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Big quake rattled Utah 500 years ago, next could strike at any time

Big quake rattled Utah 500 years ago, next could strike at any time



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SALT LAKE CITY -- The Utah Geological Survey has been busy digging holes, trying to find more information on the frequency of large past earthquakes along the Wasatch Fault Line.

After digging a trench near North Ogden, Geologists recently discovered evidence of a major earthquake that struck the area nearly 500 years ago. They also found evidence of six other earthquakes of a magnitude 6.5 or greater that seem to be spaced about 1,500 years apart.

Geologist Chis DuRoss with the Utah Geological Survey says this shows the fault continues to be active, and they didn't know about the quake 500 years ago.

"Looking at the length of this part of the fault which is about 35 miles and the amount of movement of the ground surface, we think this would be about a magnitude 7 earthquake, so certainly devastating for the Wasatch front," said DuRoss.

So when will the next big earthquake strike the Wasatch Front metro area? "When we look at the most active part of the fault, these earthquakes occur about every 300 years. The most recent large earthquake on the Wasatch Fault occurred about 350 years ago near Nephi," said DuRoss.

The entire Wasatch Fault runs from Southern Idaho to Levan, but the most active areas are between Brigham City and Nephi.

Overall, DuRoss says a large earthquake is due. "So in the Wasatch the safe thing to say is that one of these earthquakes could occur at any time," he said.

Geologists say an earthquake with a magnitude 6.5 or higher would cause major destruction in the metro areas of Utah, especially to brick buildings built before 1975 that are not reinforced.

DuRoss says they are hoping to excavate trenches next spring in the Salt Lake City part of the fault near the University of Utah.

The fault runs along the range front near Big and Little Cottonwood Canyons and then jumps out at about 4500 South. From there, it heads towards Highland Drive to about 1300 East. It then passes the University of Utah campus and heads west toward downtown, but DuRoss says they aren't sure where the trace of the fault goes through downtown because of the development.

E-mail: rjeppesen@ksl.com

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Randall Jeppesen

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