Experts survey the National Mall for sinkage

Hank Silverberg,

WASHINGTON – Experts are trying to determine whether the National Mall and the nation’s monuments are sinking and whether the August earthquake made it worse.

Scientists from the National Oceanic and Atmospheric Administration are surveying the area around the Washington Monument which was damaged during the Aug. 23, 2011 quake.

“Whatever changes that have gone on, they do appear to be very, very minor,” says Dave Doyle, the chief surveyor for NOAA’S National Geodetic Survey.

“We are all thankful for that, but we really needed to get in there and prove that,” he says.

Much of the National Mall is built on landfill and previous surveys over the years have indicated the land has sunk more than two inches since the monument was finished in 1884.

Doyle says the quake may have shaken things up.

“The effect of the event, the earthquake of last August, can cause the issue of what’s often referred to as liquefaction, which kind of shakes up all the stuff that’s underneath it,” he says.

There was about a millimeter of that, Doyle says.

There are preliminary indications the quake did not cause significant vertical motion for the monument.

Even slight changes could impact the $15 million project to repair the monument.

The survey team also will be checking around the other monuments as well measuring them against more stable benchmarks around the Capitol Building.

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(Copyright 2012 by WTOP. All Rights Reserved.)

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