Tsunami Wave Speed

This formula estimates how fast a tsunami travels when it is in deep enough water to behave like a shallow-water wave. The key idea is that the wave speed depends mainly on the water depth: deeper water lets the wave move faster because the disturbance involves the whole water column, and gravity is the restoring force that tries to flatten the wave. It does not depend on the wave’s height or period in this approximation, which is why tsunamis can cross oceans so quickly.

Use this when estimating tsunami travel speed over the open ocean, or more generally for shallow-water waves where the wavelength is much larger than the water depth. It is useful in geoscience, hazard planning, and rough arrival-time calculations.

• Using the formula for ordinary wind-driven ocean waves, which depend on wavelength and are not shallow-water waves
• Forgetting to keep units consistent, especially using depth in kilometres instead of metres
• Thinking the formula gives wave height or impact strength rather than travel speed