NASA Satellite Captures First High-Resolution Panorama of a Massive Pacific Tsunami
A powerful 8.8 magnitude earthquake near Russia's Kamchatka Peninsula in late July triggered a Pacific-wide tsunami, which was completely “tracked” from space in high resolution for the first time by a satellite dedicated to measuring ocean surface height.
A recent study published in *The Seismic Record* points out that the Surface Water and Ocean Topography (SWOT) satellite, jointly developed by the United States and France, recorded the first high-resolution space-based observational trajectory of a large tsunami triggered by this subduction zone earthquake, revealing a much more complex wave structure than previously expected, with energy constantly spreading and scattering across the vast ocean. Researchers believe this achievement will help humanity gain a deeper understanding of tsunami propagation mechanisms and improve assessments of potential impacts on coastal areas.
The study was completed by Angel Ruiz-Angulo of the University of Iceland and colleagues, who jointly analyzed sea surface height data acquired by the SWOT satellite with observations recorded by DART (Deep-ocean Assessment and Reporting of Tsunamis) buoys deployed along the tsunami’s propagation path. The results not only revealed details of the exceptionally complex tsunami waveform but also provided new constraints for reconstructing the rupture process of the 8.8 magnitude earthquake in the Kamchatka-Kurilea Trench, which occurred on July 29th and was the sixth largest earthquake ever recorded globally since 1900.
Ruiz-Angulo described the SWOT data as giving researchers a “new pair of glasses.” Previously, the scientific community relied primarily on DART buoys throughout the Pacific Ocean to obtain tsunami information, allowing them to “sample” tsunami signals only at limited locations across the vast ocean area. While other satellites can also observe changes in sea surface height, they can only “scan” a narrow line of the tsunami, even under ideal conditions. In contrast, each SWOT pass can acquire sea surface strips up to approximately 120 kilometers wide and characterize sea surface undulations with unprecedented high spatial resolution.
The SWOT satellite was launched in December 2022 and was jointly developed by NASA and the French National Centre for Space Studies (CNES). Its core mission is to conduct the first high-precision mapping of global surface water bodies and ocean surfaces. Ruiz-Angulo said that he and co-author Charly de Marez had been using SWOT data to study small-scale vortices and other structures in the ocean for more than two years and had not expected to “encounter” a large tsunami.
This observation also forced the scientific community to rethink the propagation characteristics of large tsunamis. Traditionally, the mainstream view has been that giant tsunamis with wavelengths much greater than the average ocean depth are “non-dispersive waves” and should be dominated by the overall waveform during transoceanic propagation, with energy not easily splitting into multiple wave groups. However, the data acquired by SWOT clearly showed the presence of dispersive effects: tsunami energy decomposed into multiple wave components during propagation and exhibited significant spatial dispersion and structural modulation.
After comparing numerical simulation results incorporating dispersive behavior with satellite and buoy measurements, the research team found that these “dispersive models” were significantly more consistent with real observations than simplified models using traditional assumptions. Ruiz-Angulo pointed out that this means that current tsunami numerical models are “missing something” in their physical mechanisms, especially in their characterization of the internal structure and energy redistribution of large-scale tsunami wave groups. He further speculated that these additional dispersive energies may lead to “trailing wave” modulation accompanying the main tsunami wave peak, which in turn may affect local wave heights and arrival times near certain coastlines, and these potential effects urgently need to be quantified and incorporated into future forecasting systems.
In this study, the team also compared SWOT and DART observations with previous tsunami forecasts based on earthquake source and surface deformation data. They found that at some deep-sea monitoring points, the predicted tsunami arrival times from traditional forecasts did not match the DART measurements: at one site, the modeled arrival time was too early, while at another, it was too late. To resolve this contradiction, researchers used a so-called “inversion” method to re-estimate the source rupture characteristics based on buoy measurements, and the results showed that the rupture zone of this 8.8 magnitude earthquake extended southward further than previously estimated, with a total length of approximately 400 kilometers, significantly longer than the previously estimated 300 kilometers.
Co-author Diego Melgar pointed out that since the 9.0 magnitude earthquake off the northeast coast of Japan in 2011, the seismological community has gradually recognized the high value of tsunami observation data for constraining shallow fault slip distributions. In recent years, researchers have been trying to integrate tsunami data such as DART with traditional seismic waves and surface deformation measurements, but in actual operations, this type of multi-source data coupling has not been fully normalized, one important reason being that the fluid dynamics models for simulating tsunamis and the solid earth models for simulating seismic wave propagation have significant differences in their physical and computational frameworks. He emphasized that this study once again shows that combining more types of observations is crucial for understanding source characteristics and tsunami behavior.
The Kamchatka-Kurilea Trench is a well-known area prone to strong earthquakes and tsunamis. As early as 1952, a 9.0 magnitude earthquake in the region triggered a Pacific-wide tsunami and directly spurred the establishment of the international tsunami warning system, which played a key role in warning and issuing alerts during this event in 2025.
Researchers said that as more satellite observation data like SWOT accumulates, it is expected to play a greater role in real-time or near-real-time tsunami forecasting in the future. Ruiz-Angulo said that if these results can be replicated in more actual events in the future, it will help prove to decision-makers and funders that investing in dedicated satellite observation capabilities has long-term value in enhancing global tsunami monitoring and warning levels.