Quake Maps Fail to List All Hazards

The latest in a series of seismic hazard maps--covering 300 square miles that include virtually all of the San Fernando and Santa Clarita valleys--were issued by the state Friday in a move toward establishing new land use controls.

But as with earlier maps issued for parts of Orange County and Simi Valley, a major question is why not all quake hazards are covered.

When they become official in six months, the maps issued by the state Department of Conservation will trigger requirements that builders of duplexes and apartment houses prepare seismic hazard reports and plans for reducing the dangers before they build.

Owners of all dwellings within the zones designated as hazardous, including single-family homes, will have to disclose that status to buyers when they sell their properties. But the hazards covered by the maps include only earthquake-induced liquefaction and landslides, ignoring shaking hazards.

Homes in the epicentral, and often the most heavily damaged, areas of the 1971 Sylmar-San Fernando and the 1994 Northridge quakes are in areas not designated as hazardous in the new maps. This means that property in those areas will not be subject to the new requirements, despite two devastating quakes within a quarter-century.

State officials said Friday that there is no timetable for preparing maps that will include shaking hazards.

The maps are being issued pursuant to legislation adopted after the 1989 Loma Prieta earthquake induced liquefaction that severely damaged the Marina district of San Francisco.

Liquefaction is a process in which water-saturated soils turn jelly-like under heavy shaking.

The latest maps show danger of liquefaction in areas beside the Los Angeles River, which flows from west to east across the Valley.

Maps for the rest of Los Angeles will be issued next year.