RELIABILITY AND APPLICABILITY OF NAKAMURA'S TECHNIQUE USING MICROTREMORS: AN EXPERIMENTAL APPROACH

Abstract

Nakamura's technique has been widely discussed from the theoretical point of view. Very little information is available as far as the experimental, on-the-field standpoint is concerned. A series of experiments under controlled conditions were set up to assess the reliability and applicability range of this microtremor technique. Since this approach to microzonation is particularly appealing in urban environments, great care was devoted to evaluate the influence of factors such as anthropic noise, concrete or asphalt coverings and soil-structure interaction. Environmental factors (wind) and the influence of sensors were also considered. The results were compared with the seismic response from four earthquakes. The set of experiments shows that under proper measurement conditions Nakamura's technique provides stable and reliable results, but great care has to be devoted to avoid factors that may significantly and adversely affect the results.