2. Determine the Safety of Your Home or School

Most people in California are safe at home if they live in a one- or two-story wood-frame building. These buildings are not likely to collapse during earthquakes. The most common damage is light cracking of interior walls, cracking of brick chimneys, and cracking and possible collapse of brick veneer on exterior walls. A cracked chimney should be inspected by a qualified professional before the fireplace is used.

Unfortunately, some one- or two-story wood-frame buildings can be hazardous. Those built before about 1940 can fail at or near ground level if they are not adequately bolted to the foundation or if the short "cripple" walls, often found between the foundation and the first floor, are not adequately braced. Information on adding foundation bolts and bracing cripple walls is available through your local Office of Emergency Services. Correcting these two problems will drastically reduce the earthquake risk for residents in older homes. Bracing of chimneys in older homes may be required to prevent toppling during earthquakes.

Modern public elementary and high schools and community college buildings have generally performed well during earthquakes. Following severe damage to many schools during the Long Beach earthquake of 1933, the Field Act was passed, requiring special seismic design for public school buildings. However, knowledge about proper seismic design has increased dramatically since then. Older school buildings may need to be reassessed in light of modern building codes.

The provisions of the Field Act do not apply to colleges and private schools. Ask school officials whether the school buildings have been recently evaluated for earthquake resistance.

Bolting the wood frame of an older house to the concrete foundation can significantly reduce earthquake damage. Every 3 to 4 feet along the foundation, drill a hole using a right-angle drill with a 1/2-inch bit (A), blow the concrete powder out of the hole with a small piece of flexible tubing (B), and hammer in an expansion bolt, 1/2-inch in dia-meter and about 5-1/2-inches in length (C). Tighten the nut on the expansion bolt.

Mobile homes, portable classrooms, and modular buildings can slide off their foundations during earthquakes. Their supports need to be braced to resist horizontal forces. If portable classrooms are used at your local school, you should ask school officials whether they are properly braced.

Reinforcing the 'cripple' walls between the foundation and first floor of an older, wood-frame house can significantly reduce earthquake damage. Nail 2 by 4 inch blocks of wood to the mud sill as needed (A). Cut 1/2-inch plywood to fit the inner side of the wall (B). Fasten plywood along all edges and to each stud using 8d nails spaced 3 inches apart.