In open ocean, even for a large tsunami, the amplitude or height of the wave rarely exceeds a couple of meters (6 feet). However, as the tsunami approaches the shore, the shallow water causes the wave to slow down and its height gets amplified. This tsunami reached a height of 30 m (90 feet).
Red represents water that is above sea level, blue below. Time after the earthquake is given in hours in the lower right-hand corner.
Credit: Anthony Sladen, Tectonics Observatory; Commissariat à l'Energie Atomique (CEA)
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For more information:
Coseismic Slip and Afterslip of the Great Mw 9.15 Sumatra–Andaman
Earthquake of 2004
Sumatran Plate Boundary Project