The Sterling Experiment: Decoupling of seismic waves by a shot-generated cavity

The Sterling experiment was detonated at 380 tons of nuclear yield in the Salmon shot-generated cavity on December 3, 1966, at 0615 CST. Sterling data from several seismic stations that had previously recorded Salmon signals are interpreted to give values of the decoupling of seismic waves. In particular, the decoupling is deduced as a function of frequency for shot-generated cavities operated at the yield level for Sterling (380 tons) and the yield level for Salmon (5.3 kT). Because it was not possible to deduce decoupling from two shots of the same yield, decoupling ratios were inferred on the basis of a first-power scaling law of amplitude versus yield. A value of 70 ± 20 is seen for the two yield levels at 1 to 2 cps, but this value reduces in different oscillatory ways to 40 or less above 15 cps. A similar function for 5.3 kT in a mined cavity is derived, which shows decoupling values of about 120 at 1 to 3 cps and values less than 10 above 15 cps. The deduced body-wave magnitude (mb) for Sterling is 1.35.