天山—帕米尔结合带的地壳速度结构及地震活动研究
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摘要
利用流动地震台阵记录的地震数据,通过地震层析技术反演了天山—帕米尔结合带的P波速度结构,揭示出地壳结构的非均匀特征及其与地震活动的对应关系.分析结果表明,天山和西昆仑的双向挤压导致塔里木西部边缘地壳严重变形,在山前地区形成基底隆起带,地壳深部则被断裂分割成为若干块体,有的块体可能卷入造山带内部;喀什坳陷地壳深部结构相对完整,变形程度较弱;天山和西昆仑的地壳结构显示出缩短增厚的波速特性,在与塔里木接壤的局部地区,壳幔边界附近存在热物质的侵入迹象.大部分地震都发生在塔里木西部边缘的壳内高速块体周围,推测块体之间的相互作用和应力调整是导致天山—帕米尔结合带频繁发生地震的主要原因,伽师地震则与构造变形由天山向塔里木内部扩展以及该地区的地壳非均匀结构有关.
Using recording data from a temporary seismic network, we obtained P wave velocity structure of the Tianshan-Pamir conjunctive zone by tomographic inversion, revealing the heterogeneity of crustal structure and its relations to seismic activity. The results show that the collision between the Tianshan and Pamir caused strong crustal deformation on the western edge of the Tarim basin and resulted in basement uplift zones in the foreland areas. The deep crust is separated into several blocks by faults and some of them are wrapped within mountain belts. The deep crust of the Kashi depression has a relatively stable structure with less deformation, while the crust of the Tianshan and western Kunlun shows a velocity feature of shortening and thickening. Moreover, evidence of heating or hot perturbation can be observed near the crust-mantle boundary beneath the areas adjacent to the Tarim basin. Most earthquakes in this area are concentrated around high velocity blocks in the western end of the Tarim basin. We infer that the frequent earthquakes in the Tianshan-Pamir conjunctive zone can be attributed to the interaction and stress adjustment between these blocks, while the earthquakes in the Jiashi area is related to the penetration of tectonic activity from the Tianshan into the Tarim basin and the heterogeneous structure of the crust.
Using recording data from a temporary seismic network, we obtained P wave velocity structure of the Tianshan-Pamir conjunctive zone by tomographic inversion, revealing the heterogeneity of crustal structure and its relations to seismic activity. The results show that the collision between the Tianshan and Pamir caused strong crustal deformation on the western edge of the Tarim basin and resulted in basement uplift zones in the foreland areas. The deep crust is separated into several blocks by faults and some of them are wrapped within mountain belts. The deep crust of the Kashi depression has a relatively stable structure with less deformation, while the crust of the Tianshan and western Kunlun shows a velocity feature of shortening and thickening. Moreover, evidence of heating or hot perturbation can be observed near the crust-mantle boundary beneath the areas adjacent to the Tarim basin. Most earthquakes in this area are concentrated around high velocity blocks in the western end of the Tarim basin. We infer that the frequent earthquakes in the Tianshan-Pamir conjunctive zone can be attributed to the interaction and stress adjustment between these blocks, while the earthquakes in the Jiashi area is related to the penetration of tectonic activity from the Tianshan into the Tarim basin and the heterogeneous structure of the crust.
