Prediction of Vrancea strong motions for design

摘要

The magnitude - recurrence relations for Vrancea earthquakes were established by analysis of the complete seismicity data of this century. For the first time in Romania, mean and mean plus one standard deviation attenuation relations appropriate for the Vrancea intermediate foci (60-160km) were obtained by regression of ground motion parameters (from 4 Vrancea events), as function of magnitude, hypocentral distance and focal depth. The results show the directivity of the attenuation pattern. The diagnosis of the frequency content of the ground acceleration was based on stochastic measures: ε(Cartwright &. Longuet-Higgins) and f_(10), f_(50), f_(90) fractiles of cumulative power of spectral density. The structural response spectra were analysed with emphasis on soft soil condition in Romania, characterised by narrow frequency band motions of 1.5-1.6 s predominant periods.