Just off the west coast of Vancouver Island lies the convergence point of three tectonic plates: the Juan de Fuca plate from the south, the Explorer plate from the north and the North American plate to the east. When a 6.8 magnitude earthquake began to rumble 30 miles below Olympia, Washington on February 28, 2001, Bill Gates was on a stage in downtown Seattle, telling hundreds of people about the benefits of XP software. The stage began trembling, but Gates remained calm.

When he returned to the podium, he said, "OK, so where was I?"

An audience member shouted back: "You said you had an earth-shattering announcement to make!" *

Bill Gates had the good fortune to be standing inside an earthquake resistant building but many people in Washington and British Columbia were not as lucky. The quake lasted only 40 seconds but the damage to buildings, bridges and roads cost untold millions.

Just off the west coast of Vancouver Island lies the convergence point of three tectonic plates: the Juan de Fuca plate from the south, the Explorer plate from the north and the North American plate to the east.

Although the Pacific seaboard has a reputation for being earthquake prone, there is no place on earth that is immune to possibility of an earthquake. There are eight major plates and many minor plates that are constantly moving, very slowly over the surface of the earth. As these plates move, stresses build up in areas where the plates come into contact with each other. Within seconds, an earthquake releases stress that has slowly accumulated.

A US Geological Survey map of seismic activity from 1999-2000 shows hundreds of earthquakes all across Canada. The largest concentrations are on the Pacific coast as well as Ontario and Quebec. All provinces with the exception of Newfoundland experienced seismic activity during this two-year period.

The question many caution homeowners may be asking is: "Is my home earthquake safe?" If you are not asking that question, consider the extent of the damage in Japan, a country that is highly prepared: 45,000 people were still living in temporary shelters five years after the Kobe earthquake.

In this country, many homes, particularly older homes, were constructed to withstand the force of gravity and the weight of contents. However, an earthquake produces a lateral load, basically shaking a home from side to side. You may remember the egg board commercials showing a farmer pressing down hard end-to-end on an egg without breaking it. Of course, make a slight tap to the side of an egg and you have an omelette!

A report released by the Canadian Housing and Mortgage Corporation (CHMC) in 1999 assessed the ability of different building styles to withstand an earthquake. The study involved housing in Vancouver, which although not identical to building styles in the rest of Canada, may serve as a good general guideline. The destruction of buildings in a major earthquake were estimated as follows: single family wood frame homes: 10 - 30%, un-reinforced masonry homes: 50 - 100%, low - and medium-rise buildings: 20 - 30% and high-rise residential: 10 - 20%.

If you decide to reinforce your home to make it more earthquake resistant consider these three common problems areas:

Cripple Wall Failure

Cripple walls are the short-framed walls that extend from the top of the foundation to the base of the floor structure. These walls are common in older wood-frame houses with crawl spaces. The walls are typically built with vertical 2X4 studs. Un-reinforced cripple walls are a weak link between the lower floor and the foundation.

The addition of plywood sheets, known as shear panels, nailed to the cripple walls can help prevent collapse during lateral seismic shaking.

Sliding Off the Foundation

When a home is not securely attached to its foundation there is a risk that the home will actually slide off. During an earthquake, the foundation typically begins to oscillate before the roof even starts to move. The result is the top and bottom edges of the walls can shear or move horizontally past each other. The walls may crack or even collapse.

To help deal with this problem, use anchor bolts to attach the wood frame (or sills) to the concrete foundation. If your home is already bolted in place, you may want to consider an inspection to determine if the bolts are adequate.

'Soft Story' Collapse

Many homes and commercial buildings have what is called a "soft story" condition. This term is used to describe any building that has a habitable room or rooms above a garage, carport, or porch area that was not specifically designed to transmit shear or lateral forces to the story above.

These makeshift living areas should be reinforced with a steel frame, which can absorb some of the lateral force of an earthquake.

Other Home Styles

Owners of post and beam construction homes may want to take the precaution of reinforcing joints with plywood gussets or T-straps to ensure against separation or displacement.

CMHC has developed a video called 'Is your home earthquake resistant?' for homeowners and published a 150-page Residential Guide to Earthquake Resistance for builders and renovators. To find out more about these resources please visit http://www.cmhc-schl.gc.ca

* based on a report in the Seattle Post-Intelligencer March 1, 2001