A University of Washington researcher says an earthquake on the Seattle fault would be even more devastating if it occurs when the land is saturated with rain.
Research by Kate Allstadt indicates a quake in dry weather would trigger about 5,000 slides in the city, but 30,000 if the soil is wet.
The Seattle Times reports more than 10,000 buildings are at risk in the worst-case scenario, many of them upscale homes with water views on bluffs or hills.
The last quake on the Seattle fault about 1,100 years ago was estimated at 7.5 and caused a forest to slide into what is now Lake Washington.
A report on Allstadt's study was published this month in the Bulletin of the Seismological Society of America.