HR: 1340h
AN: S33A-0301    [Abstracts]
TI: Use of the F Detector at Seismometer Arrays in the Presence of Correlated Noise
AU: * Selby, N D
EM: neil@blacknest.gov.uk
AF: AWE Blacknest, Brimpton, Reading, RG7 4RS United Kingdom
AB: The F detector (Blandford, 1974) provides optimal signal detection at seismometer arrays, provided that the seismic noise is white, Gaussian, and uncorrelated between seismometers in the array. Examples from the seismometer array EKA, Eskdalemuir, UK, show the effect of correlated noise on signal detection using F. Setting a signal-to-noise ratio threshold appropriate for high-frequency teleseismic beams increases the number of false detections on regional, low-frequency beams. By treating the array beam-forming process as a weighted least-squares problem in the frequency domain, the concept of the F detector can be extended to include noise with a known covariance matrix. However, in practice the covariance matrix of the noise is not known. Strategies to deal with this include the use of an a priori model covariance matrix or the calculation of long-term beam averages of F. Such approaches should enable the stable use of the F detector in the presence of correlated noise without setting empirical thresholds on each beam. The combination of the F detector with the wavenumber filtering of Douglas (1998) may also lower the detection thresholds at some seismometer arrays. Blandford,R.R., 1974. An automatic event detector at the Tonto Forest seismic observatory, Geophysics, 39, 633-643. Douglas, A., 1988. Making the most of the recordings from Short-Period Seismometer Arrays. BSSA, 115-117.
DE: 0520 Data analysis: algorithms and implementation
DE: 0910 Data processing
DE: 3270 Time series analysis (1872, 4277, 4475)
DE: 7290 Computational seismology
SC: Seismology [S]
MN: Fall Meeting 2005