The Research About Activity Of Kouzhen-Guanshan Fault In The North Of Weihe Basin

The general research in activity of Kouzhen-Guanshan Fault is carried out in accrodence with the project named the Program of Seismic Evaluation of the Center in Shaanxi province. Kouzhen-Guanshan Fault, the boundary of southern Ordos block and northern Weihe basin, is an important fault. The activity of Kouzhen-Guanshan fault controls and affects the evolution and stability of Weihe basin, as well as the structural elements nearby. Meanwhile, it may cause earthquakes and secondary disasters which will threaten the safety and property of civilians. Consequently, the study has scientific and practical importance. This research combines the fruits of previous research and regional geologic background. By means of prospecting the outcrop and topography of the fault, collecting directed samples from fracture surface, and observing thin sections, the tectonic evolution of the fault can be analyzed. In the meanwhile, borehole profile, seismic refraction section, and mobile leveling data of the cross-fault can provide geometry description and process of dynamics of the fault. From the above comprehensive analysis, it infers that Kouzhen - Guanshan fault has experienced at least three tectonic movements (Caledonian period, Yanshanian period, and Himalayan period). However, Caledonian period and Yanshanian period provided tensional tectonic background, while Himalayan period provided stretching background. Nowadays, because of the far field effect caused by the movement of the Indian Ocean plate and Pacific ocean plate, as well as sinistral rotation of Ordos block, Kouzhen-Guanshan fault is under the regional extensional environment. The activity of western fault is more intensely than that in eastern fault which has a tendency to increase, and the fault activities may cause felt earthquake or moderate earthquake in the future.