东亚大陆形变应力场格局演化的数值模拟

用数值模拟方法研究了印度板块和欧亚板块碰撞后40 Ma以来青藏高原的挤压隆升、东亚大陆形变及应力场的演化过程.模型将东亚大陆限定在一梯形边界框架之中,大陆岩石层被视为由幂指数律控制的薄层,它上伏在粘滞性较低的软流层之上蠕变流动.模型设定印度板块以5 cm/a的恒定速度向北推进,并视其为青藏高原挤压隆升的主要驱动力.除此可活动边界之外,其余均被设为固定边界.数值模拟结果表明,模型预测的现代水平形变速度和GPS观测的格局吻合很好;数值模拟所确定的中国及邻区之区域构造应力场格局与用地震、地质观测所推断的东亚大陆现代构造应力场也能够吻合.这一结果意味着印度板块和欧亚板块的碰撞、挤压是构成现代中国大陆内部岩石层水平形变及应力场格局的主要驱动力.模型计算还表明,大陆水平形变及应力场格局受多种因素如岩石层的力学参数,特别是边界条件的制约.

NUMERICAL SIMULATION OF THE EVOLUTION OF THE DEFORMATION AND STRESS PATTERNS IN THE EAST ASIA CONTINENT

A numerical simulation is employed to study the evolution of the Tibet Plateau's uplift and the deformations and the stress patterns in the region of EastAsia continent after the collision between Indian and Eurasian plates.In this model the EastAsia continent is limited in a trapezoid geological frame and the continental lithosphere is regard as a continuum thin plate with a power law rheology.It overlies on a relative soft uper mantle.The movement of the Indian plate at the rate of 5 cm/a is assumed to be the main driving force driving the Tibet Plateau's uplift and the lithosphere deformation of the EastAsia continent.The numerical simulation shows that the predicted rates of the horizontal deformations of the EastAsia continent can fit to the results of the GPS observation very well.Meantime,the predicted stress patterns can fit the observation data set too.It implicates that the collision and compression between India and Eurasia plates is the main driving force of the horizontal deformations and the stress field of the EastAsia continent.It also shows that the patterns of the continental deformation are controlled by many factors such as the dynamical parameters of the lithosphere and the boundary conditions as well.