Yesterday marked the one year anniversary of the largest earthquake in Japan's recorded history — the quake responsible for triggering the massive and deadly Tohoku-oki tsunami. The animation up top, released yesterday by NASA, shows the tsunami's motion across the Pacific basin in the 22 hours following the earthquake.

Scientists have known for some time now that the shape of the seafloor can play a huge role in determining how the waves of a tsunami spread and change as they travel. Now, satellite data collected over the course of the devastating natural disaster has provided scientists the clearest idea yet of how these underwater features can direct a tsunami's power over vast distances. According to NASA:

Scientists had suspected that underwater mountains and chasms, as well as islands, played a role in deflecting tsunami waves in some places and amplifying them up in others. But it was not until three satellites passed over such waves in March 2011 that they could confirm it.

Researchers from NASA' Jet Propulsion Laboratory (JPL) and the Ohio State University (OSU) used satellite altimeters to observe "merging tsunamis" — wave fronts that combine to form single waves at double the previous height. Such waves can travel hundreds to thousands of kilometers without losing power.

The team examined measurements of the wave fronts as gathered by the Jason-1, Jason-2, and Envisat satellites, each of which flew over the tsunami at a different location. Altimeters on each satellite measure sea level changes to an accuracy of a few centimeters. They found that the March 2011 tsunami doubled in intensity when passing over rugged ocean ridges and around islands in the middle of the Pacific Ocean.

Tony Song, who led the study that created the animation up top, said "it was a one in ten million chance" that he and his team were able to observe this double wave with satellites.

Read more over at NASA.