引文
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[2]ReigberCh,MichelGW,GalasR,etal.Newspacegeodetic constrainsonthedistributionofdeformationinCentralAsia.Earth Planet.Sci.Lett.,2001,191:157～165
[3]王琪,丁国瑜,乔学军等.用GPS研究南天山(伽师)地区现今地壳变形.地震学报,2000,22(3):263～270WangQ,DingGY,QiaoXJ,etal.Researchonpresentcrustal deformationinthesouthernTianshan(Jiashi),ChinabyGPS geodesy.ActaSeismologicaSinica(inChinese),2000,22(3):263～270
[4]陈杰,丁国瑜,BurbankDW等.中国西南天山山前的晚新生代构造与地震活动.中国地震,2001,17(2):134～155ChenJ,DingGY,BurbankDW,etal.LateCenozoictectonics andseismicityinthesouthwesternTianshan,China.Earthquake ResearchinChina(inChinese),2001,17(2):134～155
[5]沈军,汪一鹏,赵瑞斌等.帕米尔东北缘及塔里木盆地西北部弧形构造的扩展特征.地震地质,2001,23(3):381～389ShenJ,WangYP,ZhaoRB,etal.PropagationofCenozoic arcuatestructuresinnortheastPamirandnorthwestTarimbasin.SeismologyandGeology(inChinese),2001,23(3):381～389
[6]周仕勇,许忠淮,陈晓非.伽师强震群震源特征及震源机制力学成因分析.地球物理学报,2001,44(5):654～662ZhouSY,XuZH,ChenXF.Analysisonthesourcecharacteristics ofthe1997Jiashiswarm,westernChina.ChineseJ.Geophys.(in Chinese),2001,44(5):654～662
[7]李松林,张先康,MooneyWD等.伽师地震区地壳细结构及发震断层的初步研究.地球物理学报,2002,45(1):76～82LiSL,ZhangXK,MooneyWD,etal.Apreliminarystudyonfine structuresofJiashiearthquakeregionandearthquakegenerationfault.ChineseJ.Geophys.(inChinese),2002,45(1):76～82
[8]刘启元,陈九辉,李顺成等.新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨.地球物理学报,2000,43(3):356～365LiuQY,ChenJH,LiSC,etal.Passiveseismicexperimentin Xinjiang_Jiashistrongearthquakeregionanddiscussiononitsseismic genesis.ChineseJ.Geophys.(inChinese),2000,43(3):356～365
[9]张先康,赵金仁,张成科等.帕米尔东北侧地壳结构研究.地球物理学报,2002,45(5):665～671ZhangXK,ZhaoJR,ZhangCK,etal.Cruststructureatthe northeastsideofthePamirs.ChineseJ.Geophys.(inChinese),2002,45(5):665～671
[10]段永红,张先康,杨卓欣.帕米尔东北侧基底结构研究.地震学报,2002,24(4):378～384DuanYH,ZhangXK,YangZX.Studyonbasementstructuresof thenortheastPamirs.ActaSeismologicaSinica(inChinese),2002,24(4):378～384
[11]胥颐,刘福田,刘建华等.中国大陆西北造山带及其毗邻盆地的地震层析成像.中国科学(D辑),2000,30(2):113～122XuY,LiuFT,LiuJH,etal.Seismictomographybeneaththe orogenicbeltsandadjacentbasinsofnorthwesternChina.Sciencein China(SeriesD),2001,44(5):468～480
[12]雷建设,周蕙兰,赵大鹏.帕米尔及邻区地壳上地幔P波三维速度结构的研究.地球物理学报,2002,45(6):802～811LeiJS,ZhouHL,ZhaoDP.3DvelocitystructuresofPwavein thecrustanduppermantlebeneaththePamirandadjacentregion.ChineseJ.Geophys.(inChinese),2002,45(6):802～811
[13]胥颐,刘福田,刘建华等.天山地震带的地壳结构与强震构造环境.地球物理学报,2000,43(2):184～193XuY,LiuFT,LiuJH,etal.Crustalstructureandtectonic environmentofstrongearthquakesintheTianshanearthquakebelt.ChineseJ.Geophys.(inChinese),2000,43(2):184～193
[14]KennettBLN,EngdahlER.Traveltimesforglobalearthquake locationandphaseidentification.Geophy.J.Int.,1991,105(2):429～465
[15]刘福田,李强,吴华等.用于速度图像重建的层析成像法.地球物理学报,1989,32(1):46～61LiuFT,LiQ,WuH,etal.Onthetomographicinversemethod usedinvelocityimagereconstruction.ChineseJ.Geophys.(in Chinese),1989,32(1):46～61
[16]BurtmanVS,MolnarP.Geologicalandgeophysicalevidencefor deepsubductionofcontinentalcrustbeneaththePamir.Geological SocietyofAmerica,Boulder,Colorado,1993
[17]YinA,NieS,CraigP,etal.LateCenozoictectonicevolutionofthe southernTienShan.Tectonics,1998,17(1):1～27
[18]梅世蓉.地震前兆场物理模式与前兆时空分布机制研究(Ⅰ)-坚固体孕震模式的由来与证据.地震学报,1995,17(3):273～282MeiSR.Onthephysicalmodelofearthquakeprecursorfieldsand themechanismofprecursor’stimeandspacedistribution(Ⅰ)—originandevidencesofthestrongbodyearthquake_generatingmodel.ActaSeismologicaSinica,1995,8(3):337～349
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