We can capture a swath up to 120 kilometers wide, with unprecedented high-resolution data
On July 29, 2025, a magnitude 8.8 earthquake beneath the Kuril-Kamchatka subduction zone sent a tsunami racing across the Pacific — and for the first time in history, a NASA satellite named SWOT watched it unfold in full, high-resolution detail. What the data revealed was not the orderly, predictable wave science had long assumed, but something far more intricate: a dispersing, scattering system that challenges the foundational models used to protect coastal lives. In the long arc of humanity's effort to read the ocean's warnings, this moment marks a quiet but consequential turning point.
- A once-in-a-generation earthquake — the sixth largest recorded in over a century — sent a Pacific-wide tsunami racing toward coastlines with little margin for error in forecasting.
- SWOT's imagery shattered a long-held assumption: rather than traveling as a single coherent wave, the tsunami fractured into a leading wave trailed by a cascade of smaller ones, exposing a dangerous blind spot in existing models.
- The satellite data also contradicted seismic estimates of the earthquake's rupture length, revealing it stretched 400 kilometers — a third longer than previously believed — forcing scientists to reconcile two fundamentally different mathematical worlds.
- Researchers are now working to bridge the gap between ocean-wave physics and seismic modeling, arguing that combining multiple data types is no longer optional but essential.
- The findings point toward a future where satellites like SWOT feed directly into real-time warning systems, potentially giving coastal communities faster and more precise alerts before the next great wave arrives.
On July 29, 2025, a magnitude 8.8 earthquake tore through the Kuril-Kamchatka subduction zone — one of the most seismically violent stretches of seafloor on Earth — and sent a tsunami spreading across the Pacific. It was the sixth largest earthquake recorded anywhere in more than a century. And this time, a satellite was watching.
NASA's SWOT satellite, launched in late 2022 as a joint mission with France's space agency, was designed to map Earth's surface water in extraordinary detail. Researchers Angel Ruiz-Angulo and Charly de Marez had spent years using it to study small ocean eddies — until this rare and unexpected opportunity arrived. What they captured overturned decades of scientific assumption.
Scientists had long treated large tsunamis as "non-dispersive" — waves that hold their shape across ocean distances because their wavelengths far exceed the ocean's depth. The SWOT data told a different story. The tsunami broke apart as it traveled, its energy scattering into a leading wave followed by a series of trailing ones — the signature of a dispersive system. "We are missing something in the models we used to run," Ruiz-Angulo acknowledged. That missing variability could alter how a wave behaves as it closes in on a coast.
The satellite also exposed a flaw in the earthquake's own portrait. Predictions of when the tsunami would reach two DART buoys — the ocean-floor sensors that form the backbone of existing warning networks — didn't match what actually happened. Working backward from the tsunami's observed behavior, the team determined the earthquake's rupture extended roughly 400 kilometers, significantly longer than the 300 kilometers seismic data alone had suggested.
Co-author Diego Melgar noted that blending tsunami observations with seismic data has grown increasingly important since the catastrophic 2011 Tohoku earthquake in Japan — yet the two disciplines speak different mathematical languages, which is why the integration remains rare. The Kamchatka event made the case again: the more data types scientists combine, the clearer the picture becomes.
The Kuril-Kamchatka zone has long been a crucible of Pacific tsunami history. A 1952 earthquake there helped spark the creation of the international tsunami warning system still in use today. Researchers now hope that SWOT-style satellite observations could one day feed directly into real-time forecasting — offering coastal communities not just earlier warnings, but truer ones.
On July 29, 2025, a magnitude 8.8 earthquake ruptured beneath the Kuril-Kamchatka subduction zone in the Pacific, the sixth largest quake recorded anywhere on Earth in more than a century. It triggered a tsunami that spread across the ocean—and for the first time, a NASA satellite watched the whole thing unfold in high resolution.
The satellite, called SWOT (Surface Water Ocean Topography), had been launched in December 2022 as a joint mission between NASA and France's space agency. Its job was to map Earth's surface water—rivers, lakes, ocean features—with unprecedented detail. Angel Ruiz-Angulo, a researcher at the University of Iceland, and his colleague Charly de Marez had spent more than two years analyzing SWOT data, studying small ocean eddies and currents, when this rare opportunity arrived. They had never imagined they would capture a tsunami.
What they saw challenged decades of assumptions about how tsunamis behave. Scientists have long treated large tsunamis as "non-dispersive"—meaning they maintain a relatively consistent shape as they travel across the ocean, because their wavelengths are much longer than the ocean's depth. But the SWOT data told a different story. The tsunami did not move as a simple, coherent wave. Instead, it spread, scattered, and interacted across vast stretches of the Pacific in patterns far more complex than models predicted. Different parts of the wave moved at slightly different speeds, causing the original wave to break apart into a leading wave followed by a series of trailing waves—the hallmark of a dispersive system.
