Waves from the December 2004 tsunami traveled as far as Nova Scotia and Peru. Now scientists say that the waves followed mid-ocean ridges like train tracks to get there. Using satellite imagery and computer simulations, scientists have shown that the Southwest Indian Ocean Ridge and the Mid-Atlantic Ridge — long mountain ranges on the seafloor —steered waves through the Atlantic Ocean. The Southeast Indian Ridge, Pacific-Antarctic Ridge, and the East Pacific Rise served as wave guides for waves entering the Pacific Ocean.
The scientists, led by Vasily Titov of the National Oceanic and Atmospheric Administration (NOAA), also used tide gauges throughout the oceans to measure the height of the traveling waves. These readings yielded some surprising results in a detailed map. Gauges near Callao, Peru and others near Nova Scotia actually measured larger waves than gauges near the Cocos Islands, which were much closer to the earthquake’s epicenter. However, many of the gauges in the Indian Ocean either malfunctioned or were destroyed, so some of the largest waves may have been missed.
Mid-ocean ridges did not, however, affect the course of the waves that did most of the damage in the Indian Ocean basin. Long and narrow initial seafloor deformations from the earthquake focused and directed wave energy. While there were no reports of direct tsunami damage outside the Indian Ocean basin, this study showed how energy from localized earthquakes can travel throughout the world’s oceans.