Outrunning ground shock data from the 100- to 10-psi overpressure decade in six large surface high explosive (HE) tests, three from a rock site and three from a glaciated soil site, were analyzed for the effect of gross changes in constitutive properties. Axisymmetric wave propagation code calculations in layered linear and nonlinear (incrementally elastic-plastic) media were performed to determine the effects of introducing nonlinearity, selected material property variations, and the relative importance of airblast and direct induced effects from surface explosions in the overpressure decade of interest.