The technique was originally proposed by Nogoshi and Igarashi (1971), and wide-spread by Nakamura (1989). It consists in estimating the ratio between the Fourier amplitude spectra of the horizontal (H) to vertical (V) components of the ambient noise vibrations recorded at one single station.This method relies on the Earth’s own seismic noise, rather than an active seismic source. We can measure vibrations from low frequency noise caused by wind, waves, and anthropogenic activities using hand portable seismometers.