Satellites may in the future become an important tool in efforts to improve the models used to assess and forecast tsunamis worldwide. This is demonstrated in a new study published in the scientific journal Science, co-authored by a PhD student from DTU Space.
The study describes how measurements from climate satellites provide new insight into the early stages of tsunami formation. The observations primarily come from the French-American SWOT satellite, which delivered unique measurements of tsunami waves triggered by a powerful underwater earthquake on 29 July 2025 near Russia's Kamchatka Peninsula in the North Pacific. The earthquake had a magnitude of 8.8.
"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 results indicate that satellite-based measurements can complement existing sensors, leading to more accurate models and improved tsunami forecasting.
In the right place at the right time by chance
As it orbited Earth, the SWOT satellite happened to pass directly over the North Pacific region where the powerful earthquake occurred.
"We were fortunate that the SWOT satellite was over the area at exactly the right time. If it had passed just 15 minutes earlier or later, we would not have obtained these unique data," says Bjarke Nilsson.
Here, the satellite captured wave motion with a level of detail not previously achievable from space.
Satellites such as SWOT cannot be used for direct warnings, as they do not continuously monitor the same locations. However, when a satellite passes at the right place and time, its data can help improve tsunami models and strengthen hazard assessments - particularly in regions of the Pacific that are frequently affected by underwater earthquakes.
Satellite altimetry - precise measurements of sea surface height from space - can therefore become an important complement to existing methods for modelling and forecasting tsunamis.
"Ten years ago, only a few satellites could detect these short-lived tsunami signals in the Pacific. Today, there are about a dozen, which greatly increases the chances of observing them," says Bjarke Nilsson.
The SWOT satellite, launched in 2022, measures sea-surface height with unprecedented precision.
The researchers found the tsunami's 'fingerprint'
The earthquake occurred along the Kuril-Kamchatka trench, one of the world's most active seismic zones. The event generated a tsunami, but it was not only the leading wave that made the satellite observations remarkable.
SWOT detected a series of short-wavelength, so-called dispersive tsunami waves trailing behind the main wave. These waves act as a kind of "fingerprint" of the tsunami and can be used for more precise modelling of its origin and propagation.
In the scientific article, the researchers show that these waves can reveal whether the earthquake rupture extended to areas near the deep-sea trench - a critical but difficult-to-measure region for the generation of the most destructive tsunamis.
Better preparedness for earthquake and tsunami hazards
Normally, an underwater earthquake is first detected through seismic measurements, while the tsunami itself is only recorded when it passes sensors in high-risk areas. These data are used to estimate where and when waves are expected to reach coastlines.
By supplementing these methods with satellite data, predictions can become more accurate. Using altimetry from SWOT and similar satellites helps scientists detect tsunami wave patterns very close to the earthquake source.
"We're illuminating properties of earthquakes that advance our knowledge and clarify scientific questions," says the study's lead author on the article in Science, Assistant Professor Ignacio Sepúlveda of San Diego State University.
"This helps us improve our understanding of earthquakes that rupture close to the sea trench and helps coastal communities better prepare for the seismic and tsunami hazards they face".
The study combines data from 11 satellites, including SWOT and several European satellites launched by ESA. While primarily designed for climate research, their high precision also makes them well-suited to detecting the subtle signals of tsunami waves in the open ocean.
