There are good websites like landslides.nz that have commments on what to do immedately after a slip / landslide
https://landslides.nz/response/
ICON can construct a long term solution. There are different methodologies depending on the job, these may include:
Rock anchors / rock bolts
Confined space anchor drilling
Top down excavation
Rock fall mesh
Reinforced sprayed concrete
Timber or steel pole walls
Designing and constructing a solution to a slip / landslide will generally follow the process described here.