A good resource is Oregon HazVu, DOGAMI's interactive web map for viewing information about earthquake, landslide, flood and other hazards: http://www.oregongeology.org/sub/hazvu/
HazVu is intended to provide a starting place for learning about geologic hazards, and to help you determine whether you might need to hire a geotechnical professional to evaluate your property. HazVu includes the best available DOGAMI data, but mapping may not be complete for all hazards in all areas.