When the 8.8 magnitude earthquake shook the subduction zone between Kuril and Kamchatka in the Russian Far East on July 29, 2025, scientists expected the arrival of the “usual” tsunami: a powerful, compact wave, ready to cross the Pacific as a single block. This is what has been taught for decades: the larger the tsunami, the more it behaves like a single mass that proceeds without “discomposing”.
And instead, this time, history took an unexpected detour. The SWOT satellite, the mission born from the collaboration between NASA and the French space agency, was located right above the area of the ocean affected by the passage of the wave. A rare stroke of scientific luck. The image that SWOT recorded was not just a beautiful marine-themed photo: it was a slap in the face to certainties. The ocean appeared to be crossed by a very intricate mosaic of filaments, lines, ripples that split and mixed together like hair in the wind. Nothing but a uniform wave.
The study, published in the journal The Seismic Recordexplains that for the first time we saw a large tsunami in action. And what we have seen forces us to rewrite some pages of the manuals.
Why the SWOT picture changes the predictions
Until yesterday, it was almost taken for granted that “monumental” tsunamis were non-dispersive waves, that is, stable, incapable of breaking down into different components. A kind of train that takes all the carriages with it, without ever changing places.
But the SWOT data shows something else entirely. The 2025 tsunami front was an embroidery of energies that separated, widened and intertwined with each other. And when the researchers inserted the effects of dispersion, that is, the tendency of a wave to break down part of its energy into smaller waves, into the mathematical models, the simulations finally returned to resembling what SWOT had photographed.
And this is not a detail. It means that as a wave approaches the coast, its energy may be distributed in a more complex way than expected, altering the timing and manner of impact. We are talking about crucial information for those involved in tsunami warnings, civil protection and coastal infrastructure.
A puzzle that comes together
DART buoys, anchored in the Pacific, provided the chronology of the wave’s passage. Yet something didn’t add up: two stations recorded the arrival of the tsunami earlier or later than forecast. An anomaly? No, a clue.
By incorporating signals from the buoys into the models, the team reconstructed the seismic fracture with greater precision: it was not 300 kilometers long, as previously thought, but almost 400, and it extended further south. This shift greatly changes the identikit of the earthquake and, consequently, the development of the wave.
For years it has been said that tsunamis contain valuable information on seismic rupture. But integrating them into models is not easy: it requires an ongoing dialogue between ocean physics and seismology. SWOT, with its “broad view,” makes that dialogue much richer.
Because this discovery can improve tsunami warnings
The Kuril-Kamchatka area has a long history of earthquakes capable of setting gigantic waves in motion. It is no coincidence that it was there, in 1952, that the Pacific warning system was born.
Now SWOT enters the game as a new player: it does not replace buoys or seismic data, but adds a tool that allows you to see the tsunami as it travels. If we can one day integrate these observations in near real time, predictions could become much more accurate. Tsunamis will not become less complex, but at least we will no longer be blind to their transformations.
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