汶川M_s8.0地震孕育发生的机制与动力学问题
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摘要
2008年5月12日四川省汶川县发生了M_S8.0强烈地震.发震断层是龙门山断裂带的映秀—北川断裂.分析震前的UPS速度场发现,从巴颜喀拉块体西部到龙门山断裂带沿大约N103°E方向的缩短速率为13.0mm/a,龙门山断裂带的右旋走滑速率1.1mm/a,断裂带处于闭锁状态.四川盆地沿大约N103°E方向有少量的压缩变形,而沿SW方向有少量的拉张变形.同震位移场显示,这次地震可能是巴颜喀拉块体SE向逆冲与四川盆地NW向俯冲同时发生的.应变场分析发现,震前震中区的主压与主张应变率分别为—30.840×10~(-9)/a与13.956×10~(-9)/a,主压应变轴N105.4°E与震源机制解得到的主压应力轴的方向N103°E一致.由本文提出的应力-应变机制得到的断层滑动方向和走向与地表破裂调查和震源机制解得到的结果一致.印度、太平洋和菲律宾海板块与欧洲板块的相互作用是龙门山断裂带积累弹性应变能和孕育汶川地震的长期作用力.苏门达腊大地震使青藏高原和华南块体的相互作用加强,促进了汶川地震的发生.
On 12 May 2008, an M_S 8. 0 earthquake occurred in Wenchuan, Sichuan Provin-ce. The seismogenic fault is Yingxiu — Beichuan fault of the Longmenshan fault zone. Analysis of GPS velocity field before the earthquake discovers that the shortening velocity along the direction of about N107. 5°E from west Bayan Har to the Longmenshan faults is 13. 5 mm/a, the clockwise slipping velocity of the Longmenshan faults is 1. 1 mm/a, the faults are locked. Sichuan Basin shows a little compressing deformation along the direction of about N107° E, and a little expanding deformation along the direction of SW. Co-earthquake displacement field shows that the earthquake may be caused by thrust of Bayan Har block along direction of SE and the downthrust of Sichuan Basin along the direction at NW occurred simultaneously. Analysis of the strain field discovers that the principal compressive and the principal tensile strain rates in the epicenter area are-30. 840×10~(-9)/a and 13. 956×10~(-9)/a respectively before earthquake, and the principal compressive strain axis is in a direction of N105. 4°E which is consistent with the average direction at N107. 5°E of the principal compressive stress axis from focal mechanism result. The earthquake fault trend and slipping direction obtained by the mechanism proposed in the paper are also consistent with the results of the focal mechanism. The interactions of the Indian, the Philippine Sea and the Pacific plates with the Eurasian plate are long-term acting force of accumulating elastic strain energy and generating Wenchuan great earthquake. Sumatra-Andaman great earthquake of Dec. 2004 makes the interactions of Tibetan plateau and South China block to strengthen, which promoted occurrence of Wenchuan earthquake.
On 12 May 2008, an M_S 8. 0 earthquake occurred in Wenchuan, Sichuan Provin-ce. The seismogenic fault is Yingxiu — Beichuan fault of the Longmenshan fault zone. Analysis of GPS velocity field before the earthquake discovers that the shortening velocity along the direction of about N107. 5°E from west Bayan Har to the Longmenshan faults is 13. 5 mm/a, the clockwise slipping velocity of the Longmenshan faults is 1. 1 mm/a, the faults are locked. Sichuan Basin shows a little compressing deformation along the direction of about N107° E, and a little expanding deformation along the direction of SW. Co-earthquake displacement field shows that the earthquake may be caused by thrust of Bayan Har block along direction of SE and the downthrust of Sichuan Basin along the direction at NW occurred simultaneously. Analysis of the strain field discovers that the principal compressive and the principal tensile strain rates in the epicenter area are-30. 840×10~(-9)/a and 13. 956×10~(-9)/a respectively before earthquake, and the principal compressive strain axis is in a direction of N105. 4°E which is consistent with the average direction at N107. 5°E of the principal compressive stress axis from focal mechanism result. The earthquake fault trend and slipping direction obtained by the mechanism proposed in the paper are also consistent with the results of the focal mechanism. The interactions of the Indian, the Philippine Sea and the Pacific plates with the Eurasian plate are long-term acting force of accumulating elastic strain energy and generating Wenchuan great earthquake. Sumatra-Andaman great earthquake of Dec. 2004 makes the interactions of Tibetan plateau and South China block to strengthen, which promoted occurrence of Wenchuan earthquake.
