ACTIVE FAULTS AND THEIR FORMATION MECHANISM IN THE EAST SEGMENT OF QIULITAGE ANTICLINE BELT,KUQA DEPRESSION |
| |
| Authors: | LI Sheng-qiang ZHANG Ling YANG Xiao-ping HUANG Wei-liang HUANG Xiong-nan YANG Hai-bo |
| |
| Affiliation: | 1. Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
2. Earthquake Administration of Hebei Province, Shijiazhuang 050021, China;
3. Key Laboratory of Western China Mineral Resources and Geological Engineering, College of Engineering and Surveying of Chang'an University, Xi'an 710064, China |
| |
| Abstract: | Based on geological and geomorphologic characteristics of the surface faults acquired by field investigations and subsurface structure from petroleum seismic profiles, this paper analyzes the distribution, activity and formation mechanism of the surface faults in the east segment of Qiulitage anticline belt which lies east of the Yanshuigou River and consists of two sub-anticlines:Kuchetawu anticline and east Qiulitage anticline. The fault lying in the core of Kuchetawu anticline is an extension branch of the detachment fault developed in Paleogene salt layer, and evidence shows it is a late Pleistocene fault. The faults developed in the fold hinge in front of the Kuchetawu anticline in a parallel group and having a discontinuous distribution are fold-accommodation faults controlled by local compressive stress. However, trenching confirms that these fold-accommodation faults have been active since the late Holocene and have recorded part of paleoearthquakes in the active folding zone. The fault developed in the south limb near the core of eastern Qiulitage anticline is a low-angle thrust fault, likely a branch of the upper ramp which controls the development of the eastern Qiulitage anticline. The faults lying in the south limb of eastern Qiulitage anticline are shear-thrust faults, which are developed in the steeply dipping frontal limb of the fault-propagation folds, and also characterized by group occurrence and discontinuous distribution. Several fault outcrops are discovered near Gekuluke, in which the Holocene diluvial fans are dislocated by these faults, and trench shows they have recorded several paleoearthquakes. The surface anticlines of rapid growth and associated accommodation faults are the manifestations of the deep faults that experienced complex folding deformation and propagated upward to the near surface, serving as an indicator of faulting at depth. The fold-accommodation faults are merely local deformation during the folding process, which are indirectly related with the deep faults that control the growth of folds. The displacement and slip rate of these surface faults cannot match the kinematics parameters of the deeper fault, which controls the development of the active folding. However, these active fold-accommodation faults can partly record paleoearthquakes taking place in the active folding zone. |
| |
| Keywords: | active fault fold-accommodation fault thrust-fold belt eastern Qiulitage anticline Kuqa depression |
|
|
