A new look at tsunami physics from the Kamchatka M8.8 earthquake

The Surface Water and Ocean Topography satellite captured a 120 km (75 miles) wide swath of sea-surface height variations as the tsunami moved across the northwest Pacific.

This represented the first time a great tsunami generated by a major megathrust earthquake had been observed with such dense spatial coverage. Traditional altimeters only measure a thin line beneath the spacecraft, so their ability to capture tsunami structure has historically been limited.

The SWOT pass revealed a complex wavefield in which the primary wavefront was followed by a series of smaller, lower amplitude waves. These secondary waves showed signs of dispersion and scattering that had rarely been observed in past basin-wide tsunamis.

Ruiz Angulo of the University of Iceland described the effect as acquiring a new pair of glasses, referring to the ability to see patterns that were previously invisible using buoy-based networks.

Before SWOT, researchers relied heavily on DART buoys scattered across the Pacific Ocean. Each buoy can detect tsunamis with millimeter resolution, but they record data at isolated points and cannot visualize the shape of an entire wavefield.

The contrast between continuous swath measurements from SWOT and point-based DART records provided scientists with a unique combination of spatial and temporal insight.

The 2025 event was also the strongest earthquake since the launch of SWOT in 2022, providing the first opportunity to evaluate the satellite’s performance during a major subduction-zone earthquake.

As the wave moved beneath the orbiting instrument, the tsunami amplitudes recorded by SWOT aligned closely with those produced by numerical models that included dispersive physics.

A rupture more than 400 km (250 miles) long reveals its true scale

Early models based on seismic and InSAR datasets underestimated the length of the rupture at roughly 300 km (186 miles). When researchers compared that prediction to the tsunami measured by DART buoys, they found mismatches in arrival times.

Waves arrived several minutes early at two stations and more than ten minutes late at a third. This mismatch signaled that the initial rupture model did not fully represent the seafloor deformation that generated the tsunami.

Researchers performed a direct inversion of the DART records, reconstructing initial sea-surface displacement through a grid of Gaussian-shaped uplift elements spaced at roughly 0.3 degrees. The inversion covered a domain larger than the USGS model so that the solution could deviate naturally where needed.

When the inversion was completed, the results showed that the rupture extended at least 400 km (250 miles), with a peak uplift of about 4 m (13 feet) centered near 51 degrees north.

This pattern differed from the earlier USGS finite fault model, which had distributed slip in a narrower band. The inversion showed a broader southern extension and a higher uplift magnitude than previously assumed. However, the inversion lacked significant subsidence, which is expected in a pure thrust earthquake but was underestimated by the Gaussian parameterization. The team addressed this by blending the uplift field from the inversion with the subsidence field from the USGS model.

The combined model reproduced the DART observations with high fidelity. It corrected the timing errors and captured more realistic features of the negative pulse recorded at one of the buoys. This blended deformation pattern became the preferred source model for the 2025 Kamchatka earthquake tsunami.

The new rupture dimensions place the 2025 event alongside the largest megathrust earthquakes of the past century. It reactivated part of the same margin that broke in 1952, yet its rupture occurred farther down dip.

This depth difference reduced the amplitude of the tsunami compared to the catastrophic 1952 event, which produced runups exceeding 15 m (49 feet) along some parts of the Kamchatka coast.

A tsunami that broke the assumption of non-dispersive wave behavior

Tsunamis generated by large subduction earthquakes often contain wavelengths much longer than the ocean depth. Under these conditions, they are commonly treated as non-dispersive waves, meaning they should travel in a stable shape at nearly constant speed.

SWOT observations offered a clear counterexample. Behind the main crest, the satellite detected a sequence of trailing waves with varying amplitudes and spacing.

These secondary waves were not well reproduced by standard shallow water models. The team found that models including dispersive physics produced a better match. They employed a Boussinesq-type solver that incorporated higher-order terms to simulate shorter wavelength interactions. These dispersive models captured the breakup of the primary wavefront and the propagation of lower amplitude features that trailed the main tsunami.

Analysis of synthetic nadir tracks showed how the wave became increasingly disrupted as it moved northward. Between roughly 46 and 49 degrees north, dispersion became noticeable. North of 50 degrees, the wavefront split into multiple pulses due to interactions with the steep bathymetry of the trench and adjacent slopes. These transitions matched what SWOT observed more closely than nondispersive simulations.

The study concluded that short-wavelength features are probably generated near the source region where bathymetry changes abruptly. These features move away from the trench and require dispersive physics to be captured accurately.

Although the inversion used nondispersive Green’s functions, they remained valid for the first-arriving deep water wave. Later features were underrepresented due to the limited resolution of the inversion and the low number of buoys available.

