藏北地壳东西向结构与“下凹”莫霍面——来自宽角反射剖面的启示
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摘要
根据藏北色林错-雅安多510余公里长地震剖面上纵横波特征所识别的来自于莫霍反射及壳内反射震相,通过正演拟合解释了该纵剖面地壳纵横波速度与Poisson比结构.研究结果显示,雅鲁藏布江与班公湖-怒江两条缝合带之间地壳结构东西向变化剧烈,岩石圈结构在剖面中部厚度最深,达到80余公里;莫霍面东西向变化呈现“下凹”特征,自莫霍面“下凹”处沿剖面东西方向呈阶梯状抬升,且西向抬升速度较东向大;地壳内纵横波速度纵向（深度域）与横向（东西方向）均存在非均一性现象,且上地壳内27～34km深度处存在厚度约5～7km的低速层.上地壳内,剖面中段介质的Poisson比较剖面东段与剖面西段的低;下地壳内,剖面东段的Poisson比较剖面西段的Poisson比低.上地壳内介质的刚性变化特征不同于下地壳内介质的刚性变化特征,剖面东段下地壳内物质较剖面西段的刚度小,并蕴含着藏北地区下地壳物质伴随欧亚与印度板块碰撞而东向流动.藏北地区地壳结构东西向变化趋势与莫霍面“下凹”特征可能源于多期构造作用的叠加效应.
引文
1潘裕生.青藏高原第五缝合带的发现.地球物理学报,1994,37（2）:184～192
2潘裕生,文世宣,邓万明.岩石圈的形成与演化.见:孙鸿烈编.青藏高原的形成演化.上海:上海科学技术出版社,1996.10～99
3吴功建,肖序常,李廷栋.青藏高原亚东-格尔木地学断面.地质学报,1989,63（4）:285～296
4曾融生,朱介寿,周 兵.青藏高原及其东部邻区的三维地震波速度结构与大陆碰撞模型.地震学报,1992,14（增刊）:527～533
5朱志文,滕吉文.冈瓦纳大陆解体后印度板块分块北移并与欧亚板块碰撞的古地磁证据,中法喜马拉雅考察成果（1980）.北京:地质出版社,1984.17～23
6朱志文.西藏高原古地磁及大陆漂移.地球物理学报,1982,24（1）:40～49
7滕吉文,尹周勋,熊绍柏.西藏高原北部地区色林错-蓬错-那曲-索县地带地壳结构与速度分布.地球物理学报,1985,28（增刊Ⅰ）:28～42
8滕吉文.西藏高原地区地壳与土地幔地球物理研究概论.地球物理学报,1985,28（增刊Ⅰ）:1～15
9滕吉文,张中杰,王光杰,等.喜马拉雅碰撞造山带的深层动力过程与陆-陆碰撞新模型.地球物理学报,1999,42（4）:481～494
10滕吉文,张中杰,白武明,等.岩石圈物理学.北京:科学出版社,2000
11熊绍柏,滕吉文,尹周勋.西藏高原地区地壳厚度和莫霍界面的起伏.地球物理学报,1985,28（增刊Ⅰ）:16～27
12孔祥儒,王谦身,熊绍柏.西藏高原西部地球物理与岩石圈结构研究.中国科学,D辑,1996,26（4）:308～315
13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）:113～122
14杨 华.青藏高原航磁图展示的地球物理特征及地质构造意义.地球物理学报,1985,28（增刊Ⅰ）:185～195
15崔作舟,尹周勋,高恩源.等.青藏高原速度结构和深部构造.北京:地质出版社,1992
16崔军文,武长得,朱红,等.喜马拉雅碰撞带陆壳增厚与隆升机制.中国地质科学院院报,1990,21:55～64
17黄立言,卢德源,李小鹏,等.藏北色林湖-蓬错-雅安多地带的深部地震测深.见:李光岑,编.西藏地球物理文集.北京:地质出版社,1990.25～37
18 鄢家全,时振梁,汪素云,等.青藏高原的现代构造.地球物理学报,1981,24（4）:385～392
19 姚 虹,孙克忠,滕吉文,等.利用PS反射波研究西藏雅鲁藏布江北侧局部地区深部地壳结构.西北地震学报,1982,4（4）:57～62
20 张玉泉,谢应雯,李献华,等.青藏高原东部钾玄岩系岩浆岩同位素特征:岩石成因及其构造意义.中国科学,D辑,2000,30（5）:493～498
21 Chang Chengfa, Shackleton R M, Dewey J F, et al. The Geological Evolution of Tibet. London: The Royal Society, 1988
22 Cogan M, Nelson K D, Kidd W, et al. Shallow structure of the Yadong-Gulu rift, southern Tibet, from refraction analysis of INDEPTH CMP data. Tectonics, 1998, 17(1): 46-61
23 Hirn A, Xu Z, Teng J, et al. Lhasa block and ordering suture: a continuation of a 500 km Moho traverse through Tibet. Nature, 1984,307(5946): 25-27
24 Hirn A, Xu Z, Teng J. Crustal structure and variability of the Himalayan border of Tibet. Nature, 1984, 307(5946): 23-25
25 Him A, Sapin M, Lepine J C, et al. Increase in melt traction along south-north traverse below the Tibetan Plateau: Evidence from seismology. Tectonophysics, 1997, 273: 17 - 30
