What is Seismic (Earthquake) protection?
Earthquakes can produce vertical and sidewise vibrations up tp perhaps one G or more, though it is usually much less. The immediate concerns can be divided into two categories, “Operating, Basic Earthquake” (OBE) and “Safe Shutdown, Earthquake” (SSE). OBE protection seeks to have equipment operate during and survive an earthquake. SSE protection merely assures that equipment that shuts down during an earthquake will survive to be used another day. Unfortunately, the amount of vibration items experience in a building can be worsened by that building, the higher in the building, the worse the vibration amplitude, since the elasticity of the joists and columns act as springs, only to resonate with the masses supported at anywhere from 5 Hz to 15 Hz. The best place to be is in the basement, on bedrock. Equipment bolted to the floor and walls (“hard mounted”), survive best, provided the bolts, walls or floor do not break. Equipment mounted on isolator springs are particularly vulnerable sin
