Liquefaction

From the hills in Yorba Linda to the tract homes along Serrano Creek in Lake Forest, vast chunks of Orange County could be damaged by liquefaction or landslides in a 5.5 magnitude earthquake or larger, state officials said Tuesday. Maps of three areas of Orange County pinpoint danger spots in eight communities, areas where the soil under homes could be turned to quicksand and where hillsides--even those as modest as the slopes near UC Irvine--could give way in landslides.

Most of downtown Ventura could be at risk of liquefaction during a major earthquake, while landslides could be a danger in the hills above the city, according to a seismic hazards map issued by state geologists this week. The liquefaction zone stretches from the ocean to the area north of Poli Street. Liquefaction occurs when sandy soil becomes saturated by ground water and then is shaken. It is the 20th of 21 state maps to be released for the county.

State geologists released the first seismic hazard maps for parts of Orange County on Tuesday under a new program requiring geologic investigations and mitigation measures for new building projects in zones subject to ground liquefaction in big quakes. Once the maps become official in about six months, homeowners in a seismically hazardous zone who sell their properties will be required to disclose the potential danger to buyers.

Most of downtown Ventura could be at risk of liquefaction during a major earthquake, while landslides could be a danger in the hills above the city, according to a seismic hazards map issued by state geologists this week. The liquefaction zone stretches from the ocean to the area north of Poli Street. Liquefaction occurs when sandy soil becomes saturated by ground water and then is shaken.

Most of downtown Ventura could be at risk of liquefaction during a major earthquake, while landslides could be a danger in the hills above the city, according to a seismic hazards map issued by state geologists this week. The liquefaction zone stretches from the ocean to the area north of Poli Street. Liquefaction occurs when sandy soil becomes saturated by ground water and then is shaken.

State geologists released the first seismic hazard maps for Topanga Canyon and a segment of the San Fernando Valley on Tuesday under a program requiring geologic investigations and mitigation measures for new building projects in zones of ground liquefaction and landslides in big quakes. Homeowners who sell their properties will also be required to notify buyers that they are moving into a seismically hazardous zone once the maps become official in about six months.

Most of downtown Ventura could be at risk of liquefaction during a major earthquake, while landslides could be a danger in the hills above the city, according to a seismic hazards map issued by state geologists this week. The liquefaction zone stretches from the ocean to the area north of Poli Street. Liquefaction occurs when sandy soil becomes saturated by ground water and then is shaken. It is the 20th of 21 state maps to be released for the county.

Homes throughout south Orange County could be heavily damaged by liquefaction or landslides in a major earthquake, according to maps released Thursday by the state Department of Conservation. The maps are part of an ongoing project to identify seismic hazards throughout California. Similar maps pinpointing seismic risks have already been released for most of the rest of Orange County.

Regarding the recycling of water in the San Fernando Valley as discussed in the Dec. 5 Times, it certainly makes sense from a conservation point of view. However, when considering earthquake safety measures, the recycled water increases the liquefaction potential in the Valley, resulting in significantly increased damage potential during earthquakes there. Thus it seems more appropriate to allow water recycling in geologically less sensitive areas, but refrain from doing it in the Valley.

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.

Homes throughout south Orange County could be heavily damaged by liquefaction or landslides in a major earthquake, according to maps released Thursday by the state Department of Conservation. The maps, which cover 120 square miles, identify dangers in the event of a magnitude 6.0 or greater earthquake in Aliso Viejo, Dana Point, Irvine, Laguna Beach, Laguna Hills, Laguna Niguel, Mission Viejo, Rancho Santa Margarita, San Clemente and San Juan Capistrano.

Homes throughout south Orange County could be heavily damaged by liquefaction or landslides in a major earthquake, according to maps released Thursday by the state Department of Conservation. The maps are part of an ongoing project to identify seismic hazards throughout California. Similar maps pinpointing seismic risks have already been released for most of the rest of Orange County.

From the hills in Yorba Linda to the tract homes along Serrano Creek in Lake Forest, vast chunks of Orange County could be damaged by liquefaction or landslides in a 5.5 magnitude earthquake or larger, state officials said Tuesday. Maps of three areas of Orange County pinpoint danger spots in eight communities, areas where the soil under homes could be turned to quicksand and where hillsides--even those as modest as the slopes near UC Irvine--could give way in landslides.

At least a third of Orange County lies atop soil susceptible either to earthquake-induced landslides or liquefaction, according to the latest version of an ongoing seismic mapping study by the state Department of Conservation. Landslides, as well as liquefaction--in which loosely compacted, moist earth gives way after jarring from an earthquake--typically account for a substantial portion of the secondary damage from earthquakes.

Maps showing areas in Los Angeles and Orange counties where earthquake damage is most likely to be exacerbated by soil liquefaction were released Thursday by the state Department of Conservation. The 24 maps, which cover about 2,600 square miles in 83 cities, are intended for use when planning new structures or selling existing ones, said state geologist James Davis.

In the ranks of those fearing that doom is at hand, homeowners in the San Fernando Valley stand somewhere between Apple stockholders and the Michigan Militia. When government and business try to alter policy or develop land, residents tend to assume it is all an unmitigated assault on their property values. The Valley is NIMBY central. Often, those on the receiving end of their protective wrath shrink away in defeat. But not Mother Nature.

Seismic hazard maps showing areas in which homeowners will be required to report quake danger to potential buyers were issued Friday covering 300 square miles of the San Fernando and Santa Clarita valleys. The maps issued by the state Department of Conservation show nonhazardous areas generally north of Vanowen Street and hazardous areas to the south.

A major earthquake in the central United States will give some soils the consistency of quicksand, toppling even many quake-resistant buildings, officials said Wednesday. E. Erie Jones, executive director of the Central United States Earthquake Consortium, a seven-state disaster preparedness agency, urged that building codes and land-use regulations be changed to prepare for the liquefaction risks in an earthquake.

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.

Seismic hazard maps showing areas in which homeowners will be required to report quake danger to potential buyers were issued Friday covering 300 square miles of the San Fernando and Santa Clarita valleys. The maps issued by the state Department of Conservation show nonhazardous areas generally north of Vanowen Street and hazardous areas to the south.