Spectral characteristics of strong ground motions from intermediate-depth Vrancea seismic source

This study focuses on the investigation of spectral characteristics of ground motions recorded from intermediate-depth Vrancea earthquakes using Newmark-Hall-type response spectrum. The database consists of more than 700 horizontal components recorded during 10 Vrancea earthquakes. In the first step of the analysis, the component-to-component variability is assessed and the corresponding influence of various parameters (earthquake magnitude, peak ground acceleration, soil class, position of the seismic station, or instrument type) is evaluated. Subsequently, the correlation between the spectral acceleration and the values of the peak ground motion parameters (acceleration, velocity, and displacement) is investigated. The analyses reveal an important influence of the magnitude and a significant influence of the soil class (in the case of large magnitude earthquakes) on the results. These findings are validated through the use of the analysis of variance (ANOVA) method. The computed response amplification factors for the Newmark-Hall type spectrum are similar with those from other studies in the literature. Finally, a check of three control periods such as T (sub B) , T (sub E) , and T (sub F) of the Newmark-Hall-type spectrum yields results somewhat different from the ones given in the Romanian seismic design code P100-1 or in Eurocode 8.