Large earthquakes along the Eastern Seaboard are very uncommon (but they do happen from time to time … Charleston S.C. in 1886 and Boston in 1755), making the threat of an earthquake-spawned ocean wave minimal. But that doesn’t mean the danger should be discounted. Tsunamis have hit the East Coast in the past. Philadelphia and the Delaware River (1817, 1884), Long Island (1895, 1871) and other places have seen tsunamis, though destruction was minimal compared…