"I think of SWOT data as a new pair of glasses," Ruiz-Angulo explained in the research published in The Seismic Record. Before SWOT, scientists could only observe tsunamis at specific points in the ocean using DART buoys—instruments designed to detect subtle changes in sea level. Other satellites could capture only a thin line across a tsunami at best. SWOT, by contrast, could image a swath up to 120 kilometers wide with unprecedented resolution. The team combined SWOT observations with measurements from DART buoys positioned throughout the Pacific, creating a picture of the tsunami's behavior that traditional models had missed. "The main impact that this observation has for tsunami modelers is that we are missing something in the models we used to run," Ruiz-Angulo said. That missing variability could mean the main wave gets modulated by trailing waves as it approaches a coast—a factor that had never been properly quantified before.
The satellite data also revealed something unexpected about the earthquake itself. Earlier models based on seismic measurements and land deformation had predicted when the tsunami would arrive at two DART gauges, but the predictions did not match reality. One station detected the tsunami earlier than expected; another recorded it later. Using a technique called inversion—working backward from observed tsunami behavior to estimate earthquake characteristics—the team discovered that the rupture extended farther south than previous studies indicated. The rupture stretched roughly 400 kilometers, significantly longer than the 300 kilometers estimated before. Diego Melgar, a study co-author, noted that tsunami observations have become increasingly valuable for understanding how large earthquakes rupture near the seafloor, a lesson learned after the devastating 2011 magnitude 9.0 Tohoku-oki earthquake in Japan.
The challenge, Melgar explained, is that the physics used to model ocean waves differs fundamentally from the physics used to model seismic waves traveling through Earth's crust. Combining both types of data requires different mathematical frameworks, which is why many earthquake analyses still rely on seismic data alone. Yet the Kamchatka event demonstrated again why mixing as many types of data as possible matters. "It is really important we mix as many types of data as possible," Melgar said.
The Kuril-Kamchatka subduction zone has produced some of the largest tsunamis ever recorded in the Pacific. A magnitude 9.0 earthquake in the same region in 1952 triggered a massive tsunami that ultimately helped drive the creation of the international tsunami warning system. That network played a key role in issuing Pacific-wide alerts during the 2025 tsunami. As satellite technology continues to improve, researchers hope observations like those collected by SWOT could one day become part of near real-time tsunami forecasting systems, providing faster and more accurate warnings for coastal communities in harm's way.
Notable Quotes
Before, with DARTs we could only see the tsunami at specific points in the vastness of the ocean. Now, with SWOT, we can capture a swath up to about 120 kilometers wide, with unprecedented high-resolution data of the sea surface.— Angel Ruiz-Angulo, University of Iceland
The main impact that this observation has for tsunami modelers is that we are missing something in the models we used to run.— Angel Ruiz-Angulo
The Hearth Conversation Another angle on the story
So SWOT was built to study rivers and lakes, not tsunamis. How did it end up capturing this one?
Timing and luck. The satellite happened to be passing over the Pacific when the tsunami was spreading. Ruiz-Angulo and de Marez had been analyzing SWOT data for years, studying ocean eddies and currents. They were in the right place, with the right instrument, when something rare happened.
What made this tsunami observation so different from what scientists already knew?
Before SWOT, we could only see tsunamis at specific points—where DART buoys happened to be stationed. It was like watching a concert through a single keyhole. SWOT let us see 120 kilometers of the wave at once, in high resolution. And what we saw contradicted what we thought we knew.
Which was what, exactly?
That big tsunamis travel as simple, coherent waves that don't change shape much over long distances. But this one didn't. It broke apart into multiple waves moving at different speeds, spreading and scattering across the ocean. The models we've been using for decades didn't predict that.
Does that mean the old models are wrong?
Not wrong, exactly. But incomplete. There's extra variability in how these waves behave that we weren't accounting for. When a tsunami approaches a coast, those trailing waves could amplify or modify the main wave in ways we haven't properly measured before.
And the earthquake itself—the data revealed something unexpected there too?
Yes. By working backward from the tsunami observations, researchers figured out the earthquake rupture was longer than seismic data alone suggested. About 400 kilometers instead of 300. That's a significant difference for understanding how the fault broke.
Why is combining tsunami data with seismic data so hard?
They operate on different physics. Seismic waves travel through solid rock. Tsunami waves travel through water. The mathematical models for each are completely different. Getting them to work together requires translating between two different languages.