Problems of Engineering Seismology: article

Аnnotation: The effect on seismic impacts of a thin low-velocity layer overlying a high-velocity rock, which is typical for crystalline shields of ancient platforms, is being studied. The initial data for the analysis are the response spectrum and accelerograms compatible with them on the rock. The peak acceleration value (PGA) is assumed to be 0.11g, which approximately corresponds to an intensity 7 shaking (MSK-64 scale). The site response was calculated using the Monte Carlo approach within the framework of equivalent linear modeling for 4 models differing in the thickness of the upper layer. It has been shown that even a slight increase in the thickness of the low-velocity layer can lead to noticeable increase of the peak acceleration of ground motion and a change in the shape of the response spectrum. The result warns against accepting the seemingly intuitively correct assumption that a slight change in soil thickness (adding 1 m of soil) will have virtually no effect on the parameters of seismic motion on the surface.