关于汶川地震发震机制
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摘要
2008年5月12日汶川8级地震的发震断层是四川龙门山逆冲带的前锋灌县—安县断层,或此断层附近新产生相同产状的断层。发震断层走向NE倾向NW,逆冲兼右行平移。汶川地震的发震机制是印藏陆-陆碰撞后,印度次大陆活塞状嵌入欧亚板块造成青藏高原东部向SEE方向近水平挤压,在龙门山冲断带前锋向东南逆冲到四川盆地,构造应力积累和释放的结果。汶川地震演示了一个青藏高原东缘龙门山隆起的构造模型,即其经由龙门山冲断带的地壳冲断作用和缩短作用而隆升。这与Burchfiel的模型不同,该模型认为龙门山上升是由于韧性下地壳流受到四川盆地高强度地壳阻挡而上涌所致。这两种模型可能各有其适用时间阶段,然而本文的模型是不可或缺的,因汶川地震已显示了它的真实性。
The triggering fault of Ms 8.0 Wenchuan earthquake on May 12th, 2008 is the Guanxian-Anxian fault, the frontal thrust of the Longmenshan thrust belt, or a newly created fault near the Guanxian-Anxian fault with the similar attitude. The triggering fault is a NE trending, NW dipping and mainly of thrusting with dextral strike slip fault. The Wenchuan earthquake is resulted form the tectonic stress accumulation and release in the frontal fault of Longmenshan thrust belt caused by the SEE ward horizontal compression from the eastern Tibet plateau including the Longmenshan toward the northwest margin of Sichuan basin, and the SEE ward horizontal compression is led by the indentation collision and subducton of India continent against the Tibet plateau after the continent-continent collision 50 Ma B.P., which resulted to the crust movement from NNE to NE to NEE to SEE gradually from middle Tibet to eastern Tibet. The Wenchuan earthquake leds to a tectonic model of uplifting of the eastern margin of Tibet plateau, the Longmenshan Mountians, through the upper crust thrusting and shortening in the Longmenshan thrust belt. That is basically different from Burchfiel's model about the Longmenshan uplifting resulted from the ductile lower crust flow eastwart barred by strong Sichuan basin crust and become upwelling. Probably both models worked in the different stages of the Longmenshan uplifling respetively, but our model is essential because we have seen it worked in the Wenchuan earthquake.
The triggering fault of Ms 8.0 Wenchuan earthquake on May 12th, 2008 is the Guanxian-Anxian fault, the frontal thrust of the Longmenshan thrust belt, or a newly created fault near the Guanxian-Anxian fault with the similar attitude. The triggering fault is a NE trending, NW dipping and mainly of thrusting with dextral strike slip fault. The Wenchuan earthquake is resulted form the tectonic stress accumulation and release in the frontal fault of Longmenshan thrust belt caused by the SEE ward horizontal compression from the eastern Tibet plateau including the Longmenshan toward the northwest margin of Sichuan basin, and the SEE ward horizontal compression is led by the indentation collision and subducton of India continent against the Tibet plateau after the continent-continent collision 50 Ma B.P., which resulted to the crust movement from NNE to NE to NEE to SEE gradually from middle Tibet to eastern Tibet. The Wenchuan earthquake leds to a tectonic model of uplifting of the eastern margin of Tibet plateau, the Longmenshan Mountians, through the upper crust thrusting and shortening in the Longmenshan thrust belt. That is basically different from Burchfiel's model about the Longmenshan uplifting resulted from the ductile lower crust flow eastwart barred by strong Sichuan basin crust and become upwelling. Probably both models worked in the different stages of the Longmenshan uplifling respetively, but our model is essential because we have seen it worked in the Wenchuan earthquake.
引文
Burch fiel B C.2004.2003presidential address:new technology,new geological challenges[J].Geological Society of American Today,14:4-9.
Balta B, Chen M, KiddeS. r, Daeron M, et al. 2006. Guidebook for field trip in south and north Tianshan foreland basin, Xinjiang Uygur Autonomous Region, China [J]. California Institute of Technologyand Nanjing University.
China Earthquake Administration. 2008a. Distribution and estimateo f Ms 8.0 Wenchuan earthquake and eflerter shock [EB/OL]. http://ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970004/_content/08_05/30/1212117488687.html
China Earthquake Administration. 2008b. Earthquake parameters of Ms8 Wenchuan earthquake [EB/OL]. http://ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970004/_content/08_05/30/1212119019593.html
China Earthquake Administration. 2008c. Focal processes of Ms8 Wenchuan earthquake [EB/OL]. http://ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970004/_content/08_05/30/1212118520734.html
Cowar d M. 1994. Continental collision. // Hamcick P L ed. Continental Deformation. Pergamon Press, Oxford, New York, Seoul, Tokyo. P264-287.
Dewey J F, Shackleton R M, Chang Chengfa, Sun Yunjin. 1988. The tectonics evolution of the Tibetan plateau. Phil Trans R. Soc Lond Ser. A321, 379-413
Jia D, Wei G, Chen Z, et al. 2006. Longmen Shan fold-thrust belt and its relation to the western Sichuan Basin in central China: New insights from hydrocarbon exploration [J]. AAPG Bulletin, 90(9): 1425-1447.
Lin Ai ming, Fu B, Guo J, et al. 2002. Co-seismic strike-slip and rupture length produced by the 2001 Ms 8.1 Central Kunlun earthquake [J]. Science, v.296: 2015-1017.
