Fault-Rupture Hazards, the Alquist-Priolo Fault Hazard Act, and Siting Decisions in California

Abstract

Most of the earthquake-related studies for urban development in California during the past two decades have been focused on the location of “active faults.” Since 1972 (1 year after the San Fernando earthquake), California law (the Alquist-Priolo Act) has required site-specific studies to locate active faults so that no structure for human occupancy will be built astride a fault which has been active during Holocene time. The political process permitted the original Alquist-Priolo Act to become so limited in scope that to date it has been essentially useless with regard to approximately 99 percent of the earthquake damage losses. The original version of the bill was reasonably good, comprehensive geologic/seismic legislation addressing most of the geologic phenomena which cause damage during earthquakes. Lobbyists representing real estate interests opposed the original bill, but finally agreed to support a bill limited to the fault-rupture hazards only. The studies required by the Alquist-Priolo Act are of questionable economic value inasmuch as the costs may be high while the benefits based on review of historic earthquake damage are very limited. Fault rupture accounts for less than 1 percent of earthquake damage (0 percent of the estimated over $5.9 billion in damages caused by the 1989 Loma Prieta earthquake in California), yet it is the only earthquake hazard specifically addressed by all but one ordinance in California (San Diego has a liquefaction hazard ordinance). The office of the State Geologist is required to put Alquist-Priolo reports on file, but is neither required nor authorized to be involved in review or other regulatory functions; thus, review of adequacy of a) type and extent of investigation, b) conclusions, and c) recommendations is left to local city and county staff who, in many cases, lack sufficient education and/or experience to perform such reviews. California is viewed by many other states as a leader in earthquake awareness and safety. Some states have adopted ordinances similar to the Alquist-Priolo Act which tends to lead the public to believe, “If I am not on the fault, I am earthquake-safe.” This certainly is not the case and regulations such as the Alquist-Priolo Act often are not in the best interest of the public and can promote poor siting decisions. California Assembly Speaker Brown successfully carried a bill (AB 3897) in 1990 requiring the other geologic-related hazards that represent more than 99 percent of the losses to be addressed. Hopefully, this legislation will be implemented and enforced in the future so that the dollar loss from earthquakes can be successfully reduced and life-safety can be better protected. Along with better geologic hazard legislation must be education of the public so that appropriate decisions may be made regarding personal property and life-safety, and wise regulations for public buildings which communities expect to be safe during disastrous events, such as earthquakes.