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Geologists examine Salt Lake City portion of Wasatch Fault

By John Hollenhorst | Posted - May 26, 2010 at 4:49 p.m.


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FEDERAL HEIGHTS -- Scientists are getting the first good look they've ever had at the Salt Lake City portion of the Wasatch Fault. What they've seen so far confirms a major earthquake is a constant threat.

In fact, geologists dug two big trenches in a vacant lot right next door to the University of Utah's president's mansion.

For the last two and a half weeks, they've had an unprecedented opportunity to look at the guts of the Wasatch Fault in this area. They've dug similar trenches elsewhere, but until now, the closest was in the Sandy-Draper area.

As expected, there's evidence of at least six major earthquakes averaging about once every 1,300 years. The last one hit roughly 1,300 years ago.

What is... the Wasatch Fault?
The Wasatch fault is 240 miles long stretching from southern Idaho, through Utah, into northern Arizona. It is made up of several segments, which, on average, measure some 25 miles long.

Geologists hope the excavation will help pin down the dates and refine their understanding of the earthquake threat.

"This trench, just like other trenches on the Wasatch Fault, show that the fault is very active," said Chris Duross with the Utah Geological Survey. "It's important for folks to understand that the fault is active and that we could expect an earthquake at any time. The bottom line is that the entire valley would be shaken very strongly."

![](http://media.bonnint.net/slc/2072/207237/20723757.jpg) Wasatch Fault through Salt Lake Valley, Courtesy USGS
Over the last couple of weeks, the geologists have taken lots of samples, measurements and pictures. They'll have plenty of data to study after they fill the trenches back in Thursday.

Excavating in that particular area was a rare opportunity, because for many years, the fault has been pretty much covered by homes and other developments.

The vacant lot is owned by Ian and Annette Cumming. They gave permission for the excavation to help scientists get a better handle on Utah's seismic future.

E-mail: hollenhorst@ksl.com

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