NASA Satellite Captures First-Ever High-Res View of a Giant Pacific Tsunami

A rare satellite view captured a major Pacific tsunami in unprecedented detail, revealing wave behaviors scientists did not expect.

A satellite designed to track the height of the ocean’s surface proved its capabilities when a powerful earthquake struck off the Kamchatka Peninsula in late July, sending a tsunami across the Pacific.

According to researchers writing in The Seismic Record, the Surface Water Ocean Topography (SWOT) satellite produced the first detailed space-based view of a major tsunami generated by a subduction zone event.

Its observations revealed a surprisingly intricate pattern of waves spreading and interacting across the basin. These patterns could offer scientists new insight into how tsunamis travel and how they may pose risks to coastal regions.

To better understand the magnitude 8.8 earthquake that occurred on 29 July, Angel Ruiz-Angulo of the University of Iceland and his team combined the satellite’s measurements with data from DART (Deep-ocean Assessment and Reporting of Tsunamis) buoys that were directly in the tsunami’s path. This quake, located in the Kuril-Kamchatka subduction zone, ranks as the sixth largest recorded worldwide since 1900.

SWOT’s New View of the Ocean

“I think of SWOT data as a new pair of glasses,” said Ruiz-Angulo. “Before, with DARTs we could only see the tsunami at specific points in the vastness of the ocean. There have been other satellites before, but they only see a thin line across a tsunami in the best-case scenario. Now, with SWOT, we can capture a swath up to about 120 kilometers wide, with unprecedented high-resolution data of the sea surface.”

Launched in December 2022 through a partnership between NASA and the French space agency Centre National d’Etudes Spatiales, SWOT was created to deliver the first global assessment of Earth’s surface water.

This animation shows the simulated tsunami wave heights generated by the M8.8 earthquake. Around 70 minutes after the earthquake, the path of the SWOT satellite appears, shown in slow motion to illustrate how the fast-moving satellite captured the tsunami and the dispersive waves that followed the main crest. Credit: Angel Ruiz-Angulo

Ruiz-Angulo said he and study co-author Charly de Marez “had been analyzing SWOT data for over two years understanding different processes in the ocean like small eddies, never imagining that we would be fortunate enough to capture a tsunami.”

Since the wavelength of a big tsunami is longer than the ocean’s depth, researchers often consider these tsunamis to be “non-dispersive.” That is, they mostly remain intact as a singular wave shape as they travel, instead of breaking up or “dispersing” into a leading wave and a train of trailing waves.

“The SWOT data for this event has challenged the idea of big tsunamis being non-dispersive,” Ruiz-Angulo explains.

Numerical models of tsunami propagation with dispersion were a better match for the satellite observations of the Kamchatka tsunami, he and his colleagues concluded.

Implications for Tsunami Forecasting

“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 added. “This ‘extra’ variability could represent that the main wave could be modulated by the trailing waves as it approaches some coast. We would need to quantify this excess of dispersive energy and evaluate if it has an impact that was not considered before.”

The researchers also realized the tsunami predicted by an earlier model based on seismic and land deformation data did not exactly match the tsunami observations collected by two of the DART tide gauges. The tsunami based on the earlier model was predicted to hit one gauge earlier and one gauge later than observed. The researchers used the DART data in an analysis called inversion to reevaluate the tsunami source.

Redefining the Earthquake Rupture

They concluded that the Kamchatka earthquake source extended further to the south and that the earthquake rupture length was 400 kilometers—significantly longer than the 300 kilometers predicted by other models.

“Ever since the 2011 magnitude 9.0 Tohoku-oki earthquake in Japan, we realized that the tsunami data had really valuable information for constraining shallow slip,” said study co-author Diego Melgar.

Since then, Melgar’s lab and others have been working on ways to include DART data in inversions, “but it is still not always done because the hydrodynamic models needed to model DARTs are very different than the seismic wave propagation ones for modeling the solid Earth data. But, as shown here again, it is really important we mix as many types of data as possible,” Melgar said.

One of the largest recorded Pacific tsunamis was triggered by a massive magnitude 9.0 earthquake in 1952 in the same Kuril–Kamchatka subduction zone. That tsunami led to the creation of the international alert system that led to Pacific-wide warnings during the 2025 event.

“With some luck, maybe one day results like ours can be used to justify why these satellite observations are needed for real or near-real time forecasting,” Ruiz-Angulo said.

Reference: “SWOT Satellite Altimetry Observations and Source Model for the Tsunami from the 2025 M 8.8 Kamchatka Earthquake” by Angel Ruiz‐Angulo, Diego Melgar, Charly de Marez, Aurélien Deniau, Francesco Nencioli and Vala Hjörleifsdóttir, 26 November 2025, The Seismic Record.
DOI: 10.1785/0320250037

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