In this paper,the mechanism and characteristics of the two models of "the anomalous stress field" and the difference between them are discussed.The first is the model of "concentrated action of the external stress";and the second,of "locked-up segment" Some extension of them are also considered.
The primary distinction between the two models is as follows:In the first model,the anomalous field is caused by the external stress system,which is concentrated over some specific segments of the fault.And the second is caused by the existence of the "locked-up segment" on the fault which is acted upon by a homogeneous fiels of the external stresses.
The mathematical formulae related to the two models are given in dif-ferent cases in this paper.
The analytical results show that due to the difference among the ac-ting modes and the acted sections of the external stresses (in the first model),or to the difference among the orientations of the related faults and the locations of the locked-up segments (in the second model),the characteristics and the distributions of those anomalous fields will also be different to some extent.But in any case,there is no essential distinction between these two models in the most pasts of their anomalous fie-ids with the exception of a few parts,such as those parts which are very near to the acted segment of external stress,the locked-up segment and the end of the faults.