汶川8．0级地震构造动力成因分析

Analysis on the Geodynamic Cause of the Wenchuan 8.0 Earthquake

汶川8.0级地震发生在青藏活动地块区的东部边界带,是继2001年昆仑山口西大地震之后青藏块区的又一次巨大地震。根据龙门山推覆逆冲断裂带深浅部构造背景和壳幔结构特征,文中构建了汶川地震的震源简化模型。并依据震源模型的力学抽象建立了孕震过程的动力学方程组,且在简化解释下给出了孕震过程中的应力、应变的解析表达式。应用模型的解析解,并参照龙门山构造区的构造形变观测结果,初步讨论了汶川地震的孕震过程,给出了汶川8.0级地震的孕育过程可达3000多年的结果,指出由于龙门山地区构造形变速率很低,因而导致孕震过程缓慢,大震复发期较长的基本结果。

The 2008 Wenchuan 8.0 earthquake occurred on the eastern boundary of the active Tibet block, and is another strong earthquake in the Tibet block after the 2001 Kunlun 8.1 earthquake. Based on the characters of the structure of crust and mantle and the deep or shallow geological background in the Longmenshan dip fault, this paper constructs a simplified source model of the Wenchuan earthquake, from which dynamic equations from this model are constructed and analytic expressions of stress and strain in the progress of seismogeny are derived. Referring to the geological deformation in the Longmenshah region, we further discuss the process of the Wenchuan earthquake by the analytic solution of the model. The result shows that the process of seismogeny may endure about 3200 years and is very slow and longer because of the lower geological deformation in the Longmenshan region.