弹性板块运动模型研究进展

The research progress in elastic plate motion model

传统板块构造理论认为板块是一个刚体,实际上板块是可变形的.板块内部几年到几十年时间尺度的变形主要是弹性变形,因此应当用弹性模型描述板块运动.推导了板块的弹性运动方程,由空间大地测量新的观测成果建立了菲律宾海、太平洋和澳大利亚板块的弹性运动模型.发现三个板块内部都存在明显的水平形变.板内应变场的空间变化有明显的规律:板块边界附近的应变率最大,从边界向内部逐渐减小;在板块扩散边界附近,主张应变率大于主压应变率,主张应变轴基本上与边界的扩张方向一致;在俯冲边界附近,主压应变率大于主张应变率,主压应变轴基本上与板块的俯冲方向一致;在走滑兼有俯冲性质的边界附近,最大剪应变的方向与边界断裂的走向基本一致.由GPS观测得到的主压应变轴与由震源机制解得到的主压应力轴方向具有很好的一致性.板内的应力-应变场基本上遵循广义胡克定律.

The traditional plate tectonic theory considers plate as a rigid body, but really plate is deformable. The plate interior deformations are mainly elastic deformations from years to decades, therefore we shall describe plate motion by elastic model. We derived a plate elastic motion equation, and based on the new space geodetic data, create elastic motion models for Philippine Sea, Pacific and Australian plate. We discover that the horizontal deformation within 3 plates is evident. The spatial variation of strain field within the plates is regular. The strain rate near plate boundary is maximum, and reducing gradually from margin to interior. Near diffuse boundary, the principal tensile strain rate is large than the principal compressive strain rate, and the principal tensile strain axis is basically consistent with the extending direction of the boundary. Near down thrusting boundary, the principal compressive strain rate is Large than principal tensile strain rate, and the principal compressive strain axis is basically consistent with the plate down-thrusting direction. Near striking slip and down-thrusting boundary, the maximum shear strain direction is basically consistent with strike of the margin fault The principal compressive strain axis obtained by GPS observation is well consistent with the principal compressive stress axis obtained by earthquake focal mechanisms. The stress-strain field conformed to generalized Hooke law.