Seismic characteristics of underground nuclear detonations

Abstract

An expression is derived for the elastic energy produced by a contained, underground nuclear detonation using an analytic approximation for the pressure profile acting at the elastic radius. The resulting static strain energy and radiated energy equations are evaluated as a function of yield and depth of burial for detonations in tuff and rhyolite. It is shown that, for a given medium, the elastic-energy efficiency depends only on the depth of burial (h) of the device and is proportional to h^0.72. Moreover, for the particular scaling relations used, the strain energy shows the same depth dependence as the radiated energy. Seismic-spectrum scaling theory is applied to an analysis of nuclear seismic-source functions, giving results which are in good agreement with the observed differences in the teleseismic magnitude determinations. A magnitude-energy equation is derived for underground nuclear detonations and is noted to be in poor agreement with the Gutenberg-Richter equation. This discrepancy is interpreted to be an indication that the radiated energy from small earthquakes may typically have been underestimated.