Debris, damaged buildings and inundated land at a fishing port near Kesennuma after the 2011 tsunami.

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Preparing the 3D view

Preparing lighting and the first complete frame…

Model scale

Bathymetric relief ×20. wave and depth share the same vertical scale.

Propagation stage: 34.6 min · front 80.1 m/s at 655 m depth. Central crest reaches 100 m water at 97.6 min.

How to read these results

Two teaching stages: prescribed uplift, then a separate long-wave approximation. The dotted depth marker follows the wave packet; the chart enlarges displacement. No rupture dynamics, breaking, run-up or inundation are calculated.

Tsunami

Explain how seafloor displacement generates a tsunami and why its speed and height change as it enters shallow water.

Drag to rotate. Hold Ctrl and scroll to zoom, or pinch on a touch screen.

Why it happens

A tsunami has a long wavelength and travels faster in deeper water. As it crosses into shallower water, it slows and its amplitude can increase as energy is concentrated into a smaller depth.

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Kesennuma, Japan, after the 2011 Tōhoku tsunami. This aerial photograph records inundation damage; it does not show a breaking tsunami wave.

Try a comparison

Read the same front’s speed in deep and shallow water. Use the metre-scale chart to compare amplitudes.

Reading the result

This long-wave calculation ends offshore and excludes breaking, run-up and inundation on land.

A common misunderstanding

A tsunami and a storm surge are the same kind of coastal wave.

A tsunami is a sequence of long waves generated by rapid water displacement, such as seafloor movement or a landslide. Storm surge is an abnormal water-level rise driven mainly by storm winds and atmospheric pressure. Their causes, propagation and warning evidence differ.

Cases

Exam language

Tsunami

A series of long waves generated by rapid displacement of water, most commonly during a large undersea earthquake. In shallow water they slow and can grow in height. Tsunamis are not caused by the normal daily tides.

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Coastal damage after the 2011 Tōhoku tsunami. Run-up is the maximum vertical elevation reached by the water above a reference sea level; survey evidence is needed to attach a number to this photograph.

Shoaling

The change in a wave as it enters shallower water: it slows, its wavelength shortens, and its height may increase before breaking.

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A breaking wave at Porto Covo, Portugal. In shallow water a wave slows and steepens; its crest eventually breaks.

Storm surge

A rise in sea level above the expected tide, driven mainly by storm winds and atmospheric pressure. Coastal shape and water depth influence its size. Surge combines with tides and waves to determine coastal water levels and flooding.

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Bolivar Peninsula, Texas, September 2008. NOAA documented coastal damage from Hurricane Ike's storm surge.

Megathrust

A large, low-angle thrust fault at a subduction boundary. Sudden slip on its shallow offshore part can displace the seafloor and generate a tsunami.

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NASA ARIA observations of surface displacement following the 2025 Kamchatka megathrust earthquake. The coloured displacement field is measured evidence of movement, not a photograph of the buried fault.

Wavelength

The distance between corresponding points on successive waves, such as one crest and the next. A tsunami has a very long wavelength compared with ordinary wind waves. Its wavelength changes as speed and water depth change during propagation.

Drawdown

A lowering of water level. In the tsunami lab it means the withdrawal of the sea before some waves; many tsunami arrive without this warning. Groundwater drawdown means a lowered water table or pressure level.

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Groundwater hand pump at Perambalur, India. Abstraction removes water from an aquifer; pumping may lower the water level around a well, which is measured below ground.

Run-up

The maximum elevation reached by a wave above a specified reference sea level as it moves onto land; distinct from inland inundation distance.

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