This paper takes the concentration of stress in a locked fault as the model of earthquake source and deals with the changes in the stress field in a three layered media under the lateral boundary condition of a constant rate of displacement loading. The "precursory" changes in apparent resistvity at the surface of the media associated with the changes in stress-strain field is also discussed in this paper in order to reveal the possibil way of connecting the spatial-temporal changes in apparent, resistivity to the source process.
The results show that, the existance of viscous material in the media would play a very importont role in the preparatory process:besides of the influence of structure of the media the extent of stress concentration is closely relative to the viscous property of the media also, And the spatial-temporal distribution of apparent resistivity precursor is not only concerned with the stress-strain field but also with the mechanical and electrical structure condition of media within the detective scalein observational stations.