汶川8.0级大地震震源机制与构造运动特征
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摘要
根据地震震源机制、断层参数结果,结合GPS测定的同震位移场与构造研究的最新结果,综合分析研究了2008年汶川8级大地震汶川地震发生的地震活动背景、震源应力场、断层构造运动特征及其动力学机制。地震活动性分析研究结果表明,2008年汶川8级大地震是在青藏高原与其周边地域构造运动剧烈,2001年起始的地震活动高潮期的背景下发生的。其长达300km的地震震源断层填补了青藏高原东缘1900年以来存在的8级地震活动的空区。震源机制与区域应力场特征及其动力学机制研究表明,汶川8级地震震源处于南北地震带中南段东部,青藏高原东向扩张与四川盆地的抵抗是该区构造运动的主要特征。汶川地震及其强余震是在一个稳定的、主压应力P轴以北西西-东南东方向为主的震源应力场控制下发生的。说明汶川地震震源区域主要受到四川盆地、华南块体区域应力场的控制并发震的。龙门山断裂带西侧的青藏高原相对于四川盆地发生的东向上升;而东侧的四川盆地相对于青藏高原发生的西向下降构造运动是2008年汶川8级地震发生的主要地震成因即地震发生机制。
In this study,seismicity background,stress fields,seismogenic tectonics and dynamics for the 2008 Wenchuan M8 Earthquake were investigated employing earthquake focal mechanisms,source fault parameters and coseismic displacements from GPS.The results suggest that the 2008 Wenchuan M8 event occurred under the tectonical motion in and around the Qinghai-Tibet plateau during a seismically active period since 2001.The Wenchuan M8 event with the 300 km long earthquake fault occurred on the eastern edge of the Qinghai-Tibet plateau,which filled the seismicity gap zone lacking M8 event from 1990.The eastward extensional motions of the Tibetan plateau and the counter action constitute the main tectonic property.The M8 Wenchuan event and its strong aftershocks occurred under a seismogenic stress field where P-axes align stably in NWW-SEE direction.It implies that the seismogenic stress field for the Wenchuan M8 event is mainly attributable to the actions of the stress fields lying on the southern segment of NSSB,the Shichuan basin and the South China block.The results from the source fault parameters and coseismic displacements from GPS suggest that the tectonic movement of the up-eastward slip of the Qinghai-Tibet plateau on the western side of the Longmen Mountain and the relative down-westward slip of the Sichuan basin might have been the causative mechanism of the 2008 Wenchuan M8 event.
In this study,seismicity background,stress fields,seismogenic tectonics and dynamics for the 2008 Wenchuan M8 Earthquake were investigated employing earthquake focal mechanisms,source fault parameters and coseismic displacements from GPS.The results suggest that the 2008 Wenchuan M8 event occurred under the tectonical motion in and around the Qinghai-Tibet plateau during a seismically active period since 2001.The Wenchuan M8 event with the 300 km long earthquake fault occurred on the eastern edge of the Qinghai-Tibet plateau,which filled the seismicity gap zone lacking M8 event from 1990.The eastward extensional motions of the Tibetan plateau and the counter action constitute the main tectonic property.The M8 Wenchuan event and its strong aftershocks occurred under a seismogenic stress field where P-axes align stably in NWW-SEE direction.It implies that the seismogenic stress field for the Wenchuan M8 event is mainly attributable to the actions of the stress fields lying on the southern segment of NSSB,the Shichuan basin and the South China block.The results from the source fault parameters and coseismic displacements from GPS suggest that the tectonic movement of the up-eastward slip of the Qinghai-Tibet plateau on the western side of the Longmen Mountain and the relative down-westward slip of the Sichuan basin might have been the causative mechanism of the 2008 Wenchuan M8 event.
引文
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[4]许忠淮.东亚地区现今构造应力图的编制[J].地震学报,2001,23(5):492-501.Xu Zonghuai.A present-day tectonic stress map for eastern Asia region[J].Acta Seismologica Sinica,2001,23(5):492-501(in Chinese with English abstract).
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[6]王勇,许厚泽.青藏高原印度洋板块向欧大陆俯冲速率的研究—GPS观测资料的反演结果[J].地球物理学报,2003,46(2):185-190.Wang Yong,Xu Houze.A study on convergence rate of the India plate to Eruasia subduction beneath Qinghai-Xizang plateau-Inversion results from GPS observational data[J].Chinese J.Geophys,2003,46(2):185-190(in Chinese with English abstract).
