,SobolevSV ,YuanX ,HankaWandOreshinS .1999.SeismicevidenceforadetachedIndialithospheremantlebe neathTibet.Science.283:1306～1309.
LiQiusheng,GaoRui,LuDeyuanetal..2001.AnexplosiveseismicsoundingprofileacrossthetransitionzonebetweenwestKunlunMountainandTarimbasin.ScinceinChina(SeriesD),44(7):666～672.
LiuXun,WuShaozuetal..1997.TectonicEvolutionaroundtheTari ambasinonthesedimentaryfeatures.¨Ur櫣mqi:XinjiangSciencePress(inChinese).LayonCaenHandPMolnar.1984.GravityanomaliesandthestructureofwesternTibetandthesouthernTarimbasin.Geophys.Res.Lett.,(11):1251～1254.
MattePh,PTapponnier,NArnaud,LBourjoy,JPAvouac,PVidal,QLiu,YPanandYWang.1996.TectonicsofWesternTibet,betweentheTarimandtheIndus.EarthPlanet.Sci.Lett.,(142):311～330.
olnarP ,andP .Taponnier.1975.CenozoictectonicsofAsia:effectsofacontinentalcollision.Science,(189):419～426.NiJandJEYork,1978.LateCenozonictectonicsoftheTibetanplateau.J.Geophys.Res.,83:5377～5384.
WuGongjian,GaoRuietal..1991.ThemultidisciplinarystudiesalongYadondGolmudgeosciencetransectonQinghaiTibetplateau;Ac taGeophysicasinica.34(5):552～562(inChinese).
XiaoXuchang,LiuXun,GaoRuietal..2001.CollisionTectonicstheTarimblock(basin)andNorthwesternTibetplateau:NewObser vationsfromaMultidisciplinaryGeoscientificInvestigationintheWesternKunlunMountains.ActaGeologicalSinica,75(2):126～132.
ZhaoWLandYuenDA .1987.InjectionofIndiancrustintoTibetanlowercrust:Atemperature dependentviscousmodel.Tectonics,(6):505～514.
KaoH ,RGao,RJRau,YGuan,RYChen,DNShi,WPChenandFTWu.1999.SeismologicalevidenceagainstthesubductionofTarimbe neathTibet.新疆地学海峡两岸学术讨论会论文集
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