Empirical decomposition of seismic response for soft soils

In this paper the use of the Hilbert-Huang Transform (HHT), for the decomposition and characterization of seismic ground response, is discussed. The HHT, integrated by the Empirical Mode Decomposition (EMD) and the Hilbert Transformation (HT), enables engineers to analyze non-stationary oscillation systems and to obtain more detailed intensity descriptions on time-varying frequency diagrams. This paper uses the EMD to analyze recordings of accelerations of soft-soil deposits in Mexico City in order to detect and to describe the changes in the ground motion response patterns, as a result of extensive pumping to extract water from subsoil. Conclusions of the analysis of accelerograms indicate that the HHT is able to extract some motion characteristics useful in understanding the evolution of seismic responses of clayey soils, which might not be exposed effectively and efficiently by other conventional data processing techniques.