Consistency of Ground-Motion Estimates Made using System Identification

This article isolates the systematic effects of the soil profile on earthquake ground motions recorded at vertical seismic arrays. An empirical Green’s function is calculated for a soil interval between two sensors in a vertical array. The estimation technique used here falls into the category of site-response estimates but differs from the standard spectral ratio methods in that an extended Weiner filter (ARMA model) becomes the impulse-response function from one point to another in the soil profile. This method allows quantification of the accuracy of predicted ground motions at a given site with normalized mean square prediction errors generally under 10%, indicating effective and consistent estimates. The models are shown to reproduce site ground motions for inputs that differ over a wide range of peak ground acceleration (PGA), hypocentral locations, and over numerous occurrences. We demonstrate consistency of site ground-motion estimates at four sites that have