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Fourier amplitude spectra of strong motion acceleration: Extension to high and low frequencies
Author(s) -
Trifunac M. D.
Publication year - 1994
Publication title -
earthquake engineering and structural dynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.218
H-Index - 127
eISSN - 1096-9845
pISSN - 0098-8847
DOI - 10.1002/eqe.4290230404
Subject(s) - amplitude , physics , acceleration , fourier transform , spectral line , strong ground motion , seismic moment , displacement (psychology) , field (mathematics) , range (aeronautics) , moment (physics) , scaling , computational physics , geodesy , geology , seismology , ground motion , mathematics , optics , geometry , classical mechanics , materials science , quantum mechanics , psychology , fault (geology) , pure mathematics , composite material , psychotherapist
It is shown how the empirical equations for scaling the Fourier amplitude spectra in the frequency band from ∼0.1 to 25 Hz can be extended to describe the strong motion amplitudes in a much broader frequency range. At long periods, the proposed equations are in excellent agreement with (1) the seismological and field estimates of permanent ground displacement (near field) and (2) the independent estimates of seismic moment (far field). At high frequencies, f ≥ 25 Hz, the spectral amplitudes can be described by exp (− π kf ), where k ranges from 0·02 (near source) to about 0·06 at an epicentral distance of about 200 km. It is also shown how amplification by local soil and geological site conditions can be defined to apply in the same broad frequency range.