Surface motion from large underground explosions

Abstract

Seismic effects of several underground nuclear explosions were measured in terms of ground surface motion by suitable seismographs from 1200 ft to nearly 10 miles from the source and with teleseismic instruments at great distances. Prior to the Rainier explosion (a 1.7‐kt nuclear shot detonated 900 ft underground) empirical formulas were developed which predicted ground effects from the Rainier shot and several of the larger HARDTACK II shots with fair accuracy but with certain limitations. The limitations were (1) that at distances greater than a few thousand feet, observed displacements were somewhat larger than the formula predicted, necessitating revision of the formula; (2) that frequencies of ground waves did not exceed 20 cps; and (3) that the source conditions and material were in fair duplication. Ground amplitudes on deep alluvium were, as expected, more than twice the amplitudes at nearly the same distance on rock. Velocity response spectrums of one of the shots have been made and reproduced. The magnitude of the Rainier shot was about 4.0, based on the assumption that the source was contained in a volume of rock comparable to that of an earthquake having the same magnitude. Local travel‐time data indicate that the subbasement rock associated with a speed of about 6.2 km/sec is about 3600 ft beneath the shot points area.

Ponded deposits on asteroid 433 Eros

“…Slope failures can be triggered by agitation when seismic accelerations become comparable to the effective acceleration of gravity (Houston et a!., 1973). The accelerations that would result from impacts can be estimated using seismic data from large terrestrial explosions, which can be fitted by the empirical relation (Carder and Cloud, 1959;Adushkin and Nemchinov, 1994):…”

“…This relation applies in the near field where seismic waves propagate spherically and energy absorption can be neglected (typically 200 km on Earth). At large distance D, seismic energy is typically damped (Carder and Cloud, 1959) by a factor exp(-0.002D), but the damping varies greatly with rock and soil type. Eros has a mean diameter of only 17 krn, so seismic energy from an impact causes ringing in the body with an exponential decay time estimated by 160 s for a typical seismic wave speed of 3 km/s.…”

“…(3) with D = 17 km, and the acceleration decays thereafter with a 160 s time constant. For example, an 8.5 m projectile impacting at 8 km s-I will initiate a global average acceleration of 0.4 em s-2 and will mobilize fine particulates for -200 s. For expected seismic frequencies of a few hertz (Carder and Cloud, 1959), the corresponding amplitudes are approximately millimeter.…”

Release of tectonic strain by underground nuclear explosions

“…The seismic energy released by the Rainier explosion was repo.rted as 10 •' to 10 •8 ergs by Carder and Cloud [1959]. Thus only by assuming very liberal values for the effective cavity radius and strain field can we account.…”

Seismic design technology for Breeder Reactor structures. Volume 3: special topics in reactor structures

“…The test was repeated six years later in conjunction with a second blast in which 1,347,000 lb of explosives were detonated with two time delays of 17 msec each. Studies performed by the U.S. Coast and Geodetic Survey (Carder and Cloud, 1959) have estab-Ushed relationships between charge size, distance from point of detonation, and peak ground acceleration.…”