Niu Z J, Wang M, Sun H R, et al. 2005. Contemporary velocity field of crustal movement of Chinese mainland from Global Posi-tioning System measurements [J]. Chinese Science Bulletin, 50(9):939-941.
Tappon nier P, Xu Q Z, Roger F, et al. 2001. Oblique stepwise rise and growth of the Tibetan Plateau [J]. Science, 294: 1671-1677.
Tappon nier P, Pelzer G, Arimijo R. 1986. On the mechanism of collision between India and Aisa. // Coward M P and Ries A C, eds. Collision Tectonics. Spec. Publsged. Soc. lond. 19, 115-157.
U. S. G eological Survey. 2008a. Magnitude 7.9 - eastern Sichuan, China [EB/OL]. http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2008ryan.php#details
U. S. G eological Survey. 2008b. Centroid moment tensor solution of eastern Sichuan, China Mw 7.9 earthquake [EB/OL]. http://neic.usgs.gov/neis/eq_depot/2008/eq_080512_ryan/neic_ryan_cmt.html
U. S. G eological Survey. 2008c. Shake map of eastern Sichuan, China M 7.9 earthquake [EB/OL]. http://earthquake.usgs.gov/eqcenter/shakemap/global/shake/2008ryan/
中国 地 震局. 2008a. 汶川8.0级地震余震分布与统计.
http: / /ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970 004/_content/08_05/30/1212117488687.html
中国地 震局. 2008b. 汶川8.0级地震参数.
http: / /ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970 004/_content/08_05/30/1212119019593.html
中国地 震局. 2008c. 汶川8.0级地震震源过程. http://ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970004/_content/08_05/30/1212118520734.html
牛之俊 , 王敏, 孙汉荣, 等. 2005. 中国大陆现今地壳运动速度场的最新观测结果[J], 科学通报, 50 (8): 839-840.
Balta B, Chen M, KiddeS. r, Daeron M, et al. 2006. Guidebook for field trip in south and north Tianshan foreland basin, Xinjiang Uygur Autonomous Region, China [J]. California Institute of Technologyand Nanjing University.
China Earthquake Administration. 2008a. Distribution and estimateo f Ms 8.0 Wenchuan earthquake and eflerter shock [EB/OL]. http://ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970004/_content/08_05/30/1212117488687.html
China Earthquake Administration. 2008b. Earthquake parameters of Ms8 Wenchuan earthquake [EB/OL]. http://ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970004/_content/08_05/30/1212119019593.html
China Earthquake Administration. 2008c. Focal processes of Ms8 Wenchuan earthquake [EB/OL]. http://ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970004/_content/08_05/30/1212118520734.html
Cowar d M. 1994. Continental collision. // Hamcick P L ed. Continental Deformation. Pergamon Press, Oxford, New York, Seoul, Tokyo. P264-287.
Dewey J F, Shackleton R M, Chang Chengfa, Sun Yunjin. 1988. The tectonics evolution of the Tibetan plateau. Phil Trans R. Soc Lond Ser. A321, 379-413
Jia D, Wei G, Chen Z, et al. 2006. Longmen Shan fold-thrust belt and its relation to the western Sichuan Basin in central China: New insights from hydrocarbon exploration [J]. AAPG Bulletin, 90(9): 1425-1447.
Lin Ai ming, Fu B, Guo J, et al. 2002. Co-seismic strike-slip and rupture length produced by the 2001 Ms 8.1 Central Kunlun earthquake [J]. Science, v.296: 2015-1017.
Niu Z J, Wang M, Sun H R, et al. 2005. Contemporary velocity field of crustal movement of Chinese mainland from Global Posi-tioning System measurements [J]. Chinese Science Bulletin, 50(9):939-941.
Tappon nier P, Xu Q Z, Roger F, et al. 2001. Oblique stepwise rise and growth of the Tibetan Plateau [J]. Science, 294: 1671-1677.
Tappon nier P, Pelzer G, Arimijo R. 1986. On the mechanism of collision between India and Aisa. // Coward M P and Ries A C, eds. Collision Tectonics. Spec. Publsged. Soc. lond. 19, 115-157.
U. S. G eological Survey. 2008a. Magnitude 7.9 - eastern Sichuan, China [EB/OL]. http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2008ryan.php#details
U. S. G eological Survey. 2008b. Centroid moment tensor solution of eastern Sichuan, China Mw 7.9 earthquake [EB/OL]. http://neic.usgs.gov/neis/eq_depot/2008/eq_080512_ryan/neic_ryan_cmt.html
U. S. G eological Survey. 2008c. Shake map of eastern Sichuan, China M 7.9 earthquake [EB/OL]. http://earthquake.usgs.gov/eqcenter/shakemap/global/shake/2008ryan/
中国 地 震局. 2008a. 汶川8.0级地震余震分布与统计.
http: / /ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970 004/_content/08_05/30/1212117488687.html
中国地 震局. 2008b. 汶川8.0级地震参数.
http: / /ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970 004/_content/08_05/30/1212119019593.html
中国地 震局. 2008c. 汶川8.0级地震震源过程. http://ww.cea.gov.cn:99/manage/html/8a8520ba1a04b8f0011a04cdf6970004/_content/08_05/30/1212118520734.html
牛之俊 , 王敏, 孙汉荣, 等. 2005. 中国大陆现今地壳运动速度场的最新观测结果[J], 科学通报, 50 (8): 839-840.
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