Simulation of effect of fault structure heterogeneity on seismicity using cellular automata model

A 2-D cellular automata fault model with 81×81 cells was constructed to test its seismicity performance. In a series of tests 4 kinds of fault strength heterogeneity and 6 different strength geometrical distributions were taken. With the model simulation we analyzed how the fault structure heterogeneity affects macroscopic fault failure behavior and generated seismic sequence type. The results show that with increasing degree of heterogeneity the macroscopic deformation and fracture process present from brittle to plastic behavior, and produce 3 different types of seismic sequence, i.e., main shock type, foreshock-main shock-aftershock type and swarm type. In the same time, with increasing fault strength heterogeneity the fracture size distribution more regularly follows the G-R relation. Besides, temporarily the events occur in a certain random process, that is, small events appear randomly, medium size events occur in clusters and large ones emerge quasi-periodically. The event clustering and quasi-periodic occurrences become less significant with the fault heterogeneity increasing. It is also found that the randomness of structural geometric variation may affect characteristics of seismic sequences, but the difference in randomness becomes weaker as degree of heterogeneity increases.