Site effect classification based on microtremor data analysis using a concentration–area fractal model

Abstract. The aim of this study is to classify the site effect using concentration–area (C–A) fractal model in Meybod city, central Iran, based on microtremor data analysis. Log–log plots of the frequency, amplification and vulnerability index (k−g) indicate a multifractal nature for the parameters in the area. The results obtained from the C–A fractal modelling reveal that proper soil types are located around the central city. The results derived via the fractal modelling were utilized to improve the Nogoshi and Igarashi (1970, 1971) classification results in the Meybod city. The resulting categories are: (1) hard soil and weak rock with frequency of 6.2 to 8 Hz, (2) stiff soil with frequency of about 4.9 to 6.2 Hz, (3) moderately soft soil with the frequency of 2.4 to 4.9 Hz, and (4) soft soil with the frequency lower than 2.4 Hz.