A Review of Available Free-Field Seismic Data from Underground Nuclear Explosions in Salt and Granite

Abstract

Abstract : This report summarizes the progress that has been achieved to date in a continuing effort to compile a complete sample of free-field ground motion data from underground nuclear tests in salt and granite emplacement media. The primary objective of the study has been to collect the available data into a homogeneous data base which will serve as a useful reference for investigators who are attempting to define theoretical seismic source models for contained explosions in these two media. In Chapter 2 the parameters which are typically used in the description of explosive seismic source functions are defined and some of the assumptions underlying the interpretation of measured subsurface ground motion data are critically analyzed. In particular, it is demonstrated that perturbations due to the presence of the free surface can complicate the interpretation of measurements taken above shot depth and lead to significant overestimates of the steady state value of the reduced displacement potential in some cases. The available free-field data from the Gnome and Salmon explosions in salt and the Hard Hat, Shoal and Pile Driver explosions in granite are summarized in Chapter 3 together with he relevant geologic data describing the environment in which the measurements were made.