QUAKE REPORT BOOSTS DAMAGE ESTIMATE : BAY AREA GROUP FINDS APARTMENT BUILDINGS AT GREATEST SAFETY RISK.

Byline: Frances Dinkelspiel Knight-Ridder Tribune News Wire

A new report drawing on the lessons of the 1994 Northridge Earthquake has determined that a major quake on the Hayward Fault could devastate 150,000 homes and apartment buildings and leave 370,000 people homeless - about three times the numbers previously estimated.

Damage estimates rose dramatically for a major earthquake on the Peninsula section of the San Andreas Fault as well. A 7.0-magnitude quake there would leave an estimated 45,000 homes uninhabitable, according to a new report by the Association of Bay Area Governments.

The report, called ``Shaken Awake

'' and issued last week by the Association of Bay Area Governments, also draws attention to problems plaguing apartment buildings. While most cities and counties have developed programs to retrofit single-family houses built before 1940, multifamily dwellings with garages on the first floor have largely been ignored - and that's where the greatest risk is, according to the report.

``It's not good news,'' said Jeanne B. Perkins, the earthquake program manager for ABAG and one of the report's authors. ``Having looked at Northridge we have a much more pessimistic outlook on the habitability of apartments built in the '60s, '70s, '80s, '90s after an earthquake.''

The report is intended to prompt cities and counties to re-examine their building codes and seismic retrofitting plans, as well as to encourage homeowners to strengthen their residences, Perkins said.

ABAG also wanted to provide specific numbers to the American Red Cross and other community organizations to help them plan for the thousands of people who will seek public shelter after an earthquake. If a 7.3 temblor ruptures the length of the Hayward Fault from San Pablo Bay in the north to San Jose in the south, as many as 107,000 people - the size of the city of Berkeley - won't have friends and relatives to turn to and will need to sleep in schools and community buildings, according to the report. The bulk of them will probably be low-income and have few resources.

Those numbers, while staggering, were no surprise to officials involved in emergency planning. American Red Cross officials, for example, have estimated 135,000 people will need shelter after a major quake on the Hayward Fault, according to Doug Sandy, the assistant director for the Bay Area American Red Cross.

``We sit in one of the highest disaster risk areas of the country,'' Sandy said.

``Loma Prieta was not our earthquake,'' agreed Henry Renteria, emergency services manager for the Oakland Fire Department. ``The Hayward Fault has not yet produced the earthquake we are waiting for.''

The report was an update of a 1992 ABAG report - but this time the results were more sobering. In the earlier assessment, the agency concluded that a major earthquake would severely damage 57,000 homes and apartments.

The ABAG report provided 11 other earthquake scenarios. Six of the scenarios are estimated to have greater impact on the Bay Area's 2 million living units than the Loma Prieta Earthquake.

If both sections of the Hayward Fault ruptured, 150,000 dwellings would be so severely damaged that no one could live in them. About 82,500 of those units would be in Alameda County, 38,700 would be in San Francisco, 13,400 would be in Santa Clara County, 9,600 would be in Contra Costa County, and 1,600 would be in San Mateo County.

If a large earthquake hits the Peninsula segment of the San Andreas Fault, about 45,000 homes and apartments will be uninhabitable. About 9,000 of those would be in Santa Clara County, 13,000 in San Mateo County, 19,000 in San Francisco, and 3,000 in Alameda County, with the rest of the damage in other areas.

That was a significantly greater estimate than in the 1992 report, which estimated a 7.0-magnitude quake on that section of the San Andreas Fault would leave only 8,200 red-tagged units in its wake, mostly in San Francisco, San Mateo and Santa Clara counties.

For the new report, ABAG used more sophisticated ground shaking models developed in 1995 and information already gleaned from census data and housing inventories in nine Bay Area counties. Researchers also inventoried which buildings were ``red-tagged or ``yellow-tagged'' - meaning they were uninhabitable - during the 1989 Loma Prieta and 1994 Northridge earthquakes. They also interviewed many of those left homeless in the Los Angeles temblor to determine the demographic characteristics of those seeking shelter.

Some cities and counties are already using the information developed by ABAG. Santa Clara County, for instance, recently inventoried its stock of apartments and determined that half the three- to-four-story buildings have ``soft'' first floors, leaving them vulnerable to collapse during a strong earthquake, Perkins said.

San Jose is developing a program to address retrofitting those buildings, according to Frannie Winslow, the director of emergency preparedness for San Jose who also served as an adviser for the ABAG report. The city is working with the Tri-County Apartment Association to develop a public education program for building owners - a first step toward making them safer, she said.

The ABAG report, as well as detailed maps and charts that lay out each county's specific risks can be accessed on the World Wide Web. The address is http://www.abag.ca.gov.

ABAG is also selling a CD-ROM called ``On Shaky Ground,'' with more than 1,000 full-color maps depicting earthquake shaking hazards, dozens of photographs and more than 30 minutes of video. The CD-ROM may be purchased for $40 by mail from ABAG Publications, P.O. Box 2050, Oakland, CA 94604.