The Alquist-Priolo Earthquake Fault Zoning Act was signed into California law on December 22, 1972, to mitigate the hazard of surface faulting to structures for human occupancy. The act in its current form has three main provisions: 1) It directs the state's California Geological Survey agency (then known as the California Division of Mines and Geology) to compile detailed maps of the surface traces of known active faults. These maps include both the best known location where faults cut the surface and a buffer zone around the known trace(s); 2) It requires property owners (or their real estate agents) to formally and legally disclose that their property lies within the zones defined on those maps before selling the property; and 3) It prohibits new construction of houses within these zones unless a comprehensive geologic investigation shows that the fault does not pose a hazard to the proposed structure. The act was one of several that changed building codes and practices to improve earthquake safety. These changes are intended to reduce the damage from future earthquakes. Background This state law was a direct result of the 1971 San Fernando earthquake (also called the 'Sylmar Earthquake'), which was associated with extensive surface fault ruptures that damaged numerous homes, commercial buildings, and other structures. Surface rupture is the most easily avoided seismic hazard. In January 1972, Governor Ronald Reagan established the Governor’s Earthquake Council as a reaction to the Sylmar quake, whose recommendations led to the act. It went into effect on March 7, 1973. The law was amended a few years later to include a disclosure obligation for real estate licensees. The act was called the Alquist-Priolo State Special Studies Zone Act prior to 1994. The act was amended September 26, 1974; May 4, 1975; September 28, 1975; September 22, 1976; September 27, 1979; September 21, 1990; and July 29, 1991. Earthquake hazards Earthquakes happen when two blocks of the Earth's crust move relative to one another. The place where the blocks meet is called a fault, and faults tend to show up as relatively straight lines on maps. Any structure built directly on top of the fault will be torn in two when the blocks move. Constructing a building to withstand this sort of movement (often several feet in a matter of seconds) is not practical, so it is best to avoid building directly on top of an active fault. The