珠江三角洲地区断块运动与应力场特征的数值模拟研究

Numerical Simulation of Fault Block Movement and Stress Field Characteristics in the Pearl River Delta Region

珠江三角洲属于断块型三角洲,断块差异运动方式及受断块运动影响的应力场特征尚不明确。建立研究区的三维地质模型,采用热-力学耦合的黏弹塑性材料有限单元方法,模拟研究珠江三角洲地区近10 Ma以来的断块运动特征。结果显示:五桂山、番禺台地和伶仃洋三个块体的地表平均垂向位移受控于莫霍面起伏和断层运动,垂向位移差异与目前基底面埋深对应;应力场表现为垂向应力最大,水平应力场方向受远场边界条件控制,两个水平主应力值差异较小;应力场方向在断层附近发生了明显偏移且量值增加,在断层交汇区出现极大值。

The Pearl River Delta is a fault-block delta,and the different motion modes of the fault blocks and the characteristics of the stress field affected by the motion of the fault blocks are still unclear.The paper established a three-dimensional geological model of the study area,and used thermo-mechanical coupled viscoelastic-plastic material finite element method to simulate and study the movement characteristics of fault blocks in the Pearl River Delta region since the past 10 Ma.The results show that the average vertical displacements of the three blocks of Wugui Mountain,Panyu Platform and Lingding Bay is controlled by the Moho undulation and fault movement,and the difference in vertical displacement corresponds to the buried depth of the basement.The stress field of the area presents as the vertical stress being the major principal,the horizontal stress field is controlled by the far field boundary conditions,and the difference between the two horizontal principal stress values is small.The direction of the stress field shifted significantly near the fault with the increased magnitude,and the maximum value appeared in the intersection area of the fault.