Temporal variability earthquakes

The remaining two observations (v) and (vi) relate to the spatial and temporal variability of earthquake evolution within individual clusters. In the following sections, we investigate the hypothesis that this variability is consistent with pressure diffusion within faults that contain a spatially structured heterogeneous transmissivity field. Detailed results from these investigations at A u are presented in Nascimento et al (2003c). 

Seismic ground motions are randomly variable in time and space and are conunonly modeled as random processes. As far as their temporal variability is concerned, the observation of recorded time histories of ground acceleration immediately reveals their nonstationary nature in terms of amplitude. A more careful analysis also reveals a significant variability of their harmonic content with the time. Figure 1 shows, as an example, a ground motion measured in Kobe, Japan, during the 1995 earthquake. The variation in time of the amplitude is... 

---