地电台址构造条件的三维有限元数值模拟

NUMERICAL SIMULATION OF 3—D FINITE ELEMENT METHOD OF THE STRUCTURE CONDITION OF GEOELECTRICAL STATION

本文应用粘弹性三维有限元程序,模拟了在定常速率加载边界条件下,断层对于层状介质应力、应变场的影响,并进而通过应力—应变场与地电阻率变化的关系,最终揭示出断层对地电观测的影响。计算结果表明,断裂所处位置、断裂的力学性质及类型对地电台址的选择有重要意义。破碎且较宽的平行断层对地电信息有一定的阻隔作用,而久不活动的被压实的断裂、垂直断层的中段、雁列式断裂端点对地电信息却有增强作用。另外本文还讨论了发震构造的类型对地电观测的影响,结果表明断错型地震的前兆信息强,而走滑型地震的前兆信息弱。

In this paper, the authors apply the 3-D finite element method of visco-elastic medium to simulate the effect of some kinds of fault on the stress-strain field of layered medium under the lateral boundary condition of a constant rate of displacement loading, and then proceed to bring to light the effect of faults on station location of apparent resistivity through the relation between the stress-strain field and the changes of apparent resistivity.The results show that the mutual location between thegeoelectrical station and fault, and the mechanical features and the types of fault have important significance to the selection of the place of geoelectrical station. Parallel fault which is seriously broken and wide has some obstructive effect on apparent resistivity information, and compact dead fault, the medial part of vertical fault and the ends of transcurrent fault have enlarging effect on apparent resistivity information. The authors also discuss the effect of two different types of seismic fault on the observation of apparent resistivity, the conclusion is that the dislocation earthquake has stronger precursory information than the slip earthquake.