An error analysis of frequency-time analysis

The temporal resolution and accuracy of frequency-time analysis (FTAN) as applied to surface-wave dispersion analysis are examined for a period range from 10 to 200 sec. The constant relative bandwidth filter (Dziewonski et al., 1969), optimum bandwidth filter (Inston et al., 1971), and display-equalized filter (Nyman and Landisman, 1977) are carefully examined with respect to their adequacy of application over a broad period range. Among these Gaussian filters, the optimum bandwidth filter gives a better performance for relatively short-period (less than 50 sec) dispersion measurement. To measure surface-wave dispersion for a broad period range, a “matched-filter FTAN” technique is introduced by modifying the “residual dispersion measurement” technique (Dziewonski et al., 1972). A detailed numerical analysis is made on this new technique; the result demonstrates a significant improvement on both the resolution and the accuracy of surface-wave dispersion data extraction over a broad period range up to at least 200 sec.