Is there any case that changed from earthquake safe zone to danger zone?
Yes, prior to 1983, central Idaho was classified low to moderate.  On October 28, 1983,  a  powerful earthquake occurred in Lost River Range at Borah Peak in central Idaho. The shock measured 6.9 on the moment magnitude scale and had a maximum Mercalli intensity of IX (Violent).

The earthquake was centered only 50 miles from a Idaho National Engineering Lab (nuclear research laboratory), but no damage was reported a the site. 

Unfortunately, I can't find an internet accessible report but I remember discussing this earthquake at length in a Engineering Geology class I was taking in 1986.  The magnitude of the Borah Peak surprised the US government prompted the USGS to reclassify earthquake hazard zones in Idaho and Utah.

Location of Borah Peak, Idaho.


Current quake hazard map (from USGS:) 


References:


Wikipedia Borah Peak. 
New York Times article on quake
Geological summary of the quake: Idaho State University By, Steven W. Moore, Geologist and R. David Hovland, Geologist: