Spectral discrimination of NTS explosions and earthquakes in the southwestern United States using high‐frequency regional data

A high‐frequency seismic station has been operating since March, 1987, near Nelson, NV. Records of earthquakes at regional distances from the station show substantially more energy at frequencies above 10 Hz than records of nuclear tests of comparable magnitude on the Nevada Test Site. This contradicts the predictions made by investigators who have advocated high‐frequency monitoring for nuclear test detection and identification. Measuring the slopes of the P g velocity spectra between 4 and 30 Hz successfully discriminates 11 NTS explosions from 36 earthquakes recorded in the first seven months of operation. The spectral differences may result from the respective source depths, with the earthquakes occurring deeper and in faster material than the explosions.