Y.I. Kolesnikov
К.V. Fedin
N. Luckymore

: Soil Dynamics and Earthquake Engineering

This article describes a method of direct determination of the resonant properties of the near-surface sediments using microtremor records and results of testing the method on the test area. It is shown that the averaging amplitude spectra of a large number of microtremor records makes it possible to extract reliably several lowest modes of compressional and shear standing waves in the near-surface layer. Examples of mapping frequencies of these modes (natural frequencies of the layer) for an area of observations are given. For the fundamental mode of horizontal oscillations, a map of the amplification factors relative to the reference point located on the hard rock is also constructed. In addition, we present the maps of calculated from the natural frequencies, the effective (averaged over the near-surface layer thickness) ratios of shear and compressional velocities Vs/Vp and Poisson ratios. The obtained results were compared with the results of processing the same data using the Nakamura's technique