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On the north side of the Hexi Corridor, two active faults, which belong to two different fault systems, have been discovered on the southern margin of Beishan, namely the Jiujing-Bantan fault and the Ebomiao fault. The NE-trending (40°~50°) Jiujing-Bantan fault with a NW-trending dip angle of 60°~70° is ~28 km long and ~55 km away from Yumen City. It consists of 4 branches and presents a complex Y-shaped distribution, controlling the development of the two late Pleistocene basins on its west side. The nearly EW-trending Ebomiao fault with a NW-trending dip angle of 60°~80° is ~18 km long and ~50 km away from Jinta County. Base on results from the satellite image interpretation, offset geomorphological survey, trench excavation and optical luminescence dating, we discovered a series of ridges, gullies and terraces offset by the Jiujing-Bantan fault which has been active since ~20 ka ago mostly with normal left-lateral strike-slips. The northward thrusting of the Ebomiao fault formed a clear linear scarp and offset the gullies with left-lateral strike-slips. This fault has been active since ~30 ka ago, mainly with reverse left-lateral strike-slips. The neotectonic activities of these two faults evidences that the long-range strain transmission from the northern margin of the Tibetan Plateau has entered into the southern margin of the Beishan orogenic belt since the late Cenozoic.

Three-dimensional numerical simulation for clarifying the seismic response characteristics of an underground structure considering the influences of dynamic interaction with the surrounding liquefied soil is still a huge challenge. Using the proposed generic loosely coupled nonlinear effective stress method for site response of liquefiable soil, the authors developed an effective stress seismic response analysis of the underground subway station structure. Based on the effective stress method, the responses of the model underground subway station with three floors and three spans in model liquefiable foundation in the shaking table test are simulated. The comparison between the measured and simulated results proves that the developed method can effectively capture the response characteristics of the liquefiable foundation，by which the generation of residual excess pore water pressure and the effect of cyclic stiffness softening and degradation can be taken into good consideration, and the measured responses of model underground structure can be well reproduced. The results also demonstrate the availability of the shaking table test simulating the dynamic interaction between the underground structure and the surrounding liquefied soil. [ABSTRACT FROM AUTHOR]