26 Makovsky Y, Klemperer S L, Ratschbacher L, et al. INDEPTH wide-angle reflection observation of P-wave to S-wave conversion from crustal bright spots in Tibet. Science, 1996, 274(5293): 1690 - 1691
27 Makovsky Y, Klemperer S L. Measuring the seismic properties of Tibetan bright spots: Evidence for free aqueous fluids in the Tibetan middle crust. Journal of Geophysical Research, 1999, 104(135): 10795 - 10825
28 Kind R, Ni J, Zhao W, et al. Evidence from earthquake data for a partially molten crustal layer in southern Tibet. Science, 1996, 274(5293): 1692- 1694
29 Stern T A, McBride J H. Seismic exploration of continental strike-slip zones. Tectonophysics, 1998, 286: 63 - 78
30 Teng J, Xiong S. Explosion seismological study for velocity distribution and structure of the crust and upper mantle from Damxung to Yadong of the Xizang Plateau. In: Proceedings of Symposium on Qinghai-Xizang(Tibet) Plateau (Beijing, China) Geological and Ecological Studies of Qinghai-Xizang Plateau. Beijing: Science Press, 1981. 691 - 710
31 Zeng R, Ding Z, Wu Q. A review of lithospheric structures in the Tibetan Plateau and constraints for dynamics. Pure App Geoph, 1995, 145(3-4): 425-443
32 Zhao W, Nelson K D, Project INDEPTH Team. Deep seismic reflection evidence for continental underthrusting beneath southern Tibet. Nature, 1993, 366: 557 - 559
33 Zhao W, Mechie J, Guo J, et al. Seismic mapping of crustal structures beneath the Indus-Yarlung suture, Tibet. Terra Nova, 1997,9:42-46
2潘裕生,文世宣,邓万明.岩石圈的形成与演化.见:孙鸿烈编.青藏高原的形成演化.上海:上海科学技术出版社,1996.10～99
3吴功建,肖序常,李廷栋.青藏高原亚东-格尔木地学断面.地质学报,1989,63（4）:285～296
4曾融生,朱介寿,周 兵.青藏高原及其东部邻区的三维地震波速度结构与大陆碰撞模型.地震学报,1992,14（增刊）:527～533
5朱志文,滕吉文.冈瓦纳大陆解体后印度板块分块北移并与欧亚板块碰撞的古地磁证据,中法喜马拉雅考察成果（1980）.北京:地质出版社,1984.17～23
6朱志文.西藏高原古地磁及大陆漂移.地球物理学报,1982,24（1）:40～49
7滕吉文,尹周勋,熊绍柏.西藏高原北部地区色林错-蓬错-那曲-索县地带地壳结构与速度分布.地球物理学报,1985,28（增刊Ⅰ）:28～42
8滕吉文.西藏高原地区地壳与土地幔地球物理研究概论.地球物理学报,1985,28（增刊Ⅰ）:1～15
9滕吉文,张中杰,王光杰,等.喜马拉雅碰撞造山带的深层动力过程与陆-陆碰撞新模型.地球物理学报,1999,42（4）:481～494
10滕吉文,张中杰,白武明,等.岩石圈物理学.北京:科学出版社,2000
11熊绍柏,滕吉文,尹周勋.西藏高原地区地壳厚度和莫霍界面的起伏.地球物理学报,1985,28（增刊Ⅰ）:16～27
12孔祥儒,王谦身,熊绍柏.西藏高原西部地球物理与岩石圈结构研究.中国科学,D辑,1996,26（4）:308～315
13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）:113～122
14杨 华.青藏高原航磁图展示的地球物理特征及地质构造意义.地球物理学报,1985,28（增刊Ⅰ）:185～195
15崔作舟,尹周勋,高恩源.等.青藏高原速度结构和深部构造.北京:地质出版社,1992
16崔军文,武长得,朱红,等.喜马拉雅碰撞带陆壳增厚与隆升机制.中国地质科学院院报,1990,21:55～64
17黄立言,卢德源,李小鹏,等.藏北色林湖-蓬错-雅安多地带的深部地震测深.见:李光岑,编.西藏地球物理文集.北京:地质出版社,1990.25～37
