Ejecta scaling laws for craters in dry alluvial sites

Abstract

The existing factor‐of‐20 scatter in the ejecta thickness data, for surface bursts (chemical and nuclear) in dry alluvium, is reduced to a scatter a factor of ∼4 by a simple yield correction. This correction accounts for the mismatch in the scaling laws that govern the formation of the ejecta blanket and of the apparent crater. Craters from surface bursts obey strength scaling, in which linear crater dimensions scale as cube root of the yield. Their ejecta blankets, on the other hand, obey gravity scaling, in which linear ejecta blanket dimensions scale as yield to a power of less than a third. For this reason, geometric scaling (scaling the range and the ejecta thickness by the crater radius) is appropriate for craters in the gravity regime. However, it is not the appropriate scaling rule for ejecta from surface bursts and is the reason for the observed factor‐of‐20 scatter. A simple correlation is proposed that agrees with the data to better than a factor of 2 in the continuous ejecta region, and slightly more than a factor of 2 in the discrete ejecta region. For buried bursts, the craters obey 1/3.4 scaling, a transition between the strength and gravity regimes, while the ejecta blankets scale with gravity. Despite this slight mismatch in the scaling, field data for buried bursts agree with a proposed geometric‐scaled correlation to approximately a factor of 2 in the continuous ejecta region and approximately a factor of 5 in the discrete ejecta region.