This chapter discusses a basic energy balance involved in earthquake-induced slope failures. It examines shaking table tests to demonstrate the uniqueness of energy in determining the travel distance of failed soil mass. Mechanical impacts of earthquakes on slope failures may be classified into an inertial effect to drive the soil mass, and a cyclic loading effect to weaken the shear resistance of the slope materials by pore-pressure buildup and disturbance of soil structures. In order to evaluate the potential of slope failures, slip-surface analyses are usually carried out in engineering practice taking account of the earthquake effect by the seismic coefficient. For evaluating the post-failure slope displacements, a Newmark-method or its modified version is used assuming a rigid-block slide on a slip plane, though its practical application may be limited within a small displacement of around 1 m. The chapter describes the theoretical backgrounds for calculating the slope displacement using Newmark-method model.