摘要
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 surface geological structure of the crust,researches on seismic geology and seismic sounding,and the result of magnetotelluric prospecting,the authors deal with the environment and characteristics of the deep structure and the result of geodynamic analysis of the Great 8.0 Ms Wenchuan earthquake.It is indicated that the concealed crust-mantle ductile shear zone under the Longmen mountain collisional orogenic belts is the focal fault,while Yingxiu fault,Beichuan fault and Pengxian-Guanxian fault formed at surface are earthquake faults in the main focal region of the Great 8.0 Ms Wenchuan Earthquake,which are distinct and connected.Studies show that Great 8.0 Ms Wenchuan Earthquake and surface ruptures might be attributed to the conflict of the Yangtze block with the Qinghai-Tibet plateau and the eastward obduction of the east edge of Qinghai-Tibet plateau and the eastward subduction of its deep part under the dynamic action of India Plate,Pacific Plate and Philippine Plate conflicting with Eurasia plate,which caused Longmen Mountain collisional orogenic belts to cut the Moho-crust-mantle ductile shear zone and expand to the middle-upper crust,thus resulting in high-degree stress concentration and rapid energy release.The study of the relationship between the focal fault and the earthquake fault is of great significance in the investigation of earthquake mechanism,dynamics of earthquake and earthquake disaster prevention and mitigation.
出处
《中国地质》
CAS
CSCD
北大核心
2010年第4期952-966,共15页
Geology in China
基金
国家自然科学基金重点项目(49734150
40234047
40839909)
国土资源部专项计划项目(20001010206)
中石化西南油气分公司项目(GJ-114-0828)
成都市防震减灾局"成都市地震活动断层研究"项目联合资助
