Discrimination of earthquakes and explosions in the eastern United States using regional high‐frequency data

Abstract

High‐frequency regional records from small earthquakes (1.3 < magnitude < 4), and comparable magnitude explosions, are analyzed to find a reliable seismic discriminant in the eastern U. S. Over 500 digital, vertical‐component seismograms recorded by the New York State Seismic Network 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 and explosions, respectively, in the eastern United States. We find that the high‐frequency P/Lg spectral amplitude ratio in the frequency band 5–25 Hz is a reliable and robust discriminant for classifying these 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 instantaneous explosions and ripple‐fired quarry blasts have somewhat different P/Lg spectral ratios, but as a group are distinctly different from earthquakes.