  The inhomogeneity of the materials with different physical properties in the
Earth is responsible for a wide variety of spatial and temporal behaviors. In
this work, we study an earthquake fault model based on Olami-Feder-Christensen
(OFC) and Rundle-Jackson-Brown (RJB) cellular automata models with particular
aspects of spatial heterogeneities and long-range stress interactions. In our
model some localized stress accumulators are added into the system by
converting a percentage of randomly selected sites into stronger sites which
are called asperity cells. These asperity cells support much higher failure
stresses than the surrounding regular lattice sites but eventually rupture when
the applied stress reaches their threshold stress. We find that changing the
spatial configuration of those stronger sites generally increases capability of
the fault system to generate larger events, but that the total percentage of
asperities is important as well. We also observe an increasing number of larger
events associated with the total number of asperities in the lattice.
