A discussion on the development model of the concealed fault along the Huangshui River in Xining

Abstract：A few facts observed in recent years show that strong earthquakes occur not only in the exposed surface of active faults but also in some concealed structures. The deformation zone is not only an active fault in the mainland block but also a structural deformation zone with great width, as has been confirmed by a lot of seismic activity data. In order to correctly assess the risk of earthquakes, it is necessary to study the deformation of the stratigraphic model of the structure instead of studying only a single fault. The Huangshui River concealed fault is buried under the city of Xining, and the shallow seismic survey results show that the rupture fault is composed of two normal faults, and the area is across Xining City. Based on a study and analysis of the stratigraphic section, the authors hold that the broad anticline and syncline are composed of Neogene red mudstone, which was formed through deformation. The Huangshui River fault was developed in the core of the anticline, as shown by the relationship between the folds and faults. The Huangshui River concealed fault was formed under the main pressure in northeast direction, composed of two normal faults in the core of the anticline. The fault is on the slideway of Xining basin and belongs to a superficial fault, whose activity is not significant.