This study is focused on the inertial effect on slip of and interaction between two earthquake faults based on a two-body slider-slider model in the presence of thermal-pressurized slip-weakening friction and viscosity. The ratio m = m 2 / m 1 , where m 2 and m 1 are the masses of sliders 1 and 2, respectively, is the model parameter to represent the inertial effect. Other model parameters are s (the stiffness ratio), f= f o2 /f o1 (where f oi is the normalized static friction force on the i -th slider, i =1, 2), y=U c2 /U c1 (where U ci is the normalized characteristic displacement of friction law on the i -th slider), and g=h 2 /h 1 (where h i is the normalized viscosity coefficient between the i -th slider and the background plate). Simulation results show that m is important on interaction between the two sliders. Foreshocks and aftershocks/afterslip can be generated on slider 1 or slider 2 when m ≠1. Slider 2 behaves like a slow event when m ≥50. The f, y , and g are the major factors and s is minor one in causing time delay between the two sliders. Slider 2 cannot move when f is higher than a critical value which depends on other model parameters. Interaction and the patterns of motions of the two sliders are different between y 1. The presence of viscosity may increase the predominant period of a slider.