THE USE OF MICROTREMORS FOR THE DEFINITION OF SOILPROPERTIES AND BEDROCK DEPTH IN AN URBAN AREA

摘要

In the present paper we use microtremor array measurements with both Spatial Autocorrelation Method(SPAC) and spectral ratio of the Horizontal to Vertical component of microtremor recordings (H/Vtechnique) in order to define the vertical soil profiles and the construct 2D and 3D soil models down tobedrock, in a densely populated area. The methodology is validated in the experimental site ofEUROSEISTEST where bedrock depth and detailed Vs profiles are very well known. The array measurements were performed at sixteen (16) sites in the city ofThessaloniki. SPAC method was used to determine phase velocity dispersion curves. An inversion schemewas subsequently applied to determine the Vs profiles at all examined sites. The same measurements wereused to determine the fundamental frequency of soil deposits at every site using the H/V spectral ratio(HVSR). Fundamental frequency was used either to validate the rock depth determined by SPAC methodor to estimate this depth at the sites in which bedrock was not explored, using 1D theoretical transferfunction based on inverted Vs profiles.