Carey said he also would expect some water and sewer lines to be knocked out because the lines tend to be brittle and break with shaking. He adds he would expect some power blackouts. "Power is pretty delicate," he said. "If it does go down, they'll leave it down for a time to make sure they don't damage it by bringing it back up."

He said some liquefaction — or soils acting like liquids, or quicksand, where structures may tip over — is possible with a 6.0.

"A lot of that depends on the duration of the event," he said. "If you see it, you'll likely see it along someplace like the Jordan River — so you could have some problems with bridges crossing the Jordan (River)."

Carey also notes that a 6.0 would have been big enough to cause major damage to some buildings before recent seismic retrofitting. "If a 6.0 hit the state Capitol before its retrofit, it would have caused major damage to the dome. Now, I expect it would cause no problem."

Still, all of the damage expected from a 6.0 is only considered moderate, Carey said, and local governments could probably handle all needed response, with assistance from emergency officials on the edge of the quake-affected area.

That would not hold true with a large quake, such as 7.0.

Carey said computer modeling done two years ago — and reported by a 2006 Deseret Morning News series — predicted a worst-case 7.0 in Salt Lake County could kill 6,200 people, injure 90,000 more, at least moderately damage 42 percent of all local buildings and cause $40 billion in economic losses.

Carey said the only change in those numbers in two years is that because the population has increased, "we might expect even more casualties."

It would swamp emergency responders, and many would need to depend on neighbors, community emergency training and their emergency supplies for survival for five days or longer.

A 7.0 releases 32 times more energy than a 6.0, and creates 10 times more ground shaking, Carey said.

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Contributing: Arthur Raymond
E-mail: lee@desnews.com