洱源-江川宽角地震剖面的地壳反射特征
摘要
通过对洱源-江川宽角反射地震资料的叠前偏移处理成像,得到了一个类似于近垂直入射多道地震数据的记录剖面.反射剖面图像与地壳速度结构共同揭示出地壳厚度由剖面西北端(约45km)向东南端(约40km)减薄.在洱源-楚雄西北附近深度约10km处存在一组向东南倾斜的强反射震相,其东南约50km处存在向西北倾斜的强反射震相.易门断裂两侧地壳反射属性具有明显的差异,易门断裂之西北方向深度25～40km处,中下地壳内存在两组强振幅,向东南方向上倾的地震反射同相轴,并被楚雄-建水断裂后期所错断,易门断裂之东南方向上,地壳内反射较为均一,未见特别明显的强间断面反射信息,这个反射结构被解释为印度板块东向俯冲与藏东缘地壳物质东向逃逸综合作用导致下地壳增厚和厚地壳变形的结果.
By prestack migration processing to the wide angle reflection seismic data of the Eryuan-Jiangchuan profile in Yunnan Province,we obtain a crustal reflectivity section which is similar to nearly-vertical incidence seismic data. Both the reflectivity image and the crustal velocity structure jointly demonstrate that the crustal thickness thins from about 45 km on the northwestern end of the profile to about 40 km on the southeastern end. Near the northwest of Eryuan and Chuxiong, there are a series of southeast-dipping strong reflectors at depth 10 km and a series of northwest-dipping strong reflection 50 km to its southwest. Crustal reflection attributes obviously differ on the both sides of the Yimen fault. To the northwest of the Yimen fault, two sets of reflectors with strong amplitude dipping upwards lie in the middle-lower crust of depths 25～40 km, and are cut by the Chuxiong-Jianshui fault. To the southeast of Yimen fault, no obvious strong discontinuous reflection appears in the crust. This unique crustal velocity structure and reflectivity images are explained to be the results of thickening and deformation of crust under the joint action of Indian plate's eastward subduction and eastward escape of the crustal material at the eastern margin of Tibet.
By prestack migration processing to the wide angle reflection seismic data of the Eryuan-Jiangchuan profile in Yunnan Province,we obtain a crustal reflectivity section which is similar to nearly-vertical incidence seismic data. Both the reflectivity image and the crustal velocity structure jointly demonstrate that the crustal thickness thins from about 45 km on the northwestern end of the profile to about 40 km on the southeastern end. Near the northwest of Eryuan and Chuxiong, there are a series of southeast-dipping strong reflectors at depth 10 km and a series of northwest-dipping strong reflection 50 km to its southwest. Crustal reflection attributes obviously differ on the both sides of the Yimen fault. To the northwest of the Yimen fault, two sets of reflectors with strong amplitude dipping upwards lie in the middle-lower crust of depths 25～40 km, and are cut by the Chuxiong-Jianshui fault. To the southeast of Yimen fault, no obvious strong discontinuous reflection appears in the crust. This unique crustal velocity structure and reflectivity images are explained to be the results of thickening and deformation of crust under the joint action of Indian plate's eastward subduction and eastward escape of the crustal material at the eastern margin of Tibet.
引文
[1]Zhang ZJ,Badal J,Li Y K.Crust-upper mantle seismic wave velocity structure across Southerneastern China.Tectonophysics,2005,395:137～157
[2]Zhang ZJ,Simon L,Klemperer.West-east variation in crustal thicknessin northern Lhasa block,central Tibet,fromdeep seismic sounding data.J.Geophys.Res.,2005,110(B9),B090403
[3]吴庆举,曾融生,赵文津.喜马拉雅-青藏高原的上地幔倾斜构造与陆-陆碰撞过程.中国科学(D辑),2004,34(10):919～925Wu QJ,Zeng R S,Zhao WJ.The slant upper mantle structure fromHimalayato Tibetan plateauanditsimplicationtothe continental collision process.Science in China(Series D)(in Chinese),2004,34(10):919～925
[4]滕吉文,王绍舟,姚振兴等.青藏高原及其邻近地区的地球物理场特征与大陆板块构造.地球物理学报,1980,23(3):254～268Teng J W,Wang S Z,Yao Z X,et al.Characteristics of the geophysical fields and plate tectonics of the Qinghai-Xizang plateau andits neighbouring regions.Chinese J.Geophys.(in Chinese),1980,23(3):254～268
