As a tsunami approaches shore, we’ve learned in the “What happens to a tsunami as it approaches land?” section that it begins to slow and grow in height. Just like other water waves, tsunamis begin to lose energy as they rush onshore – part of the wave energy is reflected offshore, while the shoreward-propagating wave energy is dissipated through bottom friction and turbulence. Despite these losses, tsunamis still reach the coast with tremendous amounts of energy. Tsunamis have great erosional potential, stripping beaches of sand that may have taken years to accumulate and undermining trees and other coastal vegetation. Capable of inundating, or flooding, hundreds of meters inland past the typical high-water level, the fast-moving water associated with the inundating tsunami can crush homes and other coastal structures. Tsunamis may reach a maximum vertical height onshore above sea level, often called a runup height, of 10, 20, and even 30 meters.
Tsunami Warning Centers
Pacific Tsunami Warning Center -Areas of responsibility - warnings for Pacific basin teletsunamis to almost every country around the Pacific rim and to most of the Pacific island states. Interim warning center for Indian Ocean, Caribbean Sea & South China Sea
West Coast/Alaska Tsunami Warning Center - Areas of Responsibility - U.S. West, Alaskan, Atlantic, Puerto Rico, Virgin Islands, and Gulf of Mexico coasts as well as the east and west coasts of Canada