DISCRIMINATION OF EARTHQUAKES AND EXPLOSIONS IN THE EASTERN UNITED-STATES USING REGIONAL HIGH-FREQUENCY DATA

High-frequency regional records from small earthquakes (1.3 < magnitud e < 4), and comparable magnitude explosions, are analyzed to find a re liable seismic discriminant in the eastern U. S. Over 500 digital, ver tical-component seismograms recorded by the New York State Seismic Net work in the distance ranges 10 to 610 km are used. Mean P/Lg spectral ratios in the band 1 - 25 Hz are about 0.5 and 1.25 for earthquakes an d explosions, respectively, in the eastern United States. We find that the high-frequency P/Lg spectral amplitude ratio in the frequency ban d 5 - 25 Hz is a reliable and robust discriminant for classifying thes e events. A linear discriminant function analysis indicates that the P /Lg spectral amplitude ratio method provides discrimination power with a total misclassification probability of about 1%. Single-hole instan taneous explosions and ripple-fired quarry blasts have somewhat differ ent P/Lg spectral ratios, but as a group are distinctly different from earthquakes.