The ocean doesn’t easily give up its secrets, but a recent analysis of a 2025 tsunami triggered by a powerful earthquake off the coast of Russia’s Kamchatka Peninsula has revealed a hidden clue about how these devastating waves are born. Scientists, using data from the Surface Water and Ocean Topography (SWOT) satellite, detected a secondary, smaller wave signal trailing the initial tsunami – a “choppy tail” – that points to a rupture occurring remarkably close to the ocean trench. This discovery, published in the journal Science, offers a new way to understand earthquake mechanics and could improve tsunami forecasting.
For decades, accurately modeling tsunamis has been a challenge. Traditional methods rely on seismic data and readings from deep-ocean buoys – the Deep-ocean Assessment and Reporting of Tsunamis (DART) sensors – to estimate where and how the seafloor moved during an earthquake. But these methods often struggle to pinpoint the rupture zone with precision, particularly when it occurs near the trench where one tectonic plate slides beneath another. The new research demonstrates that the trailing waves observed by SWOT provide a direct, space-based record of shallow-water rupture, a detail often lost in conventional analyses.
A Satellite’s View of the Rupture
The 8.8 magnitude earthquake struck off Kamchatka in July 2025, generating a tsunami that traveled across the Pacific Ocean. Whereas DART sensors detected the initial wave, it was the SWOT satellite that captured the subtle, yet crucial, detail of the trailing waves approximately 70 minutes after the main event. SWOT, launched in 2022, doesn’t measure sea height at a single point like older altimetry satellites. Instead, it scans a broad strip of the ocean, providing a two-dimensional view of wave direction and curvature. This wider perspective allowed researchers to observe the short-wavelength waves lagging behind the primary tsunami, a phenomenon known as dispersion.
“These trailing wave packets extended about 31 miles and behaved differently from the main front, retaining a clear signature,” explained Ignacio Sepúlveda, lead author of the study and a researcher at San Diego State University (SDSU). “This pattern narrowed the likely source of the earthquake to a relatively short band along the trench off southern Kamchatka.” The team at SDSU combined the satellite data with land movement measurements and offshore wave records to build and test different earthquake models.
Filling the Gaps in Existing Data
The five DART sensors near the earthquake’s epicenter confirmed the presence of a powerful wave, with the closest instrument measuring a crest-to-trough height of approximately 4.3 feet. However, these sensors, while vital, have limitations. DART sensors lose sensitivity to shorter signals in deep water, and the sparse network leaves gaps in coverage. The SWOT satellite data effectively filled these gaps, providing a continuous view of wave direction, curvature, and spacing across the ocean surface.
The analysis revealed that the earthquake’s rupture extended close to the trench, causing a steep uplift of the seafloor. This near-trench motion is known to generate shorter wavelengths, creating the observed “choppy tail” behind the main tsunami wave. Scientists had long theorized this connection, but the Kamchatka event provided the first direct space-based evidence linking the trailing waves to shallow-water rupture.
Improving Tsunami Forecasts
The findings have significant implications for tsunami warning systems. Current models often assume that earthquake rupture occurs deeper beneath the seafloor. If these models underestimate the amount of movement near the trench, they can underestimate the potential for coastal inundation. “We’re illuminating properties of earthquakes that advance our knowledge and may clarify scientific questions for the community,” said Sepúlveda. His team argues that future models should incorporate the possibility of shallow-water rupture, particularly when trailing waves are observed.
This isn’t the first time SWOT has demonstrated its potential for tsunami research. An earlier study, published in 2026, showed that the satellite could map wave patterns in two dimensions following a 2023 tsunami near the Loyalty Islands in the southwest Pacific. The SDSU team has also identified a similar trailing wave pattern following an earthquake near Drake Passage, suggesting that these signals may be more common than previously thought. The challenge lies in capturing these signals, as SWOT revisits most locations only about every 11 days.
While SWOT won’t replace existing tsunami warning systems, it can serve as a valuable tool for cross-checking data from seafloor sensors, coastal gauges, and seismic networks. The satellite’s unique perspective offers a more complete picture of tsunami generation, potentially leading to more accurate and timely warnings.
The National Weather Service is continuing to monitor seismic activity in the region and refine its tsunami forecasting models. The next major update to the agency’s tsunami warning system is scheduled for early 2026, incorporating data from SWOT and other advanced sensors.
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