abstract

A new form of strong-motion accelerogram (“spectrally maximized record” or “SMR”) and its associated generalized spectrum are proposed for earthquake engineering use. Parameters (e.g., spectral, duration, peak amplitude) of strongmotion records at a given site generally depend significantly on the (arbitrary) azimuthal component, sometimes leading to a crucially deficient description of these parameters if only a single component is used. In this paper, combination of horizontal components using spectral maximization is shown to be effective in minimizing the difficulty. The spectra of the two horizontal components at each site are combined to maximize the resultant spectrum, independently of azimuthal orientation. SMR's of 33 important strong-motion accelerograms (including some New Guinea records) are then calculated from their corresponding spectra. In only 60 per cent of cases is the peak acceleration from a maximized spectrum greater than that of the single components. The bracked duration from the maximized spectrum is always greater. After filtering to provide records in ten frequency bands (0-1 Hz, 1-2 Hz, …, 9-10 Hz), correlations for each band are made between acceleration peaks, spectral energy, magnitudes, and source distances. Reasonably stable estimates of strong-motion parameters appear to be given by spectrally maximized seismograms.

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