You might be referring to the aftermath of the Chesapeake Bay Impact Crater, which is one of the largest craters to have struct Earth.

The crater is classified as a complex crater and as a result of the impact, the asteroid left a "W" imprint in the surface. The land on the outskirts of the crater(The "W") is unstable and is most likely what is calling the region around Norfolk to sink.

Someone with more geology knowledge might have more to say about it however :)