The 5.8 magnitude quake that happened in Virginia in 2011 and caused substantial damage to the Washington Monument and National Cathedral also damaged the exterior facade of the 16 story condominium building I live in. Frequently damage was directly related to the height of the structure. My condo unit is on the 12th floor of the building and there was apparently some movement as some books fell off the top shelf of a couple of bookcases.
My 56 inch tall floor-standing loudspeakers did not fall over which was the first audio related thing I thought about when the earthquake happened.
One of the possibly mitigating factors that prevented any damage may have been the design of the footers used under the the speakers. They are a ball and cup design which allows a controlled amount of lateral movement through 360 degrees in the horizontal plane.




Flange-Mount Ball Transfer, Standard, 1" Steel Ball, Steel Housing, 135 lb Capacity
The size of cup shown above will a 1inch diameter ball. picture courtesy of McMaster Carr part No. 5674K61
Obviously if there is too much shaking nothing will help but this is another approach to helping with the problem.
This is similar to the design used under sky-scapers in quake zones to prevent toppling.
The trick is to get a suitable size cup to work with the available Ball Transfer caster sizes. Mine were supplied with my loudspeakers.
Scotty