D. Hannich

Seismic Site Effect Modelling Based on In Situ Borehole Measurements in Bucharest, Romania

(1) National Institute for Earth Physics, Bucharest-Magurele, Romania, (bala@infp.ro) (2) Universitat Karlsruhe (TH), Germany (joachim.ritter@gpi.uni-karlsruhe.de) (3) University of Erlangen-Nurnberg, Germany Keywords: site effects, seismic measurements, spectral acceleration, microzonation. Introduction Within the NATO Science for Peace Project 981882 “Site-effect analyses for the earthquake-endangered metropolis Bucharest, Romania” we determined a unique, homogeneous dataset of seismic, soil-mechanic and elasto-dynamic parameters. Ten 50 m deep boreholes were drilled in the metropolitan area of Bucharest in order to recover cores for dynamic tests and to measure vertical seismic profiles. These are used for an updated microzonation map related to earthquake wave amplification. The boreholes are placed near former or existing seismic station sites to allow a direct comparison and calibration of the borehole data with actual seismological measurements. A database is assembled which contains P- and S-wave veloc-ity, density, geotechnical parameters measured at rock samples and geological characteris-tics for each sedimentary layer. Using SHAKE2000 we compute spectral acceleration re-sponse and transfer functions obtained from the in situ measurements. The acceleration re-sponse spectra correspond to the shear-wave amplifications excited in the sedimentary layers from 50 m depth (maximum depth) up to the surface. We present the acceleration response results from four sites. Bucharest, the capital of Romania, with more than 2 million inhabitants, is considered, after Istanbul, the second-most earthquake-endangered metropolis in Europe. It is identified as a natural disaster hotspot by a recent global study of the World Bank and the Columbia Univer-sity (Dilley et al., 2005). Four major earthquakes with moment magnitudes between 6.9 and 7.7 hit Bucharest in the last 68 years. The most recent destructive earthquake of 4 March 1977, with a moment magnitude of 7.4, caused about 1.500 casualties in the capital alone. All disastrous earthquakes are generated within a small epicentral area –the Vrancea region- about 150 km northeast of Bucharest (Figure 1). Thick unconsolidated sedimentary layers below Bucharest amplify the arriving seismic waves causing severe destruction. Thus, disas-ter prevention and mitigation of earthquake effects is an issue of highest priority. There are only a few sites which were investigated coincidently with geophysical and geo-technical techniques to relate the local geology with seismic wave propagation properties in Bucharest City (especially amplitude-amplification properties). Therefore, the main purpose of the NATO SfP Project 981882 is to obtain a unique, homogeneous dataset of soil-mechanic and elasto-dynamic parameters of the subsurface of Bucharest from ten new boreholes to model the so-called seismic site responses. Here we present the seismic measurements and modelling results from 4 selected sites. 1. NATO Science for Peace Project 981882 The zoning of the metropolitan area of Bucharest for seismic amplification pattern (microzona-tion) has been pursued with great effort since the 1977 disastrous event. Geophysical groups at the National Institute for Earth Physics (NIEP) and civil engineers at the National Institute

Non-Conventional Field Screening Methods by Application of Geophysical Techniques to Monitor Natural Attenuation Processes at Contaminated Sites

Soil and groundwater contamination can cause serious damage of existing ecosystems or at least restrict the possible use of land or water. Depending on the mobility of contaminants and their toxicity either remediation measures are required in order to avoid further damages for the environment or, if the pollution is not connected with high risk potential, it can be left to natural attenuation. In both cases an intensive control of the contamination and its further behaviour, transport or migration is necessary. These require generally a comprehensive monitoring network with regular sampling and chemical analysis.

Convergent aspects in engineering and environmental geophysics, illustrated by case histories

The goals, possible solutions and characteristic difficulties, that define convergent aspects in engineering and envfronmental geophysics will be discussed. The two independent branches of applied geophysics, i.e., engineering and environmental geophysies, should both be considered as aids of the geosiences, of the structural engineering and of the environmental research. The key for a succesful application of engineering or environmental geophysical measurements is the conversion of the obtained resuits into terms of structural engineering, geotechnical and hydrogeological language.