Surface fault rupture occurs when the movement of earthquake faults propagates to the surface. Surface faulting can be either vertical (normal or thrust), horizontal (strike-slip), or both. Surface faulting can be devastating to both structures and infrastructure (pipelines, utilities and roads) when they are located in the path of faulting.
The Alquist-Priolo Earthquake Fault Zoning Act of 1972 in California was signed into law to reduce the effects of surface faulting on properties. Fault maps were produced which identify the known higher risk faults and (1) requires land owners to disclose if those faults are located on the property if the property is for sale, and (2) prevents construction of buildings within a set distance of the fault unless specific geological studies are performed. However, the risk remains as there are still remain many buildings constructed prior to 1972 which are located along significant faults in California, buildings located outside of California on similar faults, and buildings located on unknown faults
