The Marmara region of Turkey was shaken by an earthquake with a magnitude of 7.4 and epicentre in Golcuk on August 17, 1999. In this paper the strong motion data acquired from this earthquake at one location is inspected using Fourier transform and a time-frequency technique using harmonic wavelets developed at Cambridge. Wavelet analysis enables us to see energy distribution in time-frequency plane. There is a need to simulate earthquake motions in laboratory conditions to study specific boundary value problems. Dynamic centrifuge modelling enables us to achieve this. The same technique of wavelet analysis can be applied to centrifuge test data. In this paper we show the occurrence of specific frequency shaking at different times both in real earthquake motion and centrifuge data. This could not have been detected using traditional FFT analysis.