  The paper presents results from a recent study in progress, involving an
extensive analysis, based on several deterministic and stochastic indices, of
the frequency content of ground motions recorded during strong Vrancea seismic
events. The study, continuing those initiated by Lungu et al. in the early
nineties, aims to better reveal the characteristics of the analyzed ground
motions. Over 300 accelerograms, recorded during the strong Vrancea seismic
events mentioned above and recently re-digitized, are used in the study.
Various analytical estimators of the frequency content, such as those based on
Fourier spectra, power spectral density, response spectra and peak ground
motion values are evaluated and compared. The results are correlated and
validated by using the information provided by various spectral bandwidth
measures, as the Vanmarcke and the Cartwright and Longuet-Higgins indices. The
capacity of the analyzed estimators to describe the frequency content of the
analyzed ground motions is assessed comparatively and the most relevant
parameters are being identified.
