A morphometric method to determine neotectonic activity of the Weihe basin in northwestern China

Abstract

In order to study the Holocene activity in the down-faulted Weihe Basin, northwest China, the authors conducted a semi-quantitative morphotectonic analysis of the drainage density using topographic maps (1:50,000) and through field investigation. The results obtained have been supported by drill hole data, repeated geodetic surveying and an isopach map of Quaternary strata. They indicate that the Holocene tectonic activity was characterized by block-faulting of the basement on different scales against a background of southward down tilting, with differential movement of small blocks. The mechanism of block movement is shear extension of the NNE-trending Fenwei Graben System under the action of right-lateral shearing. The method, if as valid as it seems in this investigation, is useful in predicting tectonic style and geological hazard where data other than maps are lacking.