On 29 July 2025, a powerful magnitude 8.8 earthquake struck the Kuril-Kamchatka subduction zone, generating a Pacific-wide tsunami and providing a rare scientific opportunity. Remarkably, NASA and the French space agency’s SWOT satellite passed over the area at the time, capturing the first high-resolution spaceborne images of a major subduction-zone tsunami. Unlike traditional measurements, which rely on sparsely positioned DART buoys, SWOT recorded a wide swath of the ocean surface, revealing complex, braided wave patterns spreading across hundreds of miles. These unprecedented observations challenge conventional assumptions that large tsunamis travel as non-dispersive waves and offer new insights into how energy is distributed mid-ocean, paving the way for improved tsunami forecasting and hazard assessment.
NASA SWOT satellite reveals complex mid-ocean tsunami patterns
Contrary to the traditional depiction of a single, uniform wave crest, the satellite imagery revealed a complex, braided pattern of energy dispersing across hundreds of miles. Conventional instruments rarely capture these details, making this observation a breakthrough in tsunami research. The implications extend beyond imagery. The data suggest that current tsunami forecasting models, which often assume the largest waves travel as largely non-dispersive packets, may need substantial revision. Until now, deep-ocean DART buoys were the primary tools for detecting tsunamis. These highly sensitive instruments provide precise measurements but are limited to specific points in the vast ocean.SWOT can map a 75-mile-wide swath of sea surface height in a single pass, enabling scientists to track the evolving geometry of a tsunami in both space and time. Angel Ruiz-Angulo, lead author from the University of Iceland, described SWOT as “a new pair of glasses.” Before its launch, DART buoys offered only isolated glimpses of the tsunami. With SWOT, researchers can observe a swath up to 120 kilometres wide, delivering unprecedented high-resolution data of the sea surface.
Unexpected tsunami and dispersive wave behaviour revealed
Launched in December 2022 by NASA and CNES, SWOT was originally designed to survey surface water around the globe. Researchers Ruiz-Angulo and Charly de Marez had been analysing data to study ocean eddies when the Kamchatka earthquake struck.The team had not anticipated capturing a tsunami. “We were focused on understanding small oceanic processes and never imagined we would observe a tsunami of this scale,” they noted. Conventional understanding suggests that large tsunamis behave as shallow-water waves. Their wavelength is much greater than the ocean depth, so they propagate without breaking into separate components. SWOT imagery from the Kamchatka event challenges this assumption. Including dispersive effects in numerical models produced simulations that closely matched satellite observations, whereas non-dispersive models did not.Dispersion alters how wave energy spreads as the tsunami approaches the coast. This insight could explain previously unaccounted variations in wave intensity and timing. Ruiz-Angulo noted that trailing waves may modulate the main wave as it nears the shore, and quantifying this energy is crucial for accurate forecasting.
SWOT and DART data enhance Tsunami forecasting and earthquake analysis
SWOT provided a mid-ocean perspective, while DART buoys confirmed wave timing and height at critical locations. Some buoy records did not match initial tsunami predictions, prompting a revision of the earthquake rupture. Researchers extended the rupture southward to 400 kilometres, compared to the initial 300 kilometres estimate.Co-author Diego Melgar explained that tsunami data have proven invaluable for constraining shallow fault slip, particularly since the 2011 Tohoku earthquake. Combining satellite, seismic, and geodetic data remains a challenge but delivers a more complete and accurate picture of seismic events. The Kuril-Kamchatka margin has a history of generating ocean-wide tsunamis, including a magnitude 9.0 earthquake in 1952 that helped establish the Pacific tsunami warning system. During the 2025 event, basin-wide alerts were issued, and SWOT imagery added a new layer of observational evidence to improve future warning systems.Integrating similar satellite observations into real-time monitoring could significantly enhance forecasting, particularly if dispersive effects influence near-coast impacts more than previously understood. Ruiz-Angulo expressed optimism that future satellite data could become a routine part of tsunami prediction.Also Read | Geminids meteor shower 2025: When and where to watch the spectacular December nights with up to 120 shooting stars per hour
