下扬子区同生断裂的形成和演化模拟

SIMULATIONS ON THE FORMATION AND EVOLUTION OF CONTEMPORANEOUS FAULTS IN THE LOWER YANGTZE AREA

笔者将非线性理论和塑性流动理论应用于同生断裂研究,并利用FORTRAN 77语言编写了二维带夹层单元弹塑性非线性等参八结点分析程序,应用于同生断裂的形成和演化模拟,结果表明,同生断裂的生长源于上盘的应力作用。结合地质和地球物理资料分析还说明,太湖穹窿是由于水平应力作用导致盖层底部软弱层塑性流动加厚而产生的向上力源作用的结果。同时还可看到,地堑、地垒的形成与早期的断裂和边界条件有关,是它们组合作用的结果。

In this paper,nonlinear theory and plastic flowing theory are applied to the study of contemporaneous faults, and the analysis program for the simulation of the formation and evolution of the contemporaneous faults have been written by using FORTRAN 77 Language with two-dimention elastic-plastic nonlinear ( equal-parameter, eight-node elements). The study suggests that the growth of contemporaneous faults originated from the stress of the hanging walls. Combining with the geological and geophysical data of the study area, it is also proposed that the formation of the Tai Lake Dome Structure was brought about by the upward-stress due to the soft layers' thickenings resulted from plastic flowing at the bottom of sedimentary cover under the action of horizontal stress-field. In addition, it is suggested that the formation of grabens and horsts would be related to the faults developed in early stage and their boundary conditions, and is the result of their assembled efffects.