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It's 2008 — and 'the big one' slams Utah

Published: Wednesday, April 19 2006 3:46 p.m. MDT

A fissure occured in 1934 in Hansell Valley in northwestern Utah.

Deseret Morning News archives

Editor's note: New estimates for what a 7.0 earthquake could do to the

Wasatch Front are scary: It could kill more than 6,000 people, injure 90,000

and cause a $40 billion economic hit. In a five-part series, the Deseret

Morning News describes such a future quake — as if worst-case scenarios

proved to be true.

It is 2 p.m. on Feb. 1, 2008, a freezing, snowy Friday. Most people are still at work or school — which, unfortunately, is the worst-case scenario for what is about to happen.

The next few seconds will release geologic pressure that built over 13 centuries, and — as scientists had predicted back in 2006 — will soon kill 6,200 Utahns, injure 90,000 more, at least moderately damage 42 percent of all local buildings and cause $40 billion in economic losses.

What will long be called the great Utah earthquake of 2008 is hitting the Wasatch fault near Salt Lake City and will measure 7.0 on the Richter scale — a bit smaller than the 7.1 Loma Prieta earthquake near San Francisco in 1989, or the 7.5 that hit Lake Hebgen, Mont., near Yellowstone in 1959.

The coming damage will closely match worst-case predictions made in 2006 (with the aid of a Federal Emergency Management Agency computer program) by Bob Carey, the earthquake director for the state's Office of Emergency Services.

Of course, 2006 was also when Carey and numerous other officials warned that government could not handle such a catastrophe — and said that personal and family preparedness would be the key to how people fare.

Utahns now will find they will need to depend on such preparation for far longer than officials in previous decades had once warned — and may need to survive with their "72-hour" emergency kits for five days or longer.

Police, fire and other emergency responders will be too busy to reach most people for days — so individuals and families will have to rely on themselves and their neighbors for help.

Warnings were correct

Local geologists warned as early as the 1880s that a big earthquake striking the Wasatch Front was not a matter of "if" but "when."

After all, about 700 earthquakes hit Utah every year — including about 13 that are magnitude 3.0 or larger and are felt by residents. University of Utah geologists had said recently that the chance of a large earthquake on the Wasatch Front during the next 50 years is about one in five.

Geologists for years watched stress build along the Wasatch Fault as its adjacent sides — one at the base of the mountain range, the other the beginning of the valley — stretched apart in reaction to earlier, prehistoric compression. For example, recent scientific measurements showed the "valley side" of the fault being stretched to the west by about 2 millimeters a year, or 0.8 inches a decade.

University of Utah seismologist Robert Smith describes such fault stress as being "slowly loaded like a stretched rubber band that suddenly breaks when its strength is exceeded."

Also, earthquakes of about magnitude 7.0 occur on average every 200 to 300 years somewhere on the broad Wasatch Front area, according to Walter Arabasz, director of the University of Utah Seismograph Stations.

He also said they occur on average about once every 1,300 years on the Salt Lake City segment of the Wasatch fault.

When did that last happen? "About 1,300 years ago," Arabasz said back in 2006.

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