Eh, it's a bit over-simplified. It's different times for each segment; I was referring to the central segments immediately around SLC.
http://geology.utah.gov/online/pdf/pi-40.pdf
"These earthquakes took place on the fault's five central segments (Brigham City, Weber, Salt Lake City, Provo, and Nephi) and one distal segment (Levan). Collectively, the "composite recurrence interval," or how often a large earthquake has occurred on the central portion of the Wasatch fault, is approximately once every 350 years. The last large earthquake happened about 600 years ago on the Provo segment, and possibly earlier on the Nephi segment (although the starburst position indicates a carbon-dated event closer to 1,200 years ago, some researchers estimate an earthquake occurred as recently as 400 years ago on the Nephi segment)."
A PDF unfortunately...
A non-pdf:
http://www.journalnet.com/articles/2003/09/14/news/local/news11.txt
"Simple timing underscores why geologists are putting a target on Salt Lake City: The Wasatch fault here last slipped with a violent shudder about 1,283 years ago - and the intervals between each of the four most recent prehistoric quakes ranged from 1,269 to 1,441 years.
All dates are qualified by different margins of error, but the implication is clear.
"The earthquake strain has been accumulating all this time and there is sufficient energy to release the big one," said Walter Arabasz, director of the University of Utah's Seismograph Stations.
"What's overdue is strong shaking. Since 1847 we've just been lucky," he said.
A magnitude 7.5 quake could kill 7,600 people in the Salt Lake basin, injure 44,000 others and cause $12 billion in building damage alone, a pair of Stanford University engineers calculated in 1994.
The main Wasatch fault, which snakes along the base of the Wasatch Range, isn't the only threat to Utah's largest city. Out on the basin floor, the West Valley fault group also is poised to release a powerful quake.
Over the past 12,000 years, the West Valley complex produced a powerful jolt every 1,700 to 2,000 years - most recently about 2,000 years ago, geologist Jeffrey Keaton determined."