The recent Napa earthquake caused significant damage to buildings in the historic downtown areas of the cities of Napa and Vallejo, and brought to the fore the limited extent to which California law requires seismic safety upgrades to unreinforced masonry buildings and other structures that were built before current building code requirements became applicable. Unlike many earthquake related disasters in other countries, where collapses of recently built structures with great loss of life and property damage are often attributable to lax, outdated building codes, corruption of building inspectors, or other failures of current building regulations, in California the most severe earthquake damage usually occurs in older buildings constructed long before current structural and seismic safety code requirements were imposed. As outlined in this article, land use planning for new projects is required to take into account earthquake and seismic safety criteria, and the State’s construction and building codes directly impose seismic safety techniques in the design and construction of new buildings and in substantial alterations and additions to those structures. As to other preexisting structures, however, several laws enacted after major seismic events have appeared to address those issues, but for the most part leave to local agencies the determination of how, if at all, seismic retrofit or seismic upgrade requirements will apply to existing structures. Many jurisdictions have not imposed rigorous retrofit requirements on owners of existing buildings known to be seismically at risk.

I. Seismic Safety Requirements and Planning for New Projects Under the Alquist Priolo Act and the Seismic Hazards Mapping Act.

Overview of the statutes. The Alquist-Priolo Earthquake Fault Zoning Act and the related Seismic Hazards Mapping Act impose geotechnical and seismic mapping requirements for the approval of all new construction projects that are located in seismic hazard areas, and for the mapping and dissemination of information concerning such zones. The Alquist-Priolo Act requires the State Geologist to develop and compile maps delineating earthquake fault zones and includes requirements for project approval in accordance with policies and requirements of the State Mining and Geology Board. The Seismic Hazards Mapping Act provides for the mapping of other seismic hazard areas including those areas that may be affected by strong ground shaking, liquefaction, landslides, and other ground failure in the event of an earthquake, as well as the provision of such maps to cities and counties by the State Geologist for use in the planning, zoning, and project approval processes for such areas in the jurisdiction.