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.

Atmospheric dust dispersal analyzed by granulometry of the Misers Gold Event

“…For R -35 m, Lee and Mazzola [1989] found A = 0.0055 for best fits ejecta data from 16 high explosive and nuclear cratering events. For R -35 m, Lee and Mazzola [1989] found A = 0.0055 for best fits ejecta data from 16 high explosive and nuclear cratering events.…”

“…Measurement of the ejecta mass deposited on these pads after the detonation allowed areal densities to be calculated as a function of range ( Figure 2). Scaling of these data follows Lee and Mazzola [1989], who use nondimensional areal density as a function of nondimensional range: t$/pR = A(r/R) -2'6. Figure 3 shows nondimensional areal densities as a function of scaled range.…”

Application of tephra volume models to ejecta volumes from subsurface explosion experiments

“…These experiments were conducted with setups where material type, depth of burial, explosion energy and number of explosions were varied. Military explosion experiments typically scale deposits distribution relative to crater radius (Lee and Mazzola 1989;Gould and Tempo 1981) relating deposits from craters with diameters from meter to kilometers. Explosions used for this study had ejecta distribution of greater than two times the crater radius (typically >5 m) from experiments conducted between May 2013 and June 2014 (Graettinger et al 2014;Valentine et al 2015a;Graettinger et al 2015a).…”

“…An empirical relationship between crater size and ejecta volume was derived from military blast testing of single explosion craters by Lee and Mazzola (1989), such that VtCv = 1.24 · Vc, where Vc is crater volume. This relationship indicates that the volume of ejecta exceeds that of the surface crater for primary blasts.…”

“…Variations on these methods that include a linear regression model dependent on deposit thickness measurements (Burden et al 2013) have been introduced to move away from the interpretation required in the production of isopach maps inherent to the previous methods. Studies focused on crater morphology, such as military blast experiments, have been used to propose empirical relationships between crater size and ejecta volume (Lee and Mazzola 1989). Attempts to correlate crater volume with deposit volume were made by Sato and Taniguchi (1997), who estimated deposit volume using the crystal concentration method, which is based on anticipated crystal abundances relative to a starting magma.…”