Modeling tremor with cellular automaton by competing time scales of stress accumulation and rupture propagation.

Abstract:

The Olami-Frder-Christensen model(OFC model) is regular earthquakes cell automaton model that exhibits critical properties such as the GR law or the Omori law. In the conventional OFC model, stress doesn't accumulate during rupture propagation because the rupture propagation time scale is much smaller than the loading time scale in the regular earthquakes. But, this assumption may not reasonable in dealing with the tremor because the tremor is more sensitive and longer duration than regular earthquakes. We introduced a new parameter that represents a degree of balance between rupture propagation time scale and loading time scale. And, we estimate this parameter value from the observations. This parameter of tremors may be two to five orders of magnitude higher than that of regular earthquakes. So, we incorporate this new parameter into a conventional OFC model and simulate numerically how the statistics change. The new OFC model explains the several observational properties of the tremor. 1:The tremor has a longer duration than regular earthquakes of similar size. 2:Tremor can be explained as a swarm of low-frequency earthquakes. 3:The tremor's moment rate power spectrum density is the lorentzian spectrum. 4:The tremor's moment is proportional to the duration. These results suggest that the balance between the rupture propagation time scale and loading time scale is important to characterize the tremor.