Propagating slip pulses in earthquake ruptures (Heaton, 1990) are studied based on a one-dimensional N-degree-of-freedom dynamical spring-slider system with a constant ratio of static to dynamic frictional forces. Results show that for almost all cases in the study, the rise time of ruptures at a particular site is much smaller than the duration of ruptures along the whole fault. A propagating slip pulse is generated along the fault. Hence, simulation results are in agreement with Heaton's propagating slip-pulse model. (C) 2010 Elsevier B.V. All rights reserved.