Geophysics and Geophysical Exploration ISSN:1229-1064(Print) 2384-051X(Online) 지구물리와 물리탐사

This study presents a procedure for discrimination of artificial events from earthquakes occurred in and aroundthe Korean Peninsula using data set in the Wonju KSRS seismograph network, Korea. Two training sets representingnatural and artificial earthquakes were constructed with 150 and 56 events, respectively, with high signal to noise ratio. A frequency band, Pg(4-6 Hz)/Lg(5-7 Hz), which is optimal for the discrimination of seismic sources was derived fromthe two-dimensional grid of Pg/Lg spectral amplitude ratio. The corrections for the effects of earthquake magnitude andhypocentral distance were carried out for improvement of discrimination capability. For correcting the effect of magnitudedependence due to the inverse proportionality of corner frequency to seismic moment, the Brune’s source spectrum wassubtracted from the observation spectrum. The spectrum was corrected using the optimal damping coefficient to removedamping effect with the hypocentral distance. The effect of locally varying spectrum ratio was cancelled correctingvariation of wave propagation along the ray path. The performance in discrimination between training sets of natural andartificial events was compared using the Mahalanobis distance in each step of correction. The procedure of magnitude,distance, and path corrections show clear improvements of the discrimination results with increasing Mahalanobis distance,from 1.98 to 3.01, between two training sets