Study on seismic effect of two-dimensional Lanzhou basin considering the difference of seismic wave input
By using the spectral element method and the numerical simulation method of multiple transmission boundary,the effects of the two-dimensional structure of Lanzhou basin,which has the characteristics of large basin embedded with small basin,on the surface seismic wave propagation,the surface peak acceleration(PGA)and its amplification coefficient,as well as the amplification characteristics in the frequency domain,under different seismic wave input are discussed.The relationship between the amplifying characteristics of ground motion and the lateral uneven structure of the basin is analyzed.The results show that:1)when the dominant frequency of the input wave is close to the first natural frequency in the deepest part of the small basin,the global resonance phenomenon of the small basin will be induced,and then the distribution characteristics of the ground motion or the amplification coefficient will be significantly changed.The secondary surface waves formed at the edge of a large basin transform into two-order surface waves with significant difference in wave velocity when entering a smaller,looser basin,and the intensity of surface waves formed at the edge of the steeper side of the basin is higher.2)No matter where the seismic wave incident occurred,the most intense seismic motion in the basin concentrated on the edge of the small basin,the area above the edge of the steeper side of the large basin was the subintense seismic amplification area,and the edge area of the side with the lower dip Angle of the basin had no edge effect.3)The basement shape of Lanzhou basin has a strong influence on the distribution characteristics of ground motion,and the amplification coefficient of ground motion is obviously affected by the input wave.The distribution characteristics of ground motion and amplification coefficient of horizontal and vertical components are obviously different,on the vertical component,two significant amplification regions are formed on the steeper edge of the large basin and within the small basin,the strongest amplification effect region is located near the center of the small basin,while the strong amplification region on the horizontal component mainly appears in the edge region of the small basin;In addition,the amplification characteristics in frequency domain at different positions of the surface are also obviously different.
spectral element methodtransmission boundaryLanzhou basinplane wave incidenceseismic effect
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