引文
[1] 张培震,徐锡伟,闻学泽等.2008年汶川8． 0级地震发震断裂的滑动速率、复发周期和构造成因.地球物理学报,2008,51(4) :1066-1073 Zhang P Z, Xu X W, Wen X Z, et al. Slip rate and recurrence interval of the Longmen Shan active fault zone, and tectonic implications for the May 12, 2008 Wenchuan earthquake, Sichuan, China. Chinese J. Geophys. (in Chinese), 2008, 51(4) :1066-1073
[2] Parsons T, Chen Ji, Kirby E. Stress changes from the 2008 Wenchuan earthquake and increased hazard in the Sichuan basin. Nature, 2008, doi: 10． 1038/nature0717
[3] 滕吉文,白登海,杨辉等.2008年汶川M_s8． 0地震发生的深层过程和动力学响应.地球物理学报,2008,51(5) :1385-1402 Teng J W, Bai D H, Yang Y H, et al. Deep processes and dynamic responses associated with the Wenchuan M_s8． 0 earthquake of 2008． Chinese J. Geophys. (in Chinese), 2008, 51(5) ,1385-1402
[4] 王卫民,赵连锋,李娟,姚振兴.四川汶川8． 0级地震震源过程.地球物理学报,2008,51(5) :1403-1410 Wang W M, Zhao L F, Li J, Yao Z X. Rupture process of the M_s8． 0 Wenchuan earthquake of Sichuan, China. Chinese J. Geophys. (in Chinese), 2008, 51(5) :1403-1410
[5] 张勇,冯万鹏,许力生等.2008年汶川大地震的时空破裂过程.中国科学,2008,38(10) :1186-1194 Zhang Y, Feng W P, Xu L S, et al. The space-time fractural process of the 2008 Wenchuan great earthquake. Science in China (Series D), 2008,38(10) :1186-1194
[6] 刘启元,陈九辉,李顺成等.汶川M_s8． 0地震:川西流动地震台阵观测数据的初步分析.地震地质,2008,30(3) :584-596 Liu Q Y, Chen J H, Li S C, et al. The M_s8． 0 Wenchuan earthquake: Preliminary results from the western Sichuan mobile seismic array observations. Seismology and Geology (in Chinese), 2008, 30(3) :584-596
[7] 徐锡伟,闻学泽,叶建青等.汶川M_s8． 0地震地表破裂带及其发震构造.地震地质,2008,30(3) :597-629 Xu X W, Wen X Z, Ye J Q, et al. The M_s8． 0 Wenchuan earthquake surface ruptures and its seismogenic structure. Seismology and Geology (in Chinese), 2008, 30(3) :597-629
[8] 何宏林,孙昭民,王世元等.汶川M_s8． 0地震地表破裂带.地震地质,2008,30(2) :359-362 He H L, Sun Z M, Wang S Y, et al. Rupture of the M_s8． 0 Wenchuan earthquake. Seismology and Geology (in Chinese), 2008, 30(2) :359-362
[9] 焦青,杨选辉,许丽卿等.汶川8． 0级地震前后龙门山断裂活动场所特征浅析.大地测量与地球动力学,2008,28(4) :7-37 Jiao Q, Yang X H, Xu L Q, et al. Preliminary study on motion characteristics of Longmenshan fault before and after M_s8． 0 Wenchuan earthquake. Journal of Geodesy and Geodynamics (in Chinese), 2008,28(4) :7-37
[10] Burchfiel B C, Chen Z, Liu Y, Royden L H. Tectonics of the Longmenshan and adjacent regions. Central China. Int. Geol. Rev. 1995, 37(8) :661-735
[11] Densemore A L, Ellis M, Li Y, et al. Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau. Tectonics, 2007, 26: TC4005, doi. 10． 1029/2006TC001987
[12] 许志琴,李化启,侯立玮等.青藏高原东缘龙门山-锦屏造山带的崛起--大型拆离断层和挤出机制.地质通报,2007,26(10) :1262-1276 Xu Z Q, Li H Q, Hou L W, et al. Uplifting of Longmen Shan and Jinping Shan, eastern margin of the Tibetan Plateau: large scale detachment faults and their extrusion mechanism. Geol. Bull. China (in Chinese), 2007, 26(10) :1262-1276
[13] 徐锡伟,闻学泽,陈桂华等.巴颜喀拉地块东部龙日坝断裂带的发现及其大地构造意义.中国科学(D辑),2008,38(5) :529-542 Xu X W, Wen X Z, Chen G H, et al. Discovery of the Longriba Fault zone in eastern Bayan Har block, China and its tectonic implication. Science in China (Series D), 2008, 38(5) :529-542
