🌊 A satellite captured the birth of a giant tsunami live

From Earth's orbit, an observer witnessed the birth and course of a colossus of the seas.

Back to July 29, 2025. A major earthquake off the Kamchatka Peninsula shook the ocean floor, generating a tsunami that crossed the Pacific. By a fortunate coincidence, the SWOT satellite, the result of a collaboration between NASA and CNES, was flying over the area at the same time.


Initially designed to map variations in water height on Earth with unparalleled precision, it thus became the first space witness to capture the entirety of such an event with exceptional resolution. This observation, combined with data from coastal buoys, offers an unprecedented picture of the forces at play.

The waves reveal their secrets

The analysis of the data, published in The Seismic Record, produced a major discovery. The tsunami did not behave as a single, simple displaced mass of water. On the contrary, SWOT's sharp eye distinguished a never-before-seen structure, where a main imposing wave was followed by several smaller ones, forming a kind of procession. This direct observation challenges the postulate of the non-dispersive model, which prevailed for large-scale tsunamis.

SWOT's strength lies in the width of its field of view, covering nearly 75 miles (120 kilometers) in a single glance. This ability allows it to capture the complete geography of the wave, and not just its trace along a narrow line, as previous instruments did. Oceanographers compare this advance to moving from tunnel vision to panoramic vision, finally offering a global understanding of the internal dynamics of these events.


The synergy between space-based measurements and existing networks, such as the DART buoys anchored on the ocean floor, was decisive. The latter provide accurate but localized data, like points on a map. SWOT's images, on the other hand, allow connecting these points to draw the true shape of the event. This complementarity validates a new investigation method for scientists.

Towards finer forecasting of coastal risks

This pioneering observation opens concrete perspectives for improving warning systems. The ability to visualize in detail and quickly the structure of a tsunami right from its formation in the open sea represents a considerable advantage. Propagation models could integrate this new data on wave dispersion, leading to more accurate arrival time and height forecasts for threatened coasts.

SWOT's contribution is not limited to wave physics alone. By allowing precise mapping of the deformation of the ocean floor that sourced the tsunami, the satellite helps to better understand the very mechanism of the earthquake that caused the phenomenon. This retrospective analysis enriches knowledge of subduction zones and their seismic potential, a key element for long-term risk assessment.

The study of the 2025 tsunami also allowed an instructive historical comparison with the great 1952 earthquake in the same region. The data suggests the fault had not released all its energy 73 years ago, contributing to the recent event.