Preliminary map of soil's predominant periods in Barcelona using microtremors

In order to evaluate soil effects in the urban area of Barcelona, the Nakam ura's technique has been used to estimate the predominant periods of soils. Noise measurements for 195 sites were performed using a strong motion acce lerograph and a velocimeter. In this work, the resulting preliminary map of predominant periods is presented. The obtained predominant periods are coh erent with the geological and geotechnical features of the area. The analys is of the information has allowed the distinctions among several types of s oil and underlying materials. A predominant period of about 0.06 s is evalu ated for sites located over outcrop Paleozoic rock in the Tibidabo-Collsero la Mountains. For sites consisting of material named tricycle, that is the most extensive and also the most heterogeneous zone, predominant period ran ge from 0.10 s up to 2.0 s depending on the thickness of the surface materi als and the kind and thickness of the underlying materials. In the Besos ri ver two zones are observed: the riverside with periods between 0.50 s and 0 .83 s and a second area with periods between 1.0 and 2.1 s. In the Llobrega t river delta the obtained periods are quite homogeneous with values around 0.72 s. Other predominant periods are found in some tertiary rock outcrop.