This paper presents a detailed analysis on the pattern of drainage systems and the geological structures along the Red Piver Faults and its eastern adjacent area. Together with the results about the earthquake mechanism proposed by precursors, it is pointed out that the stress field in the studied area has been changed since the neotectonic period.
Briefly, before the middle time of the early Pleistocene the compressive stress axis was approximately east-west trending, while in the middle Pleistocene it was northwest-southeast trending. After this, it has turned to northwest north-southeast south trending.
The stress field inferred from the pattern of drainage systems is consistent with the stress field obtained from geological analysis and earthquake mechanism data. This shows that the analysis of drainage systems is a useful approach for this type of research in this particular area.