This technique is used to obtain information concerning possible dynamic amplification effects of seismic waves in "emersion". It is based on the recording of the background noise in the time domain and following elaboration of the signal’s frequencies in the domain. It is carried out by placing a tridimensional geophone on the ground with low frequency response and by recording the seismic noise in different temporal windows. Later on, the study of the spectrums obtained from the convolution of the frequency of the signal recorded in the domain for the three components of the ground motion and the application of techniques on spectrum analysis, allows to define and measure possible local seismic amplifications and the seismic frequency of the site. The measurements of the microearthquake can also be taken in linear “arrays” for the localization of faults.