Fellow Blogista Dennis Bryant warns: “There are unofficial reports that the 8.8 magnitude earthquake that struck Chile last month has moved parts of the nation. The city of Conception may have moved as much as ten feet to the west, while Santiago may have moved eleven inches to the west-southwest. Even areas outside Chile, including the Falkland Islands and Brazil, may have been affected. As yet, there are no reports of elevation changes, but mariners navigating waters in and around Chile should exercise caution until definitive new surveys are done. The 1964 earthquake in Alaska caused significant elevation changes, particularly at Kodiak Island, and resulted in a number of groundings until charts could be updated.”
It’s worth remembering that earthquake can, and do, change seabed profiles significantly enough to invalidate chart data. This will happen more often in geologically unstable areas such as on the Pacific Ring of Fire.