Computer processing of Landsat and spot images for the morpho-structural analysis of the Wei He Graben (Shaanxi-China). Preliminary results

Abstract

The Cenozoic Wei He Graben is the most southern of the northern China rift system. It is a half-graben, which southern limit are the ESE-WNW main boundary faults of the Qin Ling Shan Mountains. They correspond to the main eastward-trending faults of the Tibet northern border. A first geological, structural and morphological approach was conducted, based on Landsat multispectral data (MSS, 1:500,000 colour composite images). A geological photo-interpretation and the plotting of important faults (plurikilometric) show the geometry and the general structural pattern of the rift. The morphogical study accounts for vertical movements of large areas but major fault kinematics remains unknown. In order to specify the fault kinematics, a more accurate morpho-structural analysis was conducted, based on spot image processing and interpretation. The preliminary results show that during the Recent Quaternary up to Present, no important strike-slip fault movements (more than 20 m) exist along the Wei He Graben faults as suggested by the pull-apart graben model. In return, the vertical component movements (subsidence) prevail and this agrees with field data.