Vertical and horizontal seismic microzonation by microtremor asurement

Abstract

One of the methods by which one can state the dynamic characteristics of the soil of an area, is by the measurement and analysis of microtremors. In this paper microtremors have been measured on 143 sites located in the city of Tabriz, Iran. These sites were chosen on profiles that covered the city in two orthogonal directions. Three components of the microtremors were measured on sediments and associated rock sites. Spectral amplification with respect to rock has been implemented in addition to Nakamura method for HS/VSto interpret the results of measurements for calculation of the natural period of the ground due to horizontal dynamic loadings. Due to the importance of the vertical component of earthquakes, the vertical component of the microtremors has been also studied. On such basis a method was proposed to study the natural period of deposits for vertical ground vibrations.