[14] 张培震,邓起东,张国民等.中国大陆的强震活动与活动地块.中国科学(D辑),2003,33(增刊):12-20 Zhang P Z, Deng Q D, Zhang G M. et al. Active tectonic blocks and strong earthquakes in the continent of China. Science in China (Series D), 2003, 33(Suppl):12-20
[15] 牛之俊,王敏,孙汉荣等.中国大陆现今地壳运动速度场的最新观测结果.科学通报,2005,50(8) :839-840 Niu Z J, Wang M, Sun H R, et al. A newest observed result of present-day crustal movement velocity field in China mainland. Chinese Science Bulletin (in Chinese), 2005,50 (8) :839-840
[16] Avouac J P, Tapponnier P. Kinematic model of active deformation in Central Asia. Geophys Res Lett, 1993, 20:895
[17] Meade B J. Present-day kinematics at the India-Asia collision zone. Geology, 2007,35:81
[18] 马保起,苏刚,侯治华等.利用岷江阶地的变形估算龙门山中段晚第四纪滑动速率.地震地质,2005,27(2) :234-242 Ma B Q, Su G, Hou Z H, et al. Late Quaternary slip rate in the central part of the Long menshan Fault zone from terrace deformation along the Minjiang River. Seismology and Geology (in Chinese), 2005, 27(2) :234-242
[19] 刘宝珺.青藏高原东缘地质及大陆动力学研究的新进展.地质通报,2007． 26(8) :1056-1058 Liu B J.New research evolvement of geology and continental dynamics in the eastern margin of Tibetan Plateau. Geological Bulletin of China (in Chinese), 2007,26(8) :1056-1058
[20] 国家重大科学工程“中国地壳运动观测网络”项目组.GPS测定的2008年汶川M_s8． 0级地震的同震位移场.中国科学(D辑),2008,38(10) :1195-1206 State Major Science Project (The crustal motion observation Network of China) Group. Co-earthquake displacement field surrveying by GPS for the 2008 Wenchuan M_s8． 0 earthquake.Science in China (Ser. D) ,2008,38(10) :1195-1206
[21] 周仕勇.川西邻近地区地震活动性模拟和断层间相互作用研究.地球物理学报,2008,51(1) :165-174 Zhou S Y. Seismicity simulation in Western Sichuan of China based on the fault interactions and its implication on the estimation of the regional earthquake risk. Chinese J.Geophys. (in Chinese), 2008, 51(1) :165-174
[22] 李延兴,张静华,何建坤等.由空间大地测量得到的太平洋板块现今构造运动与板内形变应变场.地球物理学报,2007,50(2) :437-447 Li Y X, Zhang J H, He J K, et al. Current-day tectonic movement and intraplate deformation-strain field obtained from space geodesy in the Pacific Plate. Chinese J. Geophys. (in Chinese), 2007,50(2) :437-447
[23] 徐秉业,刘信声.应用弹性力学.北京:清华大学出板社,1995． 83-88 Xu B Y, Liu X S. Application Elastic Mechanics(in Chinese). Beijing:TSinghua University Press, 1995,83-88
[24] Wang Q, Zhang P Z, Freymueller T E, et al. Present-day crustal deformation in China constrained by global positiong system measurements. Science, 2001,294:574-577
[25] 李延兴,张静华,何建坤等.菲律宾海板块的整体旋转线性应变模型与板内形变-应变场.地球物理学报,2006,49(5) :1339-1346 Li Y X, Zhang J H, He J K, et al. Integral-rotation linear strain model and intraplate deformation-strain field of the Philippine Sea Plate. Chinese J. Geophys.(in Chinese), 2006,49(5) :1339-1346
[26] 王敏,张培震,沈正康等.全球定位系统(GPS)测定的印尼苏门达腊巨震的远场同震地表位移.科学通报,2006,51(3) :365-368 Wang M, Zhang P Z, Shen Z K, et al. Far-field coearthquake surface displacement surveying by Global Positioning System C GPS) of Sumatra-Andaman great earthquake in Indonesia. Chinese Science Bulletin (in Chinese), 2006,51(3) :365-368
[27] 马杏垣主编.中国岩石圈动力学图集.北京:中国地图出版社,1989． 2-68 Ma X Y. Lithosphere Dynamics Atlas in China (in Chinese). Beijing:China Cartographic Publishing House, 1989． 2-68
[28] 陈顒,史培军.自然灾害.北京:北京师范大学出版社,2007． 050-093 Chen Y, Shi P J. Natural Calamity (in Chinese). Beijing:Beijing Normal University Press, 2001． 100-104
