Study on Modeling Reduction in High-Frequency Component of Input Motion at Heterogeneous Hard-Rock Sites

Abstract

, Spatial incoherence of an earthquake ground motion may result in reduction in high-frequency components of the input motion for a building or a structure. Two-dimensional finite element method is used for heterogeneous soil medium. Through Monte Carlo simulation, the spatially correlated soil model shows more reducing effect in the average input with increasing frequency and with increasing correlation distance. Such effect is caused by the scattering damping and depends on the wavelength, the correlation distance, the traveling distance and the deviation of the soil properties.

Spatial Variation and Its Stochastic Modeling of Seismic Ground Motions in Hard Soil Based on Three-Dimensional-Dense-Array Strong-Motion Observation Records

“…We would like to try to reproduce this in future studies. Previous studies 6), 7) have also failed to reproduce a decrease in coherency at the frequency bands and distance intervals that were the subject of this study simply by introducing velocity and density structure heterogeneity in the site and its vicinity.…”

“…There are two methods of reflecting spatial variation of seismic motion in building design and response evaluation. One method involves replacing all or part of the seismic motion from the hypocenter to the site or to a building on the site (or the building foundation) with a physical model, calculating the seismic motion generating spatial variation by incorporating the abovementioned heterogeneity and irregularity into the model, and determining building response directly 6), 7) . The second method involves finding the building response by simulating wave groups that satisfy the spatial correlation structure of seismic motion obtained statistically from array observation records based on Fourier analysis 8) , and after applying weighting that takes into account the geometric shape of the foundation, synthesizing the waveforms at the contact surface between the building foundation and the ground, which has been discretized into points 4), 9) .…”