A NASA satellite caught a giant tsunami doing something scientists didn’t expect
When a huge earthquake struck near Kamchatka, the SWOT satellite captured an unprecedented, high-resolution view of the resulting tsunami as it crossed the Pacific. The data revealed the waves were far more complex and scattered than scientists expected, overturning the idea that large tsunamis travel as a single, stable wave. Ocean sensors confirmed the quake’s rupture was longer than earlier models suggested. Together, the findings could reshape how tsunamis are modeled and predicted.
A satellite designed to measure the height of the ocean surface was in the right place at the right time when a powerful earthquake off Russia's Kamchatka Peninsula sent a tsunami across the Pacific in late July.
The spacecraft, known as the Surface Water Ocean Topography or SWOT satellite, recorded the first high resolution space-based track of a major subduction zone tsunami, according to researchers writing in The Seismic Record.
Instead of a simple wave moving cleanly across the ocean, the satellite data revealed a surprisingly intricate pattern of waves spreading, interacting, and scattering across the basin. Scientists say this detailed view could improve understanding of how tsunamis travel and how they may ultimately affect coastlines.
Combining satellite data with ocean sensors
To better understand the event, Angel Ruiz-Angulo of the University of Iceland and his colleagues combined the satellite observations with measurements from DART (Deep-ocean Assessment and Reporting of Tsunamis) buoys located along the tsunami's path. These deep-ocean sensors helped them refine estimates of the earthquake that triggered the waves.
The July 29 earthquake struck in the Kuril-Kamchatka subduction zone with a magnitude of 8.8, making it the sixth largest earthquake recorded worldwide since 1900.
"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."
A satellite built for water, not disasters
SWOT was launched in December 2022 as a joint mission between NASA and the French space agency Centre National d'Etudes Spatiales. Its main goal is to deliver the first global survey of Earth's surface water, including oceans, rivers, and lakes.
Ruiz-Angulo said he and co-author Charly de Marez had spent more than two years studying SWOT data to understand everyday ocean features such as small eddies. "[We] 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."
Rethinking how giant tsunamis behave
Because the wavelength of large tsunamis is much longer than the depth of the ocean, scientists have traditionally described them as "non-dispersive." In simple terms, this means the wave is expected to travel as a single, stable form rather than breaking into multiple waves that spread out over time.
"The SWOT data for this event has challenged the idea of big tsunamis being non-dispersive," Ruiz-Angulo explains.