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SALT LAKE CITY — Geologist Adam McKean said experts knew there were some faults in the earth west of the Salt Lake International Airport.
"I would easily walk across this area without knowing there was a fault," McKean said.
But with traditional geology tools, previous geologists couldn't map them correctly.
"You don't see a ledge or a cliff or a crack like you would normally expect on a geologic fault,” McKean said.
Now, geologists know there are fault lines in the Salt Lake City area.
“If your building was across this and it faulted, it would be bad. Your structure would collapse," McKean said.
A thin cover of vegetation is the reason the fault isn't apparent even to an expert's eye — or to many instruments. But an imaging technique called LIDAR almost literally strips the greenery away: “The LIDAR is really fantastic,” McKean said.
LIDAR is a lot like radar, except with lasers instead of radio waves.
A LIDAR unit mounted on an airplane shoots out millions of laser pulses, blanketing the landscape with tiny light beams. The LIDAR catches the light that bounces back. Just enough of the laser beams shoot through the vegetation and reflect back. That allows LIDAR computer processors to paint images of a landscape denuded of trees, shrubs, grass and even some lighter buildings.
If there's a grove of trees, we can see right through that grove of trees and see the ground underneath.
–Gregg Beukelman, the Utah Geological Survey
LIDAR imagery removes the vegetation to reveal drainage patterns. Experts can map drainage channels and discover other clues for potential runoff and flooding problems.
"It lets us see things that are so small, in so much detail, that otherwise we wouldn’t know about," McKean said.
In City Creek Canyon the LIDAR technology has been extremely valuable in helping geologists map old landslides, some of which they never knew were there.
“So that's actually got a name (pointing to a hillside in City Creek Canyon) — The City Creek Landslide,” Gregg Beukelman from the Utah Geological Survey said.
Geologists knew about this trouble spot because it slides just about every time a wet year comes along.
But many old landslides remained hidden by vegetation, on slopes that have homes on top of them, and once again LIDAR has technology paid off.
“If there's a grove of trees, we can see right through that grove of trees and see the ground underneath,” Beukelman said.
This technology has allowed geologists to map several hidden landslides.
“There's clear evidence of lots of landslides here, yes, and that's why the LIDAR technology has become hugely valuable,” Beukelman said.
When one landslide happens there could easily be future landslides for experts, planners and yes, even homeowners.
Contributing: Sara Jarman
