There was a very large slide in that region tens of thousands of years ago that almost certainly created a large tsunami. You could say the gas under pressure is being vented so things should be safer now. That's one side of the sword. The other side is the expulsion of the gas has pushed the shelf edge into a mechanically unstable situation and might in fact exacerbate the prospects of future large scale slope failure. A tsunami created by such a landslide could result in waves up to several meters above normal along the Virginia-North Carolina coastline and lower Chesapeake Bay.
Tsunamis can be devastating on populated coastlines.
A tsunami that struck northern Papua, New Guinea in July 1998 killed about 2,000 people. A 1929 tsunami resulting from an earthquake-induced landslide on the Grand Banks killed 51 people along the south coast of Newfoundland. Besides assessing any potential danger from the cracks, the scientists say their research will uncover other information. That includes whether the natural gas offers any economic opportunities. The cracks might also prove interesting to biologists.