Seismic surface waves from Amchitka Island test site events and their relation to source mechanism

Relative shear-wave excitation equivalent to large Nevada Test Site underground explosions was detected for the Amchitka Island test Milrow. Use of Milrow Love waves as match filters enabled detection of these waves on Longshot and Milrow collapse recordings as well. Mechanisms other than tectonic strain release must have produced the Love waves. The Rayleigh waves from the collapse were oppositely polarized relative to Milrow and were delayed by a time increment approximately equal to the expected free-fall time through the postexplosion cavity. A small delay (1 to 2 sec) in the initial phase of long-period components of the source function was detected for Milrow relative to Longshot. A Rayleigh-wave amplitude ratio for Milrow and Longshot was precisely determined by match filtering; this ratio agreed almost exactly with amplitude scaling proportional to the cube root of yield.