Numerical study on the influence of near-fault and far-fault earthquakes on a subway station with emphasis to scattering on the wave propagation

To improve the design of surface structures built on underground structures for safety and earthquake resistance, it is necessary to study the effects of the underground structures on wave propagation scattering and surface ground acceleration. To this end, various parameters must be studied, including input motion, structure embedment, and dimensions of different subway stations. The present study focuses on these parameters by employing a nonlinear cyclic model called ARCS soil's shear modulus reduction and damping ratio increase corresponding to those given by the user. The variations in spectral ratio, affected period range, peak ground acceleration, and peak relative lateral displacement versus relative distance under near-fault and far-fault earthquakes are presented. The results indicate that different amplification or de-amplification effects at different surface positions were produced at each frequency by appearing a significant influence on the dynamic behavior of ground surface, soil layers, and the surface structure when a subway station is present. A 1.3 times increase in the surface ground acceleration when subjected to far-fault earthquakes and a 1.6 times increase in the relative displacement indicated that study parameters have significant influence on the amplification ratio and scattering of wave.