Most Portlanders are aware that we live in a seismically active region. But many people are not aware that older homes built prior to 1960 are not bolted down to their foundations. Such a house would be much more dangerous to both inhabitants and property than one that was secured. There are several companies in town that specialize in seismic strengthening- and you can do so without breaking the bank. While you are at it, perhaps you should add earthquake insurance to your policy- at very little cost it could provide a lot of piece of mind.
You can seismically upgrade yourself, and whether you choose that route or opt to oversee your contractor from an informed position, here's a link to what is involved from Portland Bureau of Development Services.