Cavity Decoupling of Small Explosions in Limestone

A series of small chemical explosions were conducted in May 2012 at Kirtland Air Force Base, New Mexico, as a part of the HUMBLE REDWOOD III experiments. Two charges of 111 kg of ammonium nitrate and fuel oil were detonated at 7 m depth in limestone. The second explosion was detonated in a small asymmetric cavity produced by the first explosion at the same working point as the first explosion. Light Detection and Ranging (LiDAR) was used to image the cavity and to determine an equivalent spherical radius of 0.82 m. The seismic amplitudes for the cavity shot were reduced by a factor of 3-4 compared to the confined shot in limestone. In this article, we quantify the generation of the small cavity and the seismic decoupling it produced.