A typical seismic trace, as shown in Figure 1, is nonstationary since it includes parts of low and high variance, albeit its mean is approximately zero. A shot gather, as shown in Figure 2, is nonstationary since each individual trace is usually nonstationary. Furthermore, the hyperbolic shape of the reflection events causes spatial spectral variations.
gather
Figure 2 Shot gather. Shot gathers are nonstationary, because they show regions of distinct variance: The early quite zone, the hyperbolic reflections and the noisy coda at the bottom. |
Many synthetic data sets are stationary since they are generated by simple statistical models. In practice, data sets are often nonstationary. However, the decision if a data set is assumed stationary or nonstationary depends on an application's tolerance for deviations from strict stationarity.