[29] 陈顒,黄庭芳.岩石物理学.北京:北京大学出版社,2001． 100-104 Chen Y, Huang T F. Rock Physics (in Chinese). Beijing: Peking University Press, 2001． 100-104
[2] Parsons T, Chen Ji, Kirby E. Stress changes from the 2008 Wenchuan earthquake and increased hazard in the Sichuan basin. Nature, 2008, doi: 10． 1038/nature0717
[3] 滕吉文,白登海,杨辉等.2008年汶川M_s8． 0地震发生的深层过程和动力学响应.地球物理学报,2008,51(5) :1385-1402 Teng J W, Bai D H, Yang Y H, et al. Deep processes and dynamic responses associated with the Wenchuan M_s8． 0 earthquake of 2008． Chinese J. Geophys. (in Chinese), 2008, 51(5) ,1385-1402
[4] 王卫民,赵连锋,李娟,姚振兴.四川汶川8． 0级地震震源过程.地球物理学报,2008,51(5) :1403-1410 Wang W M, Zhao L F, Li J, Yao Z X. Rupture process of the M_s8． 0 Wenchuan earthquake of Sichuan, China. Chinese J. Geophys. (in Chinese), 2008, 51(5) :1403-1410
[5] 张勇,冯万鹏,许力生等.2008年汶川大地震的时空破裂过程.中国科学,2008,38(10) :1186-1194 Zhang Y, Feng W P, Xu L S, et al. The space-time fractural process of the 2008 Wenchuan great earthquake. Science in China (Series D), 2008,38(10) :1186-1194
[6] 刘启元,陈九辉,李顺成等.汶川M_s8． 0地震:川西流动地震台阵观测数据的初步分析.地震地质,2008,30(3) :584-596 Liu Q Y, Chen J H, Li S C, et al. The M_s8． 0 Wenchuan earthquake: Preliminary results from the western Sichuan mobile seismic array observations. Seismology and Geology (in Chinese), 2008, 30(3) :584-596
[7] 徐锡伟,闻学泽,叶建青等.汶川M_s8． 0地震地表破裂带及其发震构造.地震地质,2008,30(3) :597-629 Xu X W, Wen X Z, Ye J Q, et al. The M_s8． 0 Wenchuan earthquake surface ruptures and its seismogenic structure. Seismology and Geology (in Chinese), 2008, 30(3) :597-629
[8] 何宏林,孙昭民,王世元等.汶川M_s8． 0地震地表破裂带.地震地质,2008,30(2) :359-362 He H L, Sun Z M, Wang S Y, et al. Rupture of the M_s8． 0 Wenchuan earthquake. Seismology and Geology (in Chinese), 2008, 30(2) :359-362
[9] 焦青,杨选辉,许丽卿等.汶川8． 0级地震前后龙门山断裂活动场所特征浅析.大地测量与地球动力学,2008,28(4) :7-37 Jiao Q, Yang X H, Xu L Q, et al. Preliminary study on motion characteristics of Longmenshan fault before and after M_s8． 0 Wenchuan earthquake. Journal of Geodesy and Geodynamics (in Chinese), 2008,28(4) :7-37
[10] Burchfiel B C, Chen Z, Liu Y, Royden L H. Tectonics of the Longmenshan and adjacent regions. Central China. Int. Geol. Rev. 1995, 37(8) :661-735
[11] Densemore A L, Ellis M, Li Y, et al. Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau. Tectonics, 2007, 26: TC4005, doi. 10． 1029/2006TC001987
[12] 许志琴,李化启,侯立玮等.青藏高原东缘龙门山-锦屏造山带的崛起--大型拆离断层和挤出机制.地质通报,2007,26(10) :1262-1276 Xu Z Q, Li H Q, Hou L W, et al. Uplifting of Longmen Shan and Jinping Shan, eastern margin of the Tibetan Plateau: large scale detachment faults and their extrusion mechanism. Geol. Bull. China (in Chinese), 2007, 26(10) :1262-1276
[13] 徐锡伟,闻学泽,陈桂华等.巴颜喀拉地块东部龙日坝断裂带的发现及其大地构造意义.中国科学(D辑),2008,38(5) :529-542 Xu X W, Wen X Z, Chen G H, et al. Discovery of the Longriba Fault zone in eastern Bayan Har block, China and its tectonic implication. Science in China (Series D), 2008, 38(5) :529-542
[14] 张培震,邓起东,张国民等.中国大陆的强震活动与活动地块.中国科学(D辑),2003,33(增刊):12-20 Zhang P Z, Deng Q D, Zhang G M. et al. Active tectonic blocks and strong earthquakes in the continent of China. Science in China (Series D), 2003, 33(Suppl):12-20
