A multiple-filter F detector method for medium-aperture seismometer arrays

The generalized F method, developed for teleseismic signal detection at small-aperture arrays, is extended to medium-aperture arrays and regional-distance signals using a multiple-filter technique. The technique allows the continuous estimate of the instantaneous amplitude and phase of the array seismograms, while at the same time allowing time-domain beamforming, making the method applicable to situations where the transit time of the signal across an array is much greater than the signal duration. The method is tested by application to waveform data from 22 seismometer arrays of the International Monitoring System, being set up to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty. A comparison with the results of the traditional signal detection method used by the International Data Centre (IDC) shows that the F detector increases candidate first P associations with IDC Reviewed Event Bulletin events, whereas at the same time halving the overall number of detections. The F method increases the number of associations at 21 of the 22 arrays, and for all signal slownesses.