Evidence of tectonic release from underground nuclear explosions in long-period S waves

The SH waves from 21 underground nuclear explosions at Pahute Mesa (NTS) were used to investigate tectonic release. The equivalent double-couple representation of the tectonic release, which was constrained by waveform modeling and the polarity of sP, is very similar for all the explosions. The average orientation is a right-lateral, strike-slip fault trending N15°W. Seismic moments were determined on the basis of comparisons with two western United States strike-slip earthquakes. BENHAM has the largest tectonic release moment (5.6 × 10^(24) dyne-cm) and STILTON (0.1 × 10^(24) dyne-cm) the smallest of the events studied. In general, the seismic moments increase with the size of the explosion, but the location of the explosion relative to previous explosions can strongly affect the tectonic release. The Pahute Mesa events can be separated into two populations: (1) events which are well separated (>4 km) from previous explosions, and (2) those events which are close (