[7]许忠淮,汪素云,黄雨蕊,等.由大量地震的资料推断我国大陆构造应力场[J].地球物理学报,1989,32(6):636-647.Xu Zhonghuai,Wang Suyun,Huang Yurui,et al.The tectonic stress field ofchines continent deduced from a great number of earthquake[J].Chinese J.Geophys.1989,32(6):636-647(in Chinese with English abstract).
[8]Xu Jiren,Zhao Zhixin,Oike Kazuo.Tectonics Characteristics of Seismogenic Stress Field in East Asia[C]//Fujinawa a Y,et al(eds.).Seismotectonics in Convergent Plate Boundary.Tokyo:Terra Scientific Publishing Company,2002:481-497.
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[11]Froidevaux C,Ricard Y.Tectonic evolution of high plateau[J].Tectonophysics,1987,134:227-238.
[12]Zhao Z X,Oike K,Matsumura K.Stress field in the continental part of China derived from temporal variations of Seismic activity[J].Tectonophysics,1990,178:357-372.
[13]曾融生,丁志峰,吴庆举.喜马拉雅及南藏的地壳俯冲带—地震学证据[J].地球物理学报,2000,43(2):590-599.Zeng Rongsheng,Ding Zhifeng,Wu Qingju.Seismological evidence for the mulitiple incomplete crustal subductions in Himalaya and south Tibet[J].Chinese J.Geophys,2000,43(2):590-599(in Chinese with English abstract).
[14]徐纪人,赵志新,石川有三.中国大陆地壳应力场与构造运动区域特征研究[J].地球物理学报,2008,51(3):770-781.Xu Jiren,Zhao Zhixin,Ishikawa Y.Regional characteristics of crustal stress field and tectonic motions in and around Chinese Mainland[J].Chinese J.Geophys.2008,51:861-869(in Chinese with English abstract).
[15]胡幸平,俞春泉,陶开,等.利用P波初动资料求解汶川地震及其强余震震源机制解[J].地球物理学报,2008,51(6):1711-1718.Hu Xingping,Yu Chunquan,Tao Kai,et al.Focal mechanism solutions of Wenchuan earthquake and its strong aftershocks obtained from initial P-wave polarity analysis[J].Chinese J.Geophys,2008,51(6):1711-1718(in Chinese with English abstract).
[16]张勇,冯万鹏,许力生,等.2008年汶川大地震的时空破裂过程[J].中国科学(D辑),2008,38(10):1186-1194.Zhang Yong,Feng Wanpeng,Xu Lisheng,et al.Spatio-temporal rupture process of the2008great Wenchuan earthquake[J].Science in China(Series D),2009,52(2):145-154
[17]陈运泰.汶川特大地震的震级和断层长度[J].科技导报2008,26(10):26-27.Chen Yuntai.On the magnitude and the fault length of the great Wenchuan earthquake[J].Science&Technology Review,2008,26(10):26-27(in Chinese with English abstract).
[18]陈运泰研究小组:第四版玉树地震震源机制和破裂过程快报,2010.http://www.csi.ac.cn/manage/html/28861611c5c2ba0111c5c558b00001/_content/10_04/17/1271488288058.html.
[19]YamanagaY.http://www.seis.nagoya-u.ac.jp/sanchu/Seismo_Note/.
[20]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[J].地球物理学报,2008,51(4):1066-1073.Zhang Peizhen,Xu Xiwei,Wen Xueze.Slip rates and recurrence intervals of the Longmen Shan active fault zone,and tectonic implications for the mechanism of the May12Wenchuan earthquake,2008,Sichuan,China[J].Chinese J.Geophys,2008,51(4):1066-1073(in Chinese with English abstract).
[21]徐纪人,尾池和夫.南北地震带南段应力场特征及其与板块运动的关系[J].地震学报,1995,17(1):31-40.Xu Jiren,Oike K.Earthquake mechanisms and its implication for tectonic stress field in the Southern part of the North-South Seismic Belt in China[J].Acta Seismologica Sinica,1995,17(1):31-40(in Chinese with English abstract).
