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<p>An Mw 8.8 earthquake on 29 July 2025 generated a tsunami near the Kamchatka Peninsula. The interferometric Synthetic Aperture Radar (InSAR) satellite Surface Water and Ocean Topography (SWOT) produced images of sea surface height anomalies (SSHAs) approximately 600&#xa0;km from the epicenter about 70&#xa0;min after the earthquake. The image shows concentric dispersive tsunamis as SSHA and we inverted the observed SSHA for the earthquake fault slip distribution using dispersive tsunami modeling. We adopted the Normalized Cross-Correlation (NCC) to determine the tsunami start time and to assess the agreement between the observed and synthetic images. The obtained slip distribution revealed a large slip of approximately 16&#xa0;m in the southern region concentrated near the trench axis. This suggests a localized rupture extending to the trench axis at the shallowest part of the plate interface along the Kamchatka trench, where the Pacific Plate subducts beneath the North American Plate. The estimated magnitude of Mw 8.8 is consistent with the United States Geological Survey (USGS) estimate. Synthetic tsunami waveforms at the three nearest tsunami stations in the deep sea showed good agreement with the observed sea level time series. For the first time, we demonstrated that the earthquake slip can be estimated solely from SWOT satellite tsunami imagery. Our slip model revealed local spatial variability in the slip distribution that far exceeds the slip expected from plate motion and recurrence intervals. Such unexpectedly large fault motion that directly impacts the tsunami hazard forecast can be estimated quickly if SWOT-like imagery becomes available in near real time.</p> Graphical Abstract <p></p>

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The slip distribution of the 2025 Kamchatka earthquake determined from SWOT satellite dispersive tsunami images

  • 期刊论文

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  • 发表日期：

    2026年8月4日

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  • Kiyohiro Ishijima,
  • Shingo Watada

摘要

An Mw 8.8 earthquake on 29 July 2025 generated a tsunami near the Kamchatka Peninsula. The interferometric Synthetic Aperture Radar (InSAR) satellite Surface Water and Ocean Topography (SWOT) produced images of sea surface height anomalies (SSHAs) approximately 600 km from the epicenter about 70 min after the earthquake. The image shows concentric dispersive tsunamis as SSHA and we inverted the observed SSHA for the earthquake fault slip distribution using dispersive tsunami modeling. We adopted the Normalized Cross-Correlation (NCC) to determine the tsunami start time and to assess the agreement between the observed and synthetic images. The obtained slip distribution revealed a large slip of approximately 16 m in the southern region concentrated near the trench axis. This suggests a localized rupture extending to the trench axis at the shallowest part of the plate interface along the Kamchatka trench, where the Pacific Plate subducts beneath the North American Plate. The estimated magnitude of Mw 8.8 is consistent with the United States Geological Survey (USGS) estimate. Synthetic tsunami waveforms at the three nearest tsunami stations in the deep sea showed good agreement with the observed sea level time series. For the first time, we demonstrated that the earthquake slip can be estimated solely from SWOT satellite tsunami imagery. Our slip model revealed local spatial variability in the slip distribution that far exceeds the slip expected from plate motion and recurrence intervals. Such unexpectedly large fault motion that directly impacts the tsunami hazard forecast can be estimated quickly if SWOT-like imagery becomes available in near real time.

Graphical Abstract