A three-dimensional analytical study of spatial variability of seismic ground motions

A hybrid deterministic and stochastic method is developed to estimate the spatial variation of seismic ground motions which is necessary for the analysis and design of lifeline systems. An analytical model for wave propagating through a three-dimensional half-space is first proposed to evaluate the ground responses. The incoherent slip over a fault plane is then represented by an autocorrelation function of the dislocation velocity, from which the source motion is modeled as a random process specified by a power spectral density function. To separate the path effect from the source effect, a multi-degree-of-freedom system is chosen as the "substitute system" which is characterized by the equivalent transmission effect to the deterministic wave propagation model. The frequency transfer function of the substitute system is obtained through system identification. With the resulting transfer function of the system and the given power spectral density at the source, the power spectral density of absolute and differential ground motions can be estimated.The results obtained through the model are compared with the field data from an actual earthquake recorded at a dense strong motion array. The analytical results should be applicable for the seismic response analysis and design of pipeline systems.U of I OnlyETDs are only available to UIUC Users without author permissio