Observations made by a satellite operated by U.S. and French space agencies shortly after a powerful earthquake struck Russia's Kamchatka Peninsula last year are helping scientists better understand how tsunamis form and spread.

Researchers say the findings could improve predictions of future tsunamis and earthquakes in subduction zones—areas near ocean trenches where two tectonic plates meet and one slides beneath the other. These zones often produce the strongest tsunamis.

The magnitude 8.8 earthquake hit on July 29, 2025, triggering a tsunami that propagated across the Pacific Ocean. Tsunamis—series of extremely long, powerful ocean waves—are usually caused by large seafloor movements during underwater earthquakes or landslides.

The NASA-CNES Surface Water and Ocean Topography (SWOT) satellite captured data within 70 minutes of the earthquake. It observed not only the leading wave of the tsunami but also a distinct pattern of smaller waves trailing behind it. While such wave patterns had been predicted in computer models and theoretical studies, confirming them with real-world observations had been challenging, researchers said.

"I believe SWOT represents a new lens for observing and studying tsunamis and their generation," said Ignacio Sepúlveda, professor of coastal engineering at San Diego State University and lead author of the study published this week in Science. "It is also likely to improve our understanding of the physical mechanisms that generate tsunamis, including earthquakes."

Traditional deep-ocean pressure sensors and other satellites have limitations in coverage and measurement, making it difficult to capture the full structure of tsunami waves, especially near the trench. SWOT, however, scans wide swaths of the ocean, producing two-dimensional maps of sea surface height. This allows scientists to see the shape, direction, and spacing of tsunami waves in far greater detail.

Tsunamis are among the most destructive natural forces, with powerful waves radiating outward from the point of origin. They can cause severe and deadly coastal flooding. The 2025 tsunami did not result in significant loss of life, but other events, such as the 2004 Indian Ocean tsunami, claimed about 230,000 lives.

The study found that the July 2025 tsunami originated within roughly 10 kilometers (6 miles) of the trench, the location in the seafloor where two tectonic plates meet. Such precise determination was not possible with traditional land-based instruments or sparse seafloor sensors alone.

The researchers also discovered that when earthquake movements extend close to the trench, they can produce shorter waves that travel more slowly and spread out over time, forming a trailing pattern behind the main tsunami front. This behavior causes different parts of the wave to move at different speeds, with longer waves leading and shorter waves lagging behind.

Furthermore, the study showed that the strength of trailing waves increases when the earthquake movement is closer to the trench, indicating a direct link between the waves and the earthquake’s location and dynamics.

"This opens a new window to understand in a better way what happens with earthquakes and tsunamis near the trench," Sepúlveda said. "In the future, this knowledge will allow us to improve models for evaluating tsunami hazards in coastal communities and make them more resilient."

Huge quake rocks Russia's Far East, triggering tsunami warnings across the Pacific. Read full story.

-Reporting by Marta Serafinko in Gdansk, Poland; Editing by Will Dunham/Reuters