HR: 1320h
AN: S43A-0972    [Abstracts]
TI: Seismic Microzonation Based on Geotechnical Parameters - Estimation of Site Effects in Bucharest (Romania)
AU: * Ehret, D
EM: ehret@agk.uka.de
AF: Department of Applied Geology, University of Karlsruhe (TH), Fritz-Haber-Weg 2, Karlsruhe, 76131 Germany
AU: Hannich, D
EM: hannich@agk.uka.de
AF: Department of Applied Geology, University of Karlsruhe (TH), Fritz-Haber-Weg 2, Karlsruhe, 76131 Germany
AB: Romania frequently is hit by strong intermediate depth earthquakes occurring in the Vrancea area in the SE Carpathians. During the 20$^{th}$ century four major earthquakes (moment magnitudes between M$_{W}$ = 6.9 and M$_{W}$ = 7.7) occurred in this region which strongly affected the Romanian capital Bucharest (1.9 mio. inhabitants). Due to the large hypocentral distance between the Vrancea area and Bucharest (approx. 160 km) influences of source directivity and travel path effects are assumed to be constant in the entire city. Therefore significant lateral variations in ground motion must be caused by site effects, related to near-surface geology, mainly dominated by large alluvial and diluvial deposits and anthropogenic backfill. The objective of this study, which is part of the German Collaborative Research Center (CRC) 461 `Strong Earthquakes: A Challenge for Geosciences and Civil Engineering', is to quantify the local influence of site effects on earthquake triggered ground motion and to generate a microzonation map of Bucharest. At first a numerical modelling of ground response was performed by using one-dimensional linear-elastic approaches and geotechnical data, derived from the digital geological subsurface model. The analysis of ground motion was carried out at discrete points. For these raster dots the transfer functions were computed and parameterised by characteristic shake parameters (e. g. dominant frequencies, peak amplifications or spectral amplifications at characteristic frequencies). After spatial interpolation of the computed values these parameters could be presented in continuous microzonation maps. Further the surficial ground motion was computed using a novel (visco-) hypoplastic constitutive law that also takes non-linear soil behaviour into account. The results of both approaches were compared with each other and indicate, that the consideration of non-linear effects is required to get more realistic results for the microzonation.
UR: http://www.agk.uni-karlsruhe.de/projekte/projekte\_ing/mikrozonierung/
DE: 7223 Seismic hazard assessment and prediction
DE: 7205 Continental crust (1242)
DE: 7212 Earthquake ground motions and engineering
SC: Seismology [S]
MN: 2004 AGU Fall Meeting