Under the seismic microzoning project of Caracas city, has been done since mid 90's several ambient noise measurements in order to determinate fundamentals periods of soil. In this work we showed a new relationship that includes the effect of the surface sediment layers, considering the values of shear-wave velocities for the frst 30 m (Vs30) and the value of Vs to the deepest layer. The results indicate that this relationship generates more accurate estimates of sediment thickness comparing with real values of depth; this relationship was calibrated with information from 4 depth boreholes done in Caracas, obtaining accurate depth values. The main objective for this new relationship is allow for future studies in other cities of country, had a local relationship between period and sediments thickness that considering local information of soils (Vs30 y Vs) to generate accurate sediment thickness maps from environmental noise measurements.