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.

Figure 1

gather
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.
Figure 2 |

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.

3/8/1999