The key to constructing an earthquake-resistant building is to minimize the forces acting upon it, rather than to maximize the strength of the building itself. Among the methods used to accomplish this are base isolation systems and energy dissipation devices.
Base isolation refers to the way in which buildings are separated from their foundations by bearing pads. Among the various types of bearings, the lead-rubber kind consist of a central solid lead plug surrounded by alternating layers of rubber and steel stiffening plates. Securely attached to the building and foundations, bearings are rigid vertically but flexible horizontally. When an earthquake occurs, these bearings absorb the shock and help to prevent the building from changing shape or 'deforming.'
Energy dissipation devices, or dampers, are intended to aid the natural capacity of buildings to dampen the shock of earthquakes, but without them undergoing deformation. Since earthquake tremors tend to be horizontal in motion, dampers are often installed as part of a brace between columns and ground beams. Unlike base isolation systems, dampers can be retrofitted to an existing building. There are a number of damping device types, including friction, metallic, viscoelastic and fluid viscous. Dampers are also useful for offsetting the weakening impact of strong winds.