The satellite known as Surface Water Ocean Topography (SWOT) was in the right place at the right time when an earthquake with a magnitude of 8.8 struck off the Kamchatka Peninsula on July 29. This event became the sixth strongest earthquake recorded since 1900.
An article published in The Seismic Record reports that the satellite captured a high-quality image of a large tsunami in a subduction zone for the first time. Instead of the expected simple wave smoothly spreading across the ocean, the data revealed a complex picture: the waves interacted, scattered, and spread across the Pacific Ocean in a significantly more chaotic manner than previously thought.
Ángel Ruiz-Angulo from the University of Iceland and his team combined satellite data with readings from deep-water DART buoys located along the tsunami's path, which helped refine estimates of the earthquake that triggered these waves.
Ruiz-Angulo compared the SWOT data to new glasses. Previously, scientists could only see tsunamis at specific points using DART buoys, while other satellites captured only a narrow line across the tsunami. SWOT, however, offers a swath up to 120 kilometers wide with unprecedented resolution of sea surface data.
Launched in December 2022 as part of a joint mission between NASA and the French space agency, SWOT's main task is to conduct the first global survey of the planet's surface waters, including oceans, rivers, and lakes. Ruiz-Angulo and his colleague Charlie de Marrez analyzed the satellite data for over two years, studying everyday ocean processes, and did not expect to capture a tsunami.
The research results challenge the traditional understanding of large tsunami behavior. Scientists have typically described them as non-dispersive waves, assuming they would propagate as a single entity rather than breaking into multiple waves. SWOT data calls this theory into question.
When researchers compared satellite data with computer models, it turned out that models accounting for wave dispersion more accurately reflect the real situation than traditional ones. This means that the main wave can change depending on the trailing waves as it approaches the shore, and this effect requires quantitative assessment.
The team also found a discrepancy between the predicted and actual arrival times of the tsunami recorded by two DART buoys. One sensor recorded the tsunami earlier than expected, while the other recorded it later.
Analyzing the buoy data allowed the team to reassess the tsunami's source. It turned out that the rupture from the earthquake extended further south than previously thought, covering approximately 400 kilometers, which is significantly more than the 300 kilometers indicated in other models.
Diego Melgar, a co-author of the study, noted that after the catastrophic 9.0 magnitude earthquake in Japan in 2011, it became clear that tsunami data contains valuable information for determining the boundaries of slip at shallow depths. His laboratory and other research groups are working to incorporate DART data into earthquake and tsunami analysis, but this has not yet become standard practice.
Melgar emphasized that combining different types of data is critically important. Hydrodynamic models needed for DART modeling differ significantly from seismic wave propagation models used for analyzing solid Earth data, but maximizing the mixing of data types is key to accurate predictions.
The Kuril and Kamchatka subduction zone is a source of some of the most powerful tsunamis in history, including the devastating 1952 event caused by a 9.0 magnitude earthquake, which led to the creation of an international tsunami warning system. This system also issued warnings during the 2025 events.
Ruiz-Angulo expressed hope that the results of such studies in the future will serve as a foundation for the need for satellite observations that can predict tsunamis in real or near-real time.
