New insight into the early stages of tsunami formation could help improve future tsunami warning systems.

When a magnitude 8.8 earthquake struck off Russia’s Kamchatka Peninsula on July 29, 2025, it generated a tsunami that traveled across the Pacific Ocean. New research published in Science shows that satellite measurements can detect tsunami wave patterns near the earthquake’s source, providing new insights into tsunami formation and potentially improving future tsunami hazard assessments.

Using data from the French–American Surface Water and Ocean Topography (SWOT) satellite, the researchers identified a distinct train of short-wavelength, so-called dispersive tsunami waves within about 1,000 kilometers of the earthquake. These faint signals are typically difficult to detect with conventional ocean-based instruments.

“Improving tsunami hazard assessments requires a better understanding of what happens when an earthquake ruptures beneath the seafloor, especially near deep-ocean trenches, where measurements are scarce. Data from the SWOT satellite help fill this gap,” says Assistant Professor Ignacio Sepúlveda from San Diego State University, who led the study published in Science.

“We’re illuminating properties of earthquakes that advance our knowledge and clarify scientific questions for the community. This helps us improve our understanding of earthquakes that rupture close to the trench and helps coastal communities better prepare for the seismic and tsunami hazards they face.”

The study is based on an international collaboration between San Diego State University, DTU Space at the Technical University of Denmark, Scripps Institution of Oceanography at the University of California, San Diego, and the Instituto de Geografía at the Pontificia Universidad Católica de Valparaíso in Chile.

“We contributed by processing data from SWOT and other satellites for the analysis. This enables other researchers to improve models of how tsunamis propagate and develop. In the long term, this could strengthen tsunami warning systems in vulnerable coastal regions,” says Bjarke Nilsson, PhD student at DTU Space and second author of the study.

The analysis indicates that the waves originate from rupture processes less than 10 kilometers beneath the seafloor near the ocean trench in the Kamchatka subduction zone, an area where measurements are sparse and scientific understanding remains limited.

About 70 minutes after the earthquake, SWOT passed roughly 600 kilometers from the epicenter and captured the tsunami wavefield in two dimensions. With centimeter-level precision, the satellite’s wide-swath altimetry recorded both the leading wave and a sequence of trailing disturbances.

These trailing waves indicate additional rupture at shallow depths near the ocean trench - information that is difficult to obtain from traditional seismic networks and deep-ocean sensors alone.

“Capturing this tsunami with SWOT near its source gave us crucial data on the earthquake rupture, how it generated the resulting tsunami and the physics playing out near the trench,” says Alice Gabriel, Associate Professor at Scripps Institution of Oceanography.

“That should help us build more physically realistic models of tsunami generation and improve hazard assessments for vulnerable coastlines around the world”.

Previous SWOT observations from earthquakes in 2023 and 2025 suggest that the dispersive wave signals may be more common than previously recognized.

“These dispersive wave trains carry information about where the locked fault – which causes energy to build up over decades to centuries of plate motion – slipped during the earthquake. In particular, they provide unique evidence for slips very close to the trench, which is otherwise extremely difficult to constrain,” says researcher Matías Carvajal at Instituto de Geografía.

“This study highlights the power of an interdisciplinary approach. Observations of the ocean from space reveal processes within the Earth that we cannot directly observe, ultimately improving hazard assessment”.

The study highlights three key implications for hazard science:
* modeling dispersive tsunami waves, where different wave components travel at different speeds, can improve how waves are characterized near their source.
* satellite altimetry provides unique data that improve and refine tsunami models when observations are made close to where tsunamis originate.
* wide-swath altimetry offers a powerful new tool for understanding earthquake rupture and improving tsunami hazard assessments and complements existing observation systems.

By improving how scientists resolve earthquake processes near deep-ocean trenches, the study contributes to more accurate tsunami models and strengthens the basis for assessing coastal hazard risks worldwide.