[15] 牛之俊,王敏,孙汉荣等.中国大陆现今地壳运动速度场的最新观测结果.科学通报,2005,50(8) :839-840 Niu Z J, Wang M, Sun H R, et al. A newest observed result of present-day crustal movement velocity field in China mainland. Chinese Science Bulletin (in Chinese), 2005,50 (8) :839-840
[16] Avouac J P, Tapponnier P. Kinematic model of active deformation in Central Asia. Geophys Res Lett, 1993, 20:895
[17] Meade B J. Present-day kinematics at the India-Asia collision zone. Geology, 2007,35:81
[18] 马保起,苏刚,侯治华等.利用岷江阶地的变形估算龙门山中段晚第四纪滑动速率.地震地质,2005,27(2) :234-242 Ma B Q, Su G, Hou Z H, et al. Late Quaternary slip rate in the central part of the Long menshan Fault zone from terrace deformation along the Minjiang River. Seismology and Geology (in Chinese), 2005, 27(2) :234-242
[19] 刘宝珺.青藏高原东缘地质及大陆动力学研究的新进展.地质通报,2007． 26(8) :1056-1058 Liu B J.New research evolvement of geology and continental dynamics in the eastern margin of Tibetan Plateau. Geological Bulletin of China (in Chinese), 2007,26(8) :1056-1058
[20] 国家重大科学工程“中国地壳运动观测网络”项目组.GPS测定的2008年汶川M_s8． 0级地震的同震位移场.中国科学(D辑),2008,38(10) :1195-1206 State Major Science Project (The crustal motion observation Network of China) Group. Co-earthquake displacement field surrveying by GPS for the 2008 Wenchuan M_s8． 0 earthquake.Science in China (Ser. D) ,2008,38(10) :1195-1206
[21] 周仕勇.川西邻近地区地震活动性模拟和断层间相互作用研究.地球物理学报,2008,51(1) :165-174 Zhou S Y. Seismicity simulation in Western Sichuan of China based on the fault interactions and its implication on the estimation of the regional earthquake risk. Chinese J.Geophys. (in Chinese), 2008, 51(1) :165-174
[22] 李延兴,张静华,何建坤等.由空间大地测量得到的太平洋板块现今构造运动与板内形变应变场.地球物理学报,2007,50(2) :437-447 Li Y X, Zhang J H, He J K, et al. Current-day tectonic movement and intraplate deformation-strain field obtained from space geodesy in the Pacific Plate. Chinese J. Geophys. (in Chinese), 2007,50(2) :437-447
[23] 徐秉业,刘信声.应用弹性力学.北京:清华大学出板社,1995． 83-88 Xu B Y, Liu X S. Application Elastic Mechanics(in Chinese). Beijing:TSinghua University Press, 1995,83-88
[24] Wang Q, Zhang P Z, Freymueller T E, et al. Present-day crustal deformation in China constrained by global positiong system measurements. Science, 2001,294:574-577
[25] 李延兴,张静华,何建坤等.菲律宾海板块的整体旋转线性应变模型与板内形变-应变场.地球物理学报,2006,49(5) :1339-1346 Li Y X, Zhang J H, He J K, et al. Integral-rotation linear strain model and intraplate deformation-strain field of the Philippine Sea Plate. Chinese J. Geophys.(in Chinese), 2006,49(5) :1339-1346
[26] 王敏,张培震,沈正康等.全球定位系统(GPS)测定的印尼苏门达腊巨震的远场同震地表位移.科学通报,2006,51(3) :365-368 Wang M, Zhang P Z, Shen Z K, et al. Far-field coearthquake surface displacement surveying by Global Positioning System C GPS) of Sumatra-Andaman great earthquake in Indonesia. Chinese Science Bulletin (in Chinese), 2006,51(3) :365-368
[27] 马杏垣主编.中国岩石圈动力学图集.北京:中国地图出版社,1989． 2-68 Ma X Y. Lithosphere Dynamics Atlas in China (in Chinese). Beijing:China Cartographic Publishing House, 1989． 2-68
[28] 陈顒,史培军.自然灾害.北京:北京师范大学出版社,2007． 050-093 Chen Y, Shi P J. Natural Calamity (in Chinese). Beijing:Beijing Normal University Press, 2001． 100-104
[29] 陈顒,黄庭芳.岩石物理学.北京:北京大学出版社,2001． 100-104 Chen Y, Huang T F. Rock Physics (in Chinese). Beijing: Peking University Press, 2001． 100-104
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