SWOT satellite reveals hidden tsunami signals linked to trench operations near Kamchatka earthquake

image:

About one hour after the earthquake, the SWOT captured the offshore tsunami wave field near Kamchatka shown as a red and blue measuring patch. These data constrained the initial tsunami-inferred sea surface height (yellow-purple pattern) and enabled forward simulations that reproduce the surrounding tsunami wave field (red-blue) in agreement with SWOT observations.

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Credit: Bjarke Nelson

Improving tsunami risk assessments depends on understanding what happens at the moment an earthquake erupts beneath the seafloor, especially near deep-ocean trenches where measurements are often scarce. When a powerful 8.8-magnitude earthquake struck off Russia’s Kamchatka Peninsula on July 29, 2025, it triggered a tsunami that traveled across the Pacific Ocean.

New research published in the journal Science shows that spaceborne satellite altimetry can detect 2D tsunami wave patterns near an earthquake source, providing insight into coastal risk assessment and preparedness planning.

The international study, led by San Diego State University Associate Professor Ignacio Sepulveda of the Department of Civil, Structural and Environmental Engineering in close collaboration between DTU Space at the Technical University of Denmark; Scripps Institution of Oceanography at the University of California San Diego; The Institute of Geography at the Pontifical Catholic University of Valparaiso used data from the US-French Surface Water and Ocean Topography, or SWOT, satellite. The team found that the SWOT analysis detected a distinct train of tsunami waves with a “dispersive” wavelength about 1,000 kilometers from the earthquake.

Researchers link these tsunami waves to a seismic rupture occurring less than 10 kilometers below the trench along the Kamchatka subduction zone, a critical area under the sea floor, where seismic processes are often difficult to measure using conventional ground geodesy, seismic instruments, or deep-water tsunami sensors.

“We are highlighting characteristics of earthquakes that advance our knowledge and may clarify scientific questions for the community,” Sepulveda said. “This helps us improve our understanding of near-trench rupture earthquakes and helps coastal communities better prepare for the earthquake and tsunami risks they face.”

Large earthquakes along subduction zones can suddenly dislodge the seafloor, generating long ocean waves capable of crossing entire ocean basins. However, observing the processes occurring near the trench, where one tectonic plate subducts under another, remains difficult.

Five nearby Deep Ocean Assessment and Tsunami Reporting, or DART, sensors recorded the front of the Kamchatka tsunami. The closest measurement of its height from top to bottom is 1.32 metres. However, the problem of shallow slippage near the trench may be difficult to solve using those records alone because the sensors are spaced far apart and shorter wavelength signals can be diminished at depth.

About 70 minutes after the earthquake, SWOT passed approximately 600 km seaward from the epicenter and imaged the tsunami wave field in two dimensions. Using radar phase coherence, the satellite measures sea surface height with an accuracy of one centimeter. Large-scale observations captured both the leading peak and a series of subsequent short-wavelength disturbances.

In the Kamchatka event, the trailing wave train indicates an additional rupture shallower than 10 km, with a center point along strike between 49.5°N and 52.5°N. The study shows that SWOT provides reliable constraints beyond the scope of conventional oceanographic, geodetic and seismic observations.

The research also places the Kamchatka observations in a broader pattern. SWOT previously observed dispersive tsunami waves near the Loyalty Islands on May 19, 2023, and again after the May 2, 2025, magnitude 7.4 Drake Passage earthquake. Together, these independent findings suggest that dispersive tsunami signals may be more common than previously recognized, and that previous gaps likely reflect limitations in monitoring rather than their rarity in nature.

“Capturing this tsunami while mapping out its strengths, weaknesses, opportunities and threats (SWOT) near its source gave us important data on the rupture of the earthquake, how it led to the resulting tsunami and the physics that occurs near the trench,” said Alice Gabriel, an associate professor at Scripps Institution of Oceanography. “This should help us build more physically realistic models of tsunami generation and improve risk assessments on vulnerable coastlines around the world.”

The study highlights three key implications for risk science: dispersive modeling is remarkably useful in characterizing tsunami waves near their source; Satellite altimetry can add unique limitations when it detects tsunami waves close to where they originate; Large-scale elevation measurement provides a transformative tool for understanding earthquake rupture and improving tsunami risk assessments.

“These dispersed wave trains are not just curiosities. They carry information about where the closed fault – which causes the accumulation of energy over decades to centuries of plate movement – slipped during the earthquake. In particular, they provide unique evidence of slip near the trench, which is very difficult to constrain,” said Matías Carvajal, a professor at the Institute of Geography.

“This discovery shows the importance of the United States and the world investing in the ability of satellites to measure what is happening on our planet in terms of geohazards,” Sepulveda said. “This satellite helps us understand tsunami and earthquake risks through a new, clearer lens than before.”

By improving how scientists resolve the behavior of near-trench earthquakes and the tsunami signals they produce, the research supports stronger earthquake rupture models and risk assessment methods used to assess coastal hazards.

“We have contributed by processing data from SWOT and other satellites for analysis. This enables other researchers to improve models of how tsunamis spread and develop. In the long term, this could lead to strengthening tsunami warning systems in vulnerable coastal areas,” said Bjarke Nilsson, a PhD student at DTU Space.

The research reflects a joint international effort to advance scientific understanding of risks from earthquakes and improve the basis for assessing tsunami risks around the world.

Article title

SWOT detects dispersal tsunami associated with a source near the trench in the 2025 Kamchatka earthquake.

Date the article was published

26-March-2026

COI statement

The authors declare that they have no competing interests.

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