This was one of the most compelling observations made by SWOT. It demonstrated that even tsunamis generated by very large earthquakes can contain a rich spectrum of wave energy, some of which can meaningfully influence coastal waveforms. This finding opens the door to improved hazard modeling that explicitly accounts for dispersive energy transfer across ocean basins.

An earthquake linked to the legacy of the 1952 Kamchatka event

The comparison between the 2025 rupture and the 1952 event reveals insights into the mechanics of the Kuril Kamchatka megathrust. Reconstructions of the 1952 slip pattern, based on historical records and tsunami deposits, indicate that shallow near-trench slip occurred along southern Kamchatka and the northern Kurils. These regions experienced a slip in the range of 9–15 m (29–49 feet).

Given a convergence rate of approximately 8 cm (3 inches) per year, the margin could have accumulated only about 5–6 m (16–20 feet) of slip since 1952. This suggests that the earlier earthquake did not fully release the available strain. The 2025 event likely consumed the residual slip left behind but did not propagate into the shallowest portion of the plate interface.

This depth difference explains why the 2025 tsunami, though recorded across the Pacific Ocean, was far smaller than the destructive 1952 tsunami. Near trench slip displaces more water because it lies closer to the ocean floor surface. A down-dip slip, while powerful, tends to raise and lower the seafloor over a smaller footprint. The 2025 rupture geometry, therefore, moderated the resulting tsunami impact.

For hazard models, the recurrence of two great earthquakes along the same margin in less than a century is a critical signal. Traditional seismic cycle models often assume long recurrence intervals for great earthquakes, but the Kamchatka records show that multiple events can occur on subcentury timescales. This is consistent with other fast-converging margins where incomplete strain release produces a sequence of large events instead of isolated ruptures.

The comparison also shows that megathrusts are capable of diverse rupture behaviors. Even within the same geological segment, the depth distribution of slip controls tsunami strength. This reinforces the need for models that account not just for magnitude but also for rupture geometry and depth when estimating coastal hazard.

A new role for satellite altimetry in tsunami science

The 2025 Kamchatka tsunami provided one of the clearest demonstrations of the scientific value of wide swath satellite altimetry. Prior events such as the 2004 Sumatra tsunami were observed by narrow-track satellites, but the low signal-to-noise ratio and thin spatial coverage limited their utility. SWOT changed this by offering broad and dense measurements across the wavefield.

Although SWOT data typically arrives with a latency of 5 to 10 days, it remains extremely useful for post-event modeling. Assimilating such data into hydrodynamic simulations can refine predictions of coastal impact during extended hazard responses. Even after the initial wave arrival, emergency managers and scientists often need updated models to prepare for later arriving waves or evaluate the risk of secondary events.

The study also showed that satellite altimetry readily complements the DART network. Where DART buoys offer precise timing and amplitude data at a few points, SWOT reveals the large-scale structure of the wavefield. Combined, these datasets form a powerful toolkit for characterizing tsunami sources in the days following a major earthquake.

Future missions with reduced latency or expanded spatial coverage may integrate directly into early warning systems. Even if real-time operations remain challenging, wide swath altimetry will likely become a central component of tsunami science. It offers the ability to observe wave patterns that traditional sensors cannot capture, improving both understanding and forecasting.

Researchers emphasize that the Kamchatka observations represent only the beginning. As SWOT continues to operate, more tsunamis will be recorded across different tectonic settings. Each new event offers an opportunity to refine models, improve inversion techniques, and test hypotheses about wave propagation across complex bathymetry.

References:

¹ SWOT Satellite Altimetry Observations and Source Model for the Tsunami from the 2025 M 8.8 Kamchatka Earthquake – Angel Ruiz‐Angulo et al. – GeoScienceWorld – November 26, 2025 – https://doi.org/10.1785/0320250037 – OPEN ACCESS

² Tsunami from Massive Kamchatka Earthquake Captured by Satellite – SSA – November 26, 2025

³ Powerful M8.8 earthquake and tsunami strike Kamchatka Peninsula, sixth strongest earthquake on record – The Watchers – July 30, 2025

Reet Kaur

I’m a science journalist and researcher at The Watchers, contributing to the Epicenter edition, where I cover peer-reviewed scientific research and emerging discoveries across Earth and space sciences. With a background in astronomy and a passion for environmental science, I’ve worked in shark and coral conservation in Fiji, conducting reef and shark-behavior research, contributing to mangrove restoration, and earning PADI Open Water and Coral Reef Certifications. I bring a blend of scientific rigor and storytelling to illuminate the discoveries shaping our planet and beyond.

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