HR: 0800h
AN: S11A-0269    [Abstracts]
TI: Site Response and Liquefaction Risk Analysis for Bucharest, Romania
AU: * Hannich, D
EM: hannich@agk.uka.de
AF: UNIVERSITY OF KARLSRUHE, KAISERSTR: 12, Karlsruhe, D-76128, Germany
AU: Ehret, D
EM: ehret@agk.uka.de
AF: UNIVERSITY OF KARLSRUHE, KAISERSTR: 12, Karlsruhe, D-76128, Germany
AU: Hoetzl, H
EM: heinz.hoetzl@agk.uni-karlsruhe.de
AF: UNIVERSITY OF KARLSRUHE, KAISERSTR: 12, Karlsruhe, D-76128, Germany
AU: Grandas, C
EM: carlos.grandas@ibf.uka.de
AF: UNIVERSITY OF KARLSRUHE, KAISERSTR: 12, Karlsruhe, D-76128, Germany
AU: Huber, G
EM: gerhard.huber@ibf.uni-karlsruhe.de
AF: UNIVERSITY OF KARLSRUHE, KAISERSTR: 12, Karlsruhe, D-76128, Germany
AU: Bala, A
EM: bala@infp.infp.ro
AF: NATIONAL INSTITUTE OF EARTH PHYSICS, POB MG-2, Bucharest-Magurele, RO-76900, Romania
AB: Bucharest, the capital of Romania, with more than 2 million inhabitants, is considered, after Istanbul, the second- most earthquake-endangered metropolis in Europe. Four major earthquakes with moment-magnitudes between 6.9 and 7.7 hit Bucharest in the last 65 years. All disastrous earthquakes are generated within a small epicentral area - the Vrancea region - about 150 km northeast of Bucharest. Thick unconsolidated sedimentary layers in the area of Bucharest amplify the arriving seismic shear waves causing severe destruction. Thus, pertinent site response analysis combined with liquefaction risk analysis for the city area are of highest priority for the disaster prevention and mitigation of earthquake effects. Within the frame of the Collaborative Research Center (CRC) 461: "Strong Earthquakes: A Challenge for Geosciences and Civil Engineering, at the University of Karlsruhe, Germany, recently detailed field investigations for the near-surface soil layers in Bucharest were performed. These include Seismic Cone Penetration Tests (SCPTU) and seismic refraction measurements for shallow depths. SCPTU is used to obtain a detailed distribution of the shear wave velocities and in situ state parameters of soils. The results are used for site response analysis with linear and non-linear wave-propagation models as well as for a liquefaction risk analysis. Commonly linear-equivalent models are used to simulate the response of the soil during earthquakes. Nevertheless, the linear-equivalent model cannot reproduce non-linear effects like liquefaction, layer isolation, and consolidation during shaking. Thus, a 1-D wave propagation model was used to study the influence of non- linear effects in the site response analysis. Cone resistance, sleeve friction and pore water pressure registered continuous by the SCPTU method until depths of 35m permit to determine by simplified empirical methods the factor of safety and the probability of liquefaction for different soil layers at representative sites in Bucharest. To take the depth of the liquefied layers and the thickness of the covering cohesive layer in account, the liquefaction potential index and the liquefaction severity index were computed for different sites. Contour maps for the whole city area were outlined, showing the risk of ground failure at the ground surface during a specific earthquake.
DE: 7212 Earthquake ground motions and engineering seismology
SC: Seismology [S]
MN: 2007 Fall Meeting