SHEAR-WAVE VELOCITIES OF THE QUATERNARY LAYERS, DETERMINED BY MULTI-OFFSET VERTICAL SEISMIC PROFILING (MOVSP) IN BUCHAREST, ROMANIA

The Collaborative Research Center 461 (CRC-461):"Strong Earthquakes: a Challenge for Geosciences and Civil Engineering", was initiated by the University of Karlsruhe, Germany in 1995. From the beginning of the research works, the necessity to know the soil parameters of the Quaternary layers in Bucharest was felt. For linear ground response analyses, first of all shear-wave velocities (v(s)) of the geologic layers must be known. Until 2002 shear-wave velocities of the Quaternary layers were known in Bucharest only in a single borehole of 70 m depth at INCERC (Lungu et al., 1999). In May 2002 a measuring campaign of shear-wave velocities by Multi-Offset Vertical Seismic Profiling (MOVSP), in eight boreholes was financed by the CRC-461. The depth of the boreholes ranges from 30 m until 200 m. After a short description of the applied MOVSP measuring technique, averaged v(s)-values for the main Quaternary layers are presented. This method enables v(s)-measurements only from depths of 20 m downward. Using for the upper layers elder v(s)-values deduced from measurements prior to 2002, a complete v(s)-model, is presented. Mean densities for the Quaternary layers, deduced mainly from geophysical borehole logging (ATLAS-G.I.P. S.A.), complete the model of static soil properties.