Nonstationary Signals and Spectral Properties
Yanghua Wang · 2022
When seismic waves propagate through the viscoelastic media in the Earth subsurface, seismic signals have variable properties along with the travel path and travel time. Therefore, seismic signals are nonstationary signals which have time-dependent properties, such as the time period, frequency, and spectral contents. A non-stationary signal cannot be properly represented by the classic Fourier transform, since the amplitude and the frequency of a sinusoid representation may change dynamically with respect to the travel time. For examining local properties of a nonstationary signal, an analytic signal-based analysis method may be employed instead.