Observations made by a satellite operated by the US and French space agencies shortly after a strong earthquake struck off Russia’s Kamchatka Peninsula last year are giving scientists a better understanding of how tsunamis originate and propagate.
The researchers said the findings might help improve understanding of future tsunamis and earthquakes, particularly near ocean trenches.
The strongest tsunamis often are generated by such quakes.
Photo: Reuters
The magnitude 8.8 quake struck on July 29 last year, triggering a tsunami that spread across the Pacific Ocean. Tsunamis — a series of extremely long and powerful ocean waves — are typically caused by large movements of the seafloor that push water up or down during earthquakes.
The NASA-CNES Surface Water and Ocean Topography, or SWOT, satellite made its observations within 70 minutes of the start of the earthquake.
It observed not only the leading wave of the tsunami, but also a distinct pattern of smaller waves trailing behind it.
Such wave patterns had long been predicted in computer models and theoretical studies, but had been difficult to confirm with real-world observations, the researchers said.
“I believe SWOT represents a new lens for observing and studying tsunamis and their generation,” said Ignacio Sepulveda, a professor of coastal engineering at San Diego State University and lead author of “SWOT detects dispersive tsunami tied to a near-trench source in the 2025 Kamchatka earthquake,” an article published in the journal Science on Thursday.
“It is also likely to improve our understanding of the physical mechanisms that generate tsunamis, including earthquakes,” Sepulveda said.
Traditional deep-ocean pressure sensors and other satellites have limitations in coverage and measurement, making it difficult to capture the full structure of the waves, especially near trenches, the researchers said.
SWOT scans a wide swath of the ocean, producing 2D maps of sea surface height. This allows scientists to see the shape, direction and spacing of tsunami waves in much greater detail.
Tsunamis are among the strongest and most destructive natural forces, with powerful waves radiating from a point of origin outward in all directions. The waves can cause damaging and deadly coastal flooding.
The Kamchatka tsunami did not cause significant loss of life, but others have caused huge death tolls such as the 2004 Indian Ocean tsunami that killed about 230,000 people.
The tsunami last year originated within about 10km of the trench, the researchers said.
The location could not previously be determined using traditional land-based instruments or sparse sensors on the seafloor alone.
The researchers said that when earthquake-caused movement extends close to the trench, it can generate shorter waves that travel more slowly and spread out, forming a trailing pattern behind the main tsunami front.
The behavior means that different parts of the wave move at different speeds, with longer waves moving more quickly and leading while shorter ones lag behind.
The study also showed that the strength of the trailing waves increases when earthquake movement extends closer to the trench, suggesting the waves are linked to where and how the tsunami was generated near the trench.
“This opens a new window to understand in a better way what happens with earthquakes and tsunamis near the trench,” Sepulveda said, referring to SWOT observations. “In the future, this knowledge will allow us to improve models we use to evaluate tsunami hazards in coastal communities and make them more resilient.”