[5]Milkereit B,Epili D,Green A G,et al.Migration of wide-angle seismic reflection data fromthe Grenville Front in Lake Huron.J.Geophys.Res.,1990,95:10987～10998
[6]Lafond C F,Levander A.Migrationof wide-aperture onshore-offshore seismic data,California:Seismic images of late stage subduction.J.Geophys.Res.,1995,100:22231～22243
[7]Zelt B C,Talwani M,Zelt C A.Prestack depth migration of dense wide-angle seismic data.Tectonophysics,1998,286:193～208
[8]Funck T,Louden K E.Wide-angle seismic transect across the Torngat Orogen northern Labrador:Evidence for a Proterozoic crustal root.J.Geophys.Res.,1999,104:7463～7480
[9]Pilipenko VN,Pavlenkova N I,Luosto U.Wide-angle reflection migration technique with an example from the POLAR profile(northern Scandinavia).Tectonophysics,1999,308:445～457
[10]Zhang ZJ,Wang GJ,TengJ W,Sinmon Klemperer.CDP mapping to obtainthe fine structure of the crust and upper mantle fromseismic sounding data:an example for the southeastern China.Physics ofthe Earth and PlanetaryInteriors,2000,122(1-2):133～146
[11]Qin YL,Zhang Z J,Li S L.CDP mapping in tilted transversely isotropic(TTI)media.PartⅠ:Method and effectiveness.Geophysical Prospecting,2003,51(4):315～324
[12]张中杰,秦义龙,陈■等.由宽角反射地震资料重建壳幔反射结构的相似性剖面.地球物理学报,2004,47(3):469～474Zhang ZJ,Qin Y L,Chen Y,et al.Reconstruction of the semblance section for the crust and mantle reflection structure by wide-angle reflection seismic data.Chinese J.Geophys.(in Chinese),2004,47(3):469～474
[13]胡鸿翔,陆涵行,王椿镛等.滇西地区地壳结构的爆破地震研究.地球物理学报,1986,29(2):133～143Hu HX,Lu HX,Wang C Y,et al.Astudy on crustal structure
[2]Zhang ZJ,Simon L,Klemperer.West-east variation in crustal thicknessin northern Lhasa block,central Tibet,fromdeep seismic sounding data.J.Geophys.Res.,2005,110(B9),B090403
[3]吴庆举,曾融生,赵文津.喜马拉雅-青藏高原的上地幔倾斜构造与陆-陆碰撞过程.中国科学(D辑),2004,34(10):919～925Wu QJ,Zeng R S,Zhao WJ.The slant upper mantle structure fromHimalayato Tibetan plateauanditsimplicationtothe continental collision process.Science in China(Series D)(in Chinese),2004,34(10):919～925
[4]滕吉文,王绍舟,姚振兴等.青藏高原及其邻近地区的地球物理场特征与大陆板块构造.地球物理学报,1980,23(3):254～268Teng J W,Wang S Z,Yao Z X,et al.Characteristics of the geophysical fields and plate tectonics of the Qinghai-Xizang plateau andits neighbouring regions.Chinese J.Geophys.(in Chinese),1980,23(3):254～268
[5]Milkereit B,Epili D,Green A G,et al.Migration of wide-angle seismic reflection data fromthe Grenville Front in Lake Huron.J.Geophys.Res.,1990,95:10987～10998
[6]Lafond C F,Levander A.Migrationof wide-aperture onshore-offshore seismic data,California:Seismic images of late stage subduction.J.Geophys.Res.,1995,100:22231～22243
[7]Zelt B C,Talwani M,Zelt C A.Prestack depth migration of dense wide-angle seismic data.Tectonophysics,1998,286:193～208
[8]Funck T,Louden K E.Wide-angle seismic transect across the Torngat Orogen northern Labrador:Evidence for a Proterozoic crustal root.J.Geophys.Res.,1999,104:7463～7480
[9]Pilipenko VN,Pavlenkova N I,Luosto U.Wide-angle reflection migration technique with an example from the POLAR profile(northern Scandinavia).Tectonophysics,1999,308:445～457
[10]Zhang ZJ,Wang GJ,TengJ W,Sinmon Klemperer.CDP mapping to obtainthe fine structure of the crust and upper mantle fromseismic sounding data:an example for the southeastern China.Physics ofthe Earth and PlanetaryInteriors,2000,122(1-2):133～146
[11]Qin YL,Zhang Z J,Li S L.CDP mapping in tilted transversely isotropic(TTI)media.PartⅠ:Method and effectiveness.Geophysical Prospecting,2003,51(4):315～324
[12]张中杰,秦义龙,陈■等.由宽角反射地震资料重建壳幔反射结构的相似性剖面.地球物理学报,2004,47(3):469～474Zhang ZJ,Qin Y L,Chen Y,et al.Reconstruction of the semblance section for the crust and mantle reflection structure by wide-angle reflection seismic data.Chinese J.Geophys.(in Chinese),2004,47(3):469～474
[13]胡鸿翔,陆涵行,王椿镛等.滇西地区地壳结构的爆破地震研究.地球物理学报,1986,29(2):133～143Hu HX,Lu HX,Wang C Y,et al.Astudy on crustal structure
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心