[22]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Ms8.0级地震的同震位移场[J].中国科学(D辑)2008,38(1):1195-1206.Group of Crustal movement observation.Coseismic displacement field for the2008Wenchuan Ms8.0earthquake determined by GPS[J].Science in China(Series D),2008,38(1):1195-1206(in Chinese).
[23]Xu Jiren,Zhao Zhixin,Kazuo Oike.Spatio-temporal distributions of seismic activity in East Asian and its relation to the regional stress field[J].Acta Seismologica Sinica,1992,5(2):263-269.
[24]趙志新,松村一男,尾池和夫,等.東アジアにおける地震活動変化の地域特徴と関連性について、(3)中国西部と隣接地域[J].地震,1988,第2輯,41:389-400.Zhao Zhixin,Matsumura K,Oike K,et al.Regional characteristics of temporal variations of seismic activity in east Asia and their mutual relations(3)West China and its Neigboring regions[J].Zisin,1987,(40):593-604(in Japanese with English abstract).
[25]Xu J R,Zhao Z X,Ishikawa Y,et al.Properties of the stress field in and around west China derived from earthquake Mechanism solutions[J].Bulletin of the Disaster Prevention Research Institute,Kyoto University,1988,38:49-78.
[2]Molnar P.A review of the seismicity and the rates of active underthrusting and deformation at the Himalaya[J].Journal of Himalayan Geology,1990,1:131-154.
[3]汪一鹏.青藏高原活动构造基本特征[C]//马宗晋,汪一鹏等主编.青藏高原岩石圈现今变动与动力学.北京:地震出版社,2001:251-262.Wang Yipeng.Principal features of the active tectonics in Qinghai-Xizang Plateau[C]//Ma Zongjin,Wang Yipeng,et al(ed.).Study on the recent deformation and dynamics of the lithosphere of Qinghai-Xizang Plateau.Beijing:Seismological Press,2001:251-262(in Chinese with English abstract).
[4]许忠淮.东亚地区现今构造应力图的编制[J].地震学报,2001,23(5):492-501.Xu Zonghuai.A present-day tectonic stress map for eastern Asia region[J].Acta Seismologica Sinica,2001,23(5):492-501(in Chinese with English abstract).
[5]徐纪人,赵志新.青藏高原及其周围地区区域应力场与构造运动特征[J].中国地质,2006,33(2),275-285.Xu Jiren,Zhao Zhixin.Regional characteristics of stress field and tectonic motions in and around the Tibetan Plateau[J].Geology in China,2006.33(2),275-285(in Chinese with English abstract).
[6]王勇,许厚泽.青藏高原印度洋板块向欧大陆俯冲速率的研究—GPS观测资料的反演结果[J].地球物理学报,2003,46(2):185-190.Wang Yong,Xu Houze.A study on convergence rate of the India plate to Eruasia subduction beneath Qinghai-Xizang plateau-Inversion results from GPS observational data[J].Chinese J.Geophys,2003,46(2):185-190(in Chinese with English abstract).
[7]许忠淮,汪素云,黄雨蕊,等.由大量地震的资料推断我国大陆构造应力场[J].地球物理学报,1989,32(6):636-647.Xu Zhonghuai,Wang Suyun,Huang Yurui,et al.The tectonic stress field ofchines continent deduced from a great number of earthquake[J].Chinese J.Geophys.1989,32(6):636-647(in Chinese with English abstract).
[8]Xu Jiren,Zhao Zhixin,Oike Kazuo.Tectonics Characteristics of Seismogenic Stress Field in East Asia[C]//Fujinawa a Y,et al(eds.).Seismotectonics in Convergent Plate Boundary.Tokyo:Terra Scientific Publishing Company,2002:481-497.
[9]Tapponnier P.et al.Propagating extrusion tectonics in Asia:New insights from simple experiments with plasticine[J].Geology,1982,10(2):614-616.
[10]Molnar P,Tapponnier P.A possible dependence of tectonic strength on the age of the crust in Asia[J].Earth and Planetary ScienceLetters,1981:52:107-114.
[11]Froidevaux C,Ricard Y.Tectonic evolution of high plateau[J].Tectonophysics,1987,134:227-238.
[12]Zhao Z X,Oike K,Matsumura K.Stress field in the continental part of China derived from temporal variations of Seismic activity[J].Tectonophysics,1990,178:357-372.
