The Newmark's sliding block analysis method is an engineering that calculates permanent displacements of soil slopes (also embankments and dams) during seismic loading.
Newmark analysis does not calculate actual displacement, but rather is an index value that can be used to provide an indication of the structures likelihood of failure during a seismic event.
[1] The extension owes a great deal to Nicholas Ambraseys whose doctoral thesis[2] on the seismic stability of earth dams at Imperial College London in 1958 formed the basis of the method.
In the special case of earth dams, it is used in conjunction with the shear beam method which can provide the acceleration time history at the level of the failure surface.
It also cannot really take account of pore water pressure built-up during cyclic loading which can lead to initiation of liquefaction and different failures than simple distinct slip surfaces.