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笔者根据地壳表层地质构造和地震地质研究与地震测深和大地电磁测深成果,运用现代构造解析理论与方法,论证了汶川8.0级特大地震的深部构造环境,探讨了汶川8.0级特大地震震源区的地震断裂和震源断裂基本特征与相互关系,及其形成的地球动力学问题。笔者认为龙门山碰撞造山带深处隐伏壳幔韧性剪切带可能是汶川8.0级特大地震主震区的震源断裂,而地壳表层发育的映秀断裂带、北川断裂带和彭县—灌县断裂带等可能是汶川8.0级特大地震主震区的地震断裂,该区震源断裂与地震断裂既有显著区别,又有密切联系。研究表明,在印度板块与太平洋板块和菲律宾海板块对欧亚板块俯冲碰撞的动力学作用下,形成上扬子地块向青藏高原东缘碰撞—楔入以及青藏高原东缘向东仰冲,深部向东俯冲的动力学态势,造成龙门山碰撞造山带切割莫霍界面的壳幔韧性剪切带向中上地壳扩展,应力高度集中与能量快速释放破裂,从而引起汶川8.0级特大地震的发生,以及大型同震地表破裂带的形成。探索震源断裂与地震断裂区别与联系,对进一步研究地震机制与发震动力学以及防震减灾有重要意义。
Based on the study of surface geology and seismic geology of the crust and the results of seismic sounding and electromagnetic measurements, the author demonstrates the deep tectonic environment of the Wenchuan M 8.0 earthquake using modern tectonic analysis theory and methods. The focal area of Wenchuan M 8.0 earthquake is discussed. The basic features and correlations of earthquake and hypocenters, and the geodynamics problems they formed. The author thinks that the ductile crust-mantle ductile shear zone in the depth of the Longmenshan collision orogenic belt may be the focal fault of the MZ 8.0 Wenchuan earthquake, while the Yingxiu fault zone, the Beichuan fault zone and the Pengxian-Guanxian fault zone May be the earthquake rupture in the main earthquake area of Wenchuan Ms 8.0 earthquake. There is notable difference between the focal fault and the earthquake fault in this area, but also closely related. The study shows that under the dynamic action of subduction collision between the Indian plate and the Pacific plate and the Philippine sea plate on the Eurasian plate, the Upper Yangtze block formed a collision-wedge to the eastern edge of the Qinghai-Tibet Plateau and an upward thrust to the east of the Qinghai-Tibet Plateau. Eastward subduction of the dynamic situation, resulting in the Longmenshan collision orogenic Moho cut the mantle ductile shear zone to the upper crustal expansion, stress concentration and rapid energy release rupture, causing Wenchuan 8.0 magnitude earthquake occurred, As well as the formation of large coseismic surface rupture zone. It is of great significance to further explore the mechanism of earthquake, the dynamics of earthquake occurrence and the earthquake disaster prevention and reduction to explore the difference and connection between the source fault and the earthquake fault.