Foundation (engineering)
Foundations are designed to have an adequate load capacity depending on the type of subsoil/rock supporting the foundation by a geotechnical engineer, and the footing itself may be designed structurally by a structural engineer. The primary design concerns are settlement and bearing capacity. When considering settlement, total settlement and differential settlement is normally considered. Differential settlement is when one part of a foundation settles more than another part. This can cause problems to the structure which the foundation is supporting. Expansive clay soils can also cause problems.
Unreinforced masonry building
In California, construction of new unreinforced masonry buildings was prohibited in 1933, and state law (enacted in 1986) required seismic retrofitting of existing structures. Retrofits are relatively expensive, and may include the building being tied to its foundation, tying building elements (such as roof and walls) to each other so that the building moves as a single unit rather than creating internal shears during an earthquake, attaching walls more securely to underlying supports so that they do not buckle and collapse, and bracing or removing parapets and other unsecured decorative elements. Retrofits are generally intended to prevent injury and death to people, but not to protect the building itself. According to the 2006-04 California seismic safety commission report, there are still 7800 URM buildings with no retrofitting in the state, including 1100 in the city of Los Angeles.