Seismic ground motion variability over the Bucharest city area

Abstract

The purpose of this work is to investigate how the local soil conditions in the Bucharest area control the ground motion characteristics using all the available acceleration data for large and moderate size Vrancea earthquakes. The proposed comparative analysis shows no systematic variations from one site to the other in agreement with the relatively uniform subsurface structure beneath the city. The main conclusion of this study is that for the particular case of Bucharest and Vrancea earthquakes, basically the microzonation is emphasizing no areas with significant variation in the amplification factor. At the same time, the source radiation is clearly controlling the seismic response depending on the magnitude. Thus, for the largest shocks (Mw > 7), the seismic response in the range of 1–2 s period is exceptionally enhanced leading to the disastrous damage noticed for the high-tall buildings in the city.