Much of the interstate highway system in the Pacific Northwest has been built in the mid to late 1960's. The Washington State Department of Transportation should be consulted for further information about the seismic resistance of individual structures maintained by the state. Many other bridges are under other jurisdictions, but most have been evaluated. That is an individual decision, which depends on the risk that homeowners are financially willing to take. It also depends on their confidence in the quality of their homes, since there is quite a large deductible on most policies.
Some seismologists do have earthquake insurance.
Although scientists have long tried to predict earthquakes, no reliable method has been discovered. Seismicity in the Pacific Northwest has only been extensively studied for a couple of decades, and seismologists are still trying to understand the frequency and hazards of earthquakes in our region. Click Here for a more in depth discussion on earthquake prediction. There is no Seattle area neighborhood that is immune from possible earthquake damage. The age of the structure and the type of geology in the area are two factors that will affect the vulnerability to earthquakes.