The Pacific Ocean is one of Earth's seas and the overall largest sea on the planet.
Los Angeles Earthquake
Near the Japanese seaboard, the Genesis ship was hit by a gigantic tsunami when the Worldwide Flooding occurred in the Pacific. Asia was now at the Pacific Ocean's original position, which allowed the Curtis and Karpov group to land in Cho Ming Valley when they were heading for the Arks.
After the apocalypse ended, the new position of the Pacific Ocean continued to remain in its current position when the Arks set sail for the risen continent of Africa (which did not suffer extreme damage)