Spatial correlation of peak ground motions and response spectra

The intensities of ground motions and structural responses at two sites are correlated. The magnitude of the correlation depends on the distance between the sites and the natural vibration periods of the structures. This study investigates the spatial correlation of the peak ground motions and the pseudospectral acceleration (PSA) responses using the California records and the Chi-Chi records. Because the correlation arises from interevent and intraevent variability, the correlations for individual variability alone and for the combined variability are assessed. The analysis results indicate that the spatial intraevent correlation decreases as the separation distance increases and that the magnitude of the correlation of the PSA responses depends on the considered natural vibration periods. The results also indicate that the spatial intraevent correlation of the PSA responses for the California records decays more rapidly than that for the Chi-Chi records. Based on the analysis results, a simple empirical equation to predict the spatially varying correlation coefficient of the PSA responses, which can be employed in seismic-hazard and seismic-risk assessments, is proposed.