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The earthquake triggered extremely destructive tsunami waves of up to 10 meters (33 ft) that struck Japan minutes after the quake, in some cases traveling up to 10 km (6 mi) inland,[10] with smaller waves reaching many other countries after several hours. Tsunami warnings were issued and evacuations ordered along Japan's Pacific coast and at least 20 other countries, including the entire Pacific coast of North America and South America

One minute prior to the effects of the earthquake being felt in Tokyo, the Earthquake Early Warning system, which is connected to more than 1,000 seismometers in Japan, sent out warnings of an impending earthquake to millions. This was possible because the damaging seismic S-waves, traveling at 4 km (2.5 mi) per second, took about 90 seconds to travel the 373 km (232 mi) to Tokyo. The early warning is believed by the JMA to have saved many lives

The quake moved portions of northeast Japan by as much as 2.4 meters (7.9 ft) closer to North America,[20][21] making portions of Japan's landmass "wider than before," according to geophysicist Ross Stein.[21] Portions of Japan closest to the epicenter experienced the largest shifts.[21] Stein also noted that a 400-kilometer (250 mi) stretch of coastline dropped vertically by 0.6 m (2.0 ft), allowing the tsunami to travel farther and faster onto land.[21] The Pacific plate itself may have moved westwards by up to 20 m (66 ft), though the actual displacement will have diminished with greater distance from the site of the fault.[46] Other estimates put the amount of slippage at as much as 40 m (130 ft), covering an area some 300 to 400 km (190 to 250 mi) long by 100 km (62 mi) wide. If confirmed, this would be one of the largest recorded fault movements to have been associated with an earthquake.[