Method to estimate equivalent natural period with micro-tremor measurements

The object of this paper is to propose a method to estimate the equivalent natural period with micro-tremor measurements on the basis of the correlation between the natural frequency and the yield frequency. A method, combining the Eigensystem Realization Algorithm and some empirical hypotheses of vibration modes, was proposed for identifying the first natural vibration modes of structures. A ratio of the yield frequency to the natural frequency was mostly a certain constant value and the average value of the ratio depends on the type of structures. This paper proposes a simple procedure for estimating the yield frequency with micro-tremor measurements.