The U.S. Monument suffered cracks in 1884 's earthquake . The monument has sunk nearly 2 inches since its completion in August . NGS surveyors and the National Park Service are investigating whether the August 23 , 2011 , earthquake caused the 555-foot stone obelisk to sink or shift . Rubenstein will also look at other monuments in the capital .
The U.S. Monument suffered cracks in 1884 's earthquake . The monument has sunk nearly 2 inches since its completion in August . Rubenstein will also look at other monuments in the capital .