Is it possible to earthquake-proof furniture when you have plaster walls?
FEMA Earthquake Prep

According to the PDF, page 5-3


  
  
  Figure 2 shows methods to anchor heavy, tall furniture to 
  vertical wall studs, concrete, or  masonry with steel angle 
  brackets.
  Fasten heavy objects to the building structure and not just 
  to a movable wall in your home or office.
  Even large, heavy objects that appear stable should be 
  secured to the wall.  The heavier the furniture, the stronger 
  the restraints need to be.  A heavily loaded file cabinet 
  requires much stronger restraints to keep it from 
  overturning than a light file cabinet with the same 
  dimensions.  


Plaster walls in this case are no different from drywall walls. The strength is in the vertical 2x4 structure, not the materials used to make it pretty.

Secure the furniture to the wall studs and at the floor if you can. Keep tall items away from beds and door and keep a flashlight close by.