Release of tectonic strain by underground nuclear explosions

The strong excitation of SH waves and other phenomena associated with underground nuclear explosions suggest the hypothesis that pre-existing tectonic strain was released by the explosion. The pertinent evidence from the Rainier explosion is reviewed. A calculation of tectonic energy release is made for a simple model in which a spherical cavity is inserted in a prestrained medium. It is tentatively concluded that, although tectonic release does occur, its magnitude is probably too small to affect the character of seismograms. Experiments are suggested which could provide the basis for a better evaluation of the hypothesis.