Pseudostatic method of analysis provides an index of stability (FoS) but no information on deformations associated with slope failures

Pseudostatic FoS varies throught an earthquake

Newmark considers behavior of slope when Fos is less than 1.0 i.e. the potential failure mass is not in equilibrium

The yield coefficient, ky, is the horizontal pseudostatic coefficient that will produce an FoS of 1.0.

Accuracy of a sliding block analysis depends on the accuracy of the input motion

Since the potential failure mass is assumed to be rigid, the ground motion at the level of the failure surface should be considered

In-phase – for slopes with very stiff soils and/orsubjected to low-frequency motion

Out-of-phase – for slopes with softer slopes and/or slopes subjected to higher frequency motion.