The Spatial Coherency of Ground Motions Based on Euroseistest Array

The uniform seismic input for the large-scale or multi-bearing structures, such as bridges cannot reflex the spatial variability of ground motions which could have great effects on the structural dynamic responses. It needs to understand the ground-motion variability within a small area. Based on the ground motions recorded at the dense observation array, EUROSEISTEST located in Greece, the coherences of ground motion at both horizontal and vertical components were investigated under the random vibration theory. The ground-motion coherency for the underground depth was also discussed based on the borehole recordings at varied depths (<; 200 m). The ground-motion coherency at low frequencies in our model showed the approximate consistency with two currently-used models. A remarkable downward tendency of the ground-motion coherency was generally observed with the increase of the frequency or the underground depth. The coherency of ground motions at horizontal components was more significant than that at vertical components.