Tsunami Speed Calculator
Estimate a tsunami's propagation speed (m/s and km/h) from ocean depth. See why deeper water means faster waves, and add a distance for an arrival-time estimate.
Input
Enter the ocean depth and we estimate how fast a tsunami travels using the shallow-water equation v=√(g×depth) (g=9.8m/s²). The deeper the water, the faster it moves. These results are estimates only—for actual disaster decisions, always consult official sources such as your national meteorological agency.
Result
Tsunami propagation speed (estimate)
198.0m/s
In km/h, that isabout 713 km/h
Depth
4,000 m
Speed (km/h)
about 713 km/h
Arrival time over 100 km
about 8.4 min
The arrival time is a simple estimate assuming the tsunami travels 100 km in a straight line at constant speed. In reality, the speed changes continuously with the seafloor topography.
Propagation speed by depth (reference)
| Typical location | Depth | Speed (m/s) | Speed (km/h) |
|---|---|---|---|
| Nearshore / shallows | 10 m | 9.9 | about 36 |
| Shallow coastal waters | 50 m | 22.1 | about 80 |
| Continental shelf | 200 m | 44.3 | about 159 |
| Continental slope | 1,000 m | 99.0 | about 356 |
| Average open-ocean depth | 4,000 m | 198.0 | about 713 |
| Deep-trench class | 8,000 m | 280.0 | about 1,008 |
How it works
- Tsunami speed is calculated with the shallow-water equation v=√(g×depth), where g is gravitational acceleration, set to 9.8 m/s².
- The deeper the water, the faster a tsunami travels. In the open ocean at a depth of 4000 m it reaches roughly 700 km/h, while it slows sharply in shallow coastal waters.
- Speed is shown both in meters per second (m/s) and kilometers per hour (km/h). The conversion is 1 m/s = 3.6 km/h.
- Enter a distance to estimate the arrival time, assuming the wave travels that distance in a straight line at constant speed. Because real speed varies with seafloor topography, treat it as a reference value.
- The speed-by-depth table lets you compare estimated speeds across representative depths, from shallows to the deepest waters.
- Results are rough estimates only. For any disaster-related decision, always consult the latest information from official sources such as your national meteorological agency.
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