Precise determinations of ionospheric anomaly variations associated with earthquakes require the elimination of other sources of ionospheric variabilities like ionospheric storms, geomagnetic perturbations or geophysical noise. However, revealing the seismo-ionospheric anomalies when the ionosphere is known to be a complex and nonlinear system is of utmost importance. To overcome this constraint, Hilbert-Huang transform (HHT), which is a far better technique for both nonlinear and non-stationary system like ionosphere, was applied together with the cross correlation coefficient method to a 7.0 magnitude earthquake that occurred in Mozambique on 23rd of February, 2006. Three Stations (two within the earthquake preparation zone) with hourly data of f0F2 for one month were used for the study. The results clearly revealed anomalies that are as a result of the earthquake. These were first noticed 10 days and another 3 days before the occurrence of this large earthquake.