The Washington Transportation Department says the elevated highway along the waterfront is safe, but vulnerable in an earthquake.
A routine inspection was conducted the weekend of March 1-2 and discovered new and widening cracks near Spring and Seneca streets.
The department said Monday the cracks are a half-mile north of - and unrelated to - the machine drilling the Highway 99 replacement tunnel.
Spokesman Travis Phelps says no new settling was measured. The viaduct has been regularly inspected since the 2001 Nisqually earthquake and it has settled more than 5 inches at one spot near Yesler Way.
The department plans to close the viaduct again on Saturday March 22 for a follow-up inspection.