18 鄢家全,时振梁,汪素云,等.青藏高原的现代构造.地球物理学报,1981,24（4）:385～392
19 姚 虹,孙克忠,滕吉文,等.利用PS反射波研究西藏雅鲁藏布江北侧局部地区深部地壳结构.西北地震学报,1982,4（4）:57～62
20 张玉泉,谢应雯,李献华,等.青藏高原东部钾玄岩系岩浆岩同位素特征:岩石成因及其构造意义.中国科学,D辑,2000,30（5）:493～498
21 Chang Chengfa, Shackleton R M, Dewey J F, et al. The Geological Evolution of Tibet. London: The Royal Society, 1988
22 Cogan M, Nelson K D, Kidd W, et al. Shallow structure of the Yadong-Gulu rift, southern Tibet, from refraction analysis of INDEPTH CMP data. Tectonics, 1998, 17(1): 46-61
23 Hirn A, Xu Z, Teng J, et al. Lhasa block and ordering suture: a continuation of a 500 km Moho traverse through Tibet. Nature, 1984,307(5946): 25-27
24 Hirn A, Xu Z, Teng J. Crustal structure and variability of the Himalayan border of Tibet. Nature, 1984, 307(5946): 23-25
25 Him A, Sapin M, Lepine J C, et al. Increase in melt traction along south-north traverse below the Tibetan Plateau: Evidence from seismology. Tectonophysics, 1997, 273: 17 - 30
26 Makovsky Y, Klemperer S L, Ratschbacher L, et al. INDEPTH wide-angle reflection observation of P-wave to S-wave conversion from crustal bright spots in Tibet. Science, 1996, 274(5293): 1690 - 1691
27 Makovsky Y, Klemperer S L. Measuring the seismic properties of Tibetan bright spots: Evidence for free aqueous fluids in the Tibetan middle crust. Journal of Geophysical Research, 1999, 104(135): 10795 - 10825
28 Kind R, Ni J, Zhao W, et al. Evidence from earthquake data for a partially molten crustal layer in southern Tibet. Science, 1996, 274(5293): 1692- 1694
29 Stern T A, McBride J H. Seismic exploration of continental strike-slip zones. Tectonophysics, 1998, 286: 63 - 78
30 Teng J, Xiong S. Explosion seismological study for velocity distribution and structure of the crust and upper mantle from Damxung to Yadong of the Xizang Plateau. In: Proceedings of Symposium on Qinghai-Xizang(Tibet) Plateau (Beijing, China) Geological and Ecological Studies of Qinghai-Xizang Plateau. Beijing: Science Press, 1981. 691 - 710
31 Zeng R, Ding Z, Wu Q. A review of lithospheric structures in the Tibetan Plateau and constraints for dynamics. Pure App Geoph, 1995, 145(3-4): 425-443
32 Zhao W, Nelson K D, Project INDEPTH Team. Deep seismic reflection evidence for continental underthrusting beneath southern Tibet. Nature, 1993, 366: 557 - 559
33 Zhao W, Mechie J, Guo J, et al. Seismic mapping of crustal structures beneath the Indus-Yarlung suture, Tibet. Terra Nova, 1997,9:42-46
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