In late July, a massive earthquake occurred off the coast of Russia’s Kamchatka Peninsula, causing a tsunami to sweep across the Pacific Ocean. As the giant waves spread outward, NASA’s state-of-the-art satellite happened to be in the perfect position to observe the phenomenon in unprecedented detail.
The satellite, called the Surface Water and Ocean Topography (SWOT), has for the first time recorded high-resolution, wide-ranging images of large tsunamis caused by subduction-zone earthquakes, according to research published in 2017. Earthquake records.
What the scientists discovered was unexpected. Rather than traveling across the ocean as relatively simple waves, the tsunami exhibited a much more complex pattern in which the waves spread, scattered, and interacted over vast areas of the Pacific Ocean. The discovery could help researchers improve tsunami predictions and better understand potential risks to coastal areas.
Unusual sight of tsunamis across the Pacific Ocean
The tsunami was caused by a magnitude 8.8 earthquake that occurred on July 29 in the Kuril-Kamchatka subduction zone, where one plate is pushed beneath another. This earthquake was the sixth largest earthquake recorded in the world since 1900.
To study this phenomenon, researchers combined observations from the SWOT satellite with measurements from DART (Deep Sea Assessment and Tsunami Reporting) buoys located across the Pacific Ocean. These instruments are designed to detect subtle changes in sea level and provide early warning information in the event of a tsunami.
According to lead author Angel Luis Angulo of the University of Iceland, the satellite provided a dramatically different perspective from previous scientists.
“I think of SWOT data as new glasses,” Luis-Angulo said. “Previously, with DART, we could only see tsunamis at specific points across vast oceans. We have had other satellites before, but in the best-case scenario they could only see a thin line across the tsunami. Now, with SWOT, we can capture bands up to about 120 kilometers wide with unprecedented high-resolution sea level data.”
Satellite created for water research
SWOT was launched in December 2022 as a joint mission between NASA and the French National Center for Space Research. Its main goal is to create the first comprehensive global survey of Earth’s surface waters, tracking everything from rivers and lakes to ocean features.
Luis Angulo said he and co-author Charlie de Mares had spent more than two years analyzing SWOT observations of ocean processes such as small eddies and currents before this unique opportunity presented itself.
They said, “We had been analyzing SWOT data for over two years to understand various processes in the ocean, such as small eddies, but we never imagined that we would be lucky enough to capture a tsunami.”
Challenging long-held assumptions about tsunamis
One of the study’s most surprising findings concerns a concept known as dispersion.
Scientists have traditionally considered large tsunamis to be “non-spreading.” Because their wavelengths are much longer than ocean depths, researchers generally expect these waves to maintain a relatively consistent shape over long distances.
However, in a dispersive wave system, different parts of the wave move at slightly different speeds. This can cause the original wave to spread into a leading wave, followed by a series of trailing waves.
“The SWOT data from this event cast doubt on the idea that large tsunamis are non-dispersive,” explains Ruiz-Angulo.
When the researchers compared their observations with computer simulations, they found that the dispersion-inclusive model matched satellite measurements more closely than traditional tsunami models.
“The main implication of this observation for tsunami modelers is that something is missing in the models we were running,” Luis-Angulo added. “This ‘extra’ variation may represent that the main wave can be modulated by trailing waves as it approaches the coast. We need to quantify this excess dispersion energy and assess whether there are effects that have not been considered previously.”
Tsunami data reveals larger earthquake destruction
Tsunami observations also helped researchers better understand the earthquake itself.
Previous models based on seismic measurements and terrain deformation predicted tsunami arrival times, but they did not perfectly match what was recorded by the two DART gauges. One observatory detected the tsunami earlier than expected, while another recorded it later than expected.
To investigate this discrepancy, the research team used a technique called inversion, which estimates the characteristics of the earthquake that generated the tsunami by calculating backwards from the observed behavior of the tsunami.
Their analysis suggested that the earthquake rupture extended further south than previous studies had indicated. The area of destruction was approximately 400 kilometers (400 kilometers), significantly longer than the 300 kilometers estimated by previous models.
Study co-author Diego Melgar noted that tsunami observations are becoming increasingly valuable in understanding how large earthquakes cause destruction near the ocean floor.
“Since the magnitude 9.0 Tohoku-oki earthquake occurred in Japan in 2011, we realized that tsunami data had really valuable information for suppressing shallow slips,” Melgar said.
Why multiple data sources are important
After Japan’s devastating 2011 earthquake and tsunami, researchers began to focus on combining different types of observations when studying large earthquakes.
Melgar explained that incorporating DART buoy measurements into seismic analyzes remains difficult because the physics used to model ocean waves is different from the physics used to model seismic waves traveling through the Earth’s crust.
Since then, Melgar’s lab and others have been working on ways to include DART data in the inversion, but “the fluid dynamics models needed to model DART are very different from the seismic wave propagation models needed to model solid Earth data, so this isn’t always possible,” Melgar said. “But as we’ve shown here, it’s really important to mix as many types of data as possible.”
Improvements to future tsunami warnings
One of the largest tsunamis ever recorded in the Pacific Ocean occurred in the Kuril-Kamchatka Trench region. In 1952, a magnitude 9.0 earthquake in the same area triggered a massive tsunami, an event that ultimately prompted the creation of an international tsunami warning system.
This warning network later played a key role in issuing warnings throughout the Pacific during the 2025 tsunami.
As satellite technology continues to improve, researchers hope that observations like those collected by SWOT could one day become part of near-real-time tsunami prediction systems, providing faster and more accurate warnings to at-risk communities.
