On 22 May 1960, offshore the south coast of Chile, occurred the strongest earthquake of the 20th century, M.9.5 (the highest earthquake instrumentally detected), followed by a powerful tsunami, up to 25 meters waves run up (excluding tide) on the coast of Isla Mocha, Chile, near the epicenter.
Tsunami reached the coasts of the entire Pacific Ocean.
It reached Hawaii after about 15 hours, waves over 10 meters of run up; in New Zealand the waves peaked between 5 and 10 meters high and, after about 22 hours, the tsunami hit the coasts of Japan.
Changes in sea level caused by the tsunami were also recorded by British mareograph, from Bermuda to South Africa and Australia, making this the first global tsunami.
The magnitude of the Valdivia tsunami gave a new impulse to the studies and implementation of tsunami early warning systems. Just think of the case of Japan where: nobody felt the shake of the earthquake (there are more than 17,000 km of ocean between the two nations) and the JMA did not give the alert, however, the tsunami waves generated by the earthquake traveled for many hours throughout the Pacific, and their arrival on the Japanese coast the next morning, with heights between 3 and 6 meters, took the inhabitants totally unawares, causing huge economic damage.