In 2011, a megathrust earthquake off the coast of Japan produced a huge tsunami that killed over 15,000 people. The 9.0 magnitude quake was so big it shifted the Earth’s axis and moved the coast of Honshu, Japan’s main island, by 8 feet. Scientists now say a similar earthquake could take place off the coast of Alaska, resulting in a dangerous tsunami that could devastate parts of the state and reach southerly parts of North America, Hawaii and beyond.