Tsunami Speed Calculator
Tsunami speed and crossing hours from depth.
What it does
Tsunamis cross oceans at jet speeds because depth powers them: 4000 m of Pacific pushes waves near 713 km/h. Shelves slow the rush while piling its height.
The tool above takes ocean depth in meters or feet. It returns wave speed with crossing hours per 10,000 km.
The default 4000 m gives 198 m/s with 14 hours per ocean. The 1000 m case gives 99 m/s, and shelf shallows at 100 m give 31.
Tsunami warning programs teach v equals root(gd) for basin estimates, and oceanographic commissions repeat the depth speed link in education materials.
Speed estimates never trigger evacuations: shaking ground, loud ocean roar, and sudden sea retreat move feet first. Official alerts rule coasts; arithmetic only explains them.
How to use
- Pick meters or feet.
- Type the water depth.
- Read m/s first.
- Read km/h beside it.
- Read crossing hours last.
- Heed official alerts always.
Formula
- depth
- Ocean depth in m or ft.
- v
- Wave speed in m/s.
- g
- 9.81 m/s2 gravity.
NOAA tsunami programs teach the shallow water relation v = root(gd) for basin crossing estimates. UNESCO Intergovernmental Oceanographic Commission materials mirror the same depth speed link for warning education. Imperial inputs convert feet at 0.3048 first; outputs stay metric for ocean scale.
Worked example
Example: deep Pacific
Metric defaults: 4000 m depth.
- Ocean: 4000 m mean depth.
- Speed: root(9.81 x 4000) = 198 m/s.
- Convert: 198 x 3.6 = 713 km/h.
- Crossing: 10000 / 713 = 14 h per ocean.
- Shelf: 100 m slows to 31 m/s.
- Tool shows 198 m/s, 713 km/h, 14 h per 10,000 km.
Reference table
| Depth | Speed | Crossing |
|---|---|---|
| 4000 m | 198 m/s | 14 h |
| 1000 m | 99 m/s | 28 h |
| 100 m | 31 m/s | 89 h |
| 13123 ft | 198 m/s | 14 h |
Limits
- Ideal depth math only.
- Ridges and basins vary paths.
- Height needs separate models.
- Alerts rule, not arithmetic.
Common mistakes
- Reading offshore speed at beaches.
- Ignoring shoaling slowdown.
- Timing evacuations by math.
- Mixing depth units.
- Forgetting height grows ashore.
Try it yourself
Quick checks. Answers sit tucked under each question.
1000 m deep?
99 m/s with 357 km/h, 28 h per 10,000 km.
100 m deep?
31 m/s with 113 km/h at shelf shallows.
13123 ft deep?
Same 198 m/s and 713 km/h from feet.
0 m?
Zero depth holds no wave: enter depth above 0.
Questions
Wave formula?
Root of gravity times depth: root(gd). Deeper runs faster, shelves slow the rush.
Fast at beaches?
No, speed falls as depth shoals while height grows. The 198 m/s belongs offshore.
Crossing time?
About 14 hours per 10,000 km at deep speed. Real paths vary with ridges.
Only quakes?
Yes, earthquakes, landslides, and volcanoes all displace water into waves.
Warning signs?
Move inland or high on natural signs: shaking, loud roar, or sudden sea retreat.
Evacuate by math?
No, this paces waves for learning. Evacuation follows official alerts, never arithmetic.