[13]曾融生,丁志峰,吴庆举.喜马拉雅及南藏的地壳俯冲带—地震学证据[J].地球物理学报,2000,43(2):590-599.Zeng Rongsheng,Ding Zhifeng,Wu Qingju.Seismological evidence for the mulitiple incomplete crustal subductions in Himalaya and south Tibet[J].Chinese J.Geophys,2000,43(2):590-599(in Chinese with English abstract).
[14]徐纪人,赵志新,石川有三.中国大陆地壳应力场与构造运动区域特征研究[J].地球物理学报,2008,51(3):770-781.Xu Jiren,Zhao Zhixin,Ishikawa Y.Regional characteristics of crustal stress field and tectonic motions in and around Chinese Mainland[J].Chinese J.Geophys.2008,51:861-869(in Chinese with English abstract).
[15]胡幸平,俞春泉,陶开,等.利用P波初动资料求解汶川地震及其强余震震源机制解[J].地球物理学报,2008,51(6):1711-1718.Hu Xingping,Yu Chunquan,Tao Kai,et al.Focal mechanism solutions of Wenchuan earthquake and its strong aftershocks obtained from initial P-wave polarity analysis[J].Chinese J.Geophys,2008,51(6):1711-1718(in Chinese with English abstract).
[16]张勇,冯万鹏,许力生,等.2008年汶川大地震的时空破裂过程[J].中国科学(D辑),2008,38(10):1186-1194.Zhang Yong,Feng Wanpeng,Xu Lisheng,et al.Spatio-temporal rupture process of the2008great Wenchuan earthquake[J].Science in China(Series D),2009,52(2):145-154
[17]陈运泰.汶川特大地震的震级和断层长度[J].科技导报2008,26(10):26-27.Chen Yuntai.On the magnitude and the fault length of the great Wenchuan earthquake[J].Science&Technology Review,2008,26(10):26-27(in Chinese with English abstract).
[18]陈运泰研究小组:第四版玉树地震震源机制和破裂过程快报,2010.http://www.csi.ac.cn/manage/html/28861611c5c2ba0111c5c558b00001/_content/10_04/17/1271488288058.html.
[19]YamanagaY.http://www.seis.nagoya-u.ac.jp/sanchu/Seismo_Note/.
[20]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[J].地球物理学报,2008,51(4):1066-1073.Zhang Peizhen,Xu Xiwei,Wen Xueze.Slip rates and recurrence intervals of the Longmen Shan active fault zone,and tectonic implications for the mechanism of the May12Wenchuan earthquake,2008,Sichuan,China[J].Chinese J.Geophys,2008,51(4):1066-1073(in Chinese with English abstract).
[21]徐纪人,尾池和夫.南北地震带南段应力场特征及其与板块运动的关系[J].地震学报,1995,17(1):31-40.Xu Jiren,Oike K.Earthquake mechanisms and its implication for tectonic stress field in the Southern part of the North-South Seismic Belt in China[J].Acta Seismologica Sinica,1995,17(1):31-40(in Chinese with English abstract).
[22]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Ms8.0级地震的同震位移场[J].中国科学(D辑)2008,38(1):1195-1206.Group of Crustal movement observation.Coseismic displacement field for the2008Wenchuan Ms8.0earthquake determined by GPS[J].Science in China(Series D),2008,38(1):1195-1206(in Chinese).
[23]Xu Jiren,Zhao Zhixin,Kazuo Oike.Spatio-temporal distributions of seismic activity in East Asian and its relation to the regional stress field[J].Acta Seismologica Sinica,1992,5(2):263-269.
[24]趙志新,松村一男,尾池和夫,等.東アジアにおける地震活動変化の地域特徴と関連性について、(3)中国西部と隣接地域[J].地震,1988,第2輯,41:389-400.Zhao Zhixin,Matsumura K,Oike K,et al.Regional characteristics of temporal variations of seismic activity in east Asia and their mutual relations(3)West China and its Neigboring regions[J].Zisin,1987,(40):593-604(in Japanese with English abstract).
[25]Xu J R,Zhao Z X,Ishikawa Y,et al.Properties of the stress field in and around west China derived from earthquake Mechanism solutions[J].Bulletin of the Disaster Prevention Research Institute,Kyoto University,1988,38:49-78.
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