Journal of Computational Physics 150, 332–372 (1999) Article ID jcph.1999.6184, available online at http://www.idealibrary.com on The Lattice Solid Model to Simulate the Physics of Rocks and Earthquakes: Incorporation of Friction David Place and Peter Mora 1 QUAKES, The University of Queensland, Brisbane, 4072 Queensland, Australia E-mail: place@earthsciences.uq.edu.au and mora@earthsciences.uq.edu.au Received June 16, 1997; revised November 11, 1998 The particle-based lattice solid model developed to study the physics of rocks and the nonlinear dynamics of earthquakes is refined by incorporating intrinsic friction between particles. The model provides a means for studying the causes of seismic wave attenuation, as well as frictional heat generation, fault zone evolution, and localisation phenomena. A modified velocity–Verlat scheme that allows friction to be precisely modelled is developed. This is a difficult computational problem given that a discontinuity must be accurately simulated by the numerical approach (i.e., the transition from static to dynamical frictional behaviour). This is achieved using a half time step integration scheme. At each half time step, a nonlinear system is solved to compute the static frictional forces and states of touching particle-pairs. Improved efficiency is achieved by adaptively adjusting the time step increment, depending on the particle velocities in the system. The total energy is calculated and verified to remain constant to a high precision during simulations. Numerical experiments show that the model can be applied to the study of earthquake dynamics, the stick–slip instability, heat generation, and fault zone evolution. Such experiments may lead to a conclusive resolution of the heat flow paradox and improved understanding of earthquake precursory phenomena and dynamics. c  1999 Academic Press Key Words: friction; earthquakes; nonlinear dynamics; lattice solid model; particle- based model; heat of earthquakes; fault gouge; numerical simulation; rock physics; heat flow paradox. 1 Affiliations: SSA, AGU, AAAS, SEG. 332 0021-9991/99 $30.00 Copyright c  1999 by Academic Press All rights of reproduction in any form reserved.