Earthquake processes involve complex phenomena and depends on fault dynamics. Different complex phenomena that occur at various scale control the fault dynamics. Using numerical simulation, results of laboratory experiments can be extrapolated to fault behaviour. Conceptual developments in understanding the physics of earthquakes combined with advances in numerical simulation methodology and High Performance Computing, make it possible to develop a new tool for earthquake studies. Observations made during laboratory experiments can be extrapolated using numerical simulations. Hence, numerical simulations provide a clue on the scalability of laboratory results and are a means to improve understanding on how such micro-scale processes in a gouge layer affects the macroscopic behavior of fault zone. The interface being developed between the software system developed at QUAKES (LSMearth) (Mora et al., 1999, Place and Mora, 2000), and a finite-element based software system - GeoFEM (Iizuka, et al.,1999) will enable simulation of processes occurring at the microscopic scale using the particle-based model (LSMearth) and simulation of processes occurring at the macroscopic scale, such as plastic deformation and wave propagation, using the finite-element method (GeoFEM). Using this approach, the effects of microscopic phenomena on the macroscopic behavior of a large-scale fault system can be studied. This hybrid method will also extend the resolution of numerical experiments of fault zone behavior by allowing more efficient simulation of those parts of models well approximated as a continuum such as elastic regions outside the gouge zone. This paper shows the conceptual design for an interface and some computational result between LSMearth and GeoFEM.