Slumping and ejecta sliding accompanying some 10‐ton cratering events

Both inward slumping and outward ejecta sliding are inferred to have occurred in four 10‐ton explosive cratering events in Gulf coastal plain sediments. These inferences result from a comparison of displacements obtained by integration of real‐time velocity data from subsurface gauges with displacements based on post‐shot surveys. The slumping did not occur immediately after crater excavation; it was delayed by more than 5 seconds but less than one day. This delay probably resulted from slow recompaction and resaturation of the ejecta and crater walls on a scale of minutes to hours after the excavation and attendant dilation of the media. Ejecta sliding, probably at a few meters per second, apparently moved concrete blocks on the surface up to 2 meters outward relative to gauges buried at the same initial range. The ejecta sliding was not uniform and may occasionally have included portions of the underlying ground.