How is the height of a tsunami calculated?

The tsunami are anomalous sea waves mainly generated by underwater earthquakes of great magnitude, but also from Sottomarine landslides or volcanic eruptions. Their most deceptive feature is that, in open seaare almost imperceptible, with a height minimum (often less than a meter) but one speed Very high. It is only when they approach the coastand the seabed becomes less profound, that their energy is concentrated and the wave grows dramatically into height, transforming itself into a destructive force. The forecast of theirs height and theirs impact It is based on a combination of real -time data collected by advanced systems such as Boe Dart (Deep-Ocean Assessment and Reporting of Tsunamis) and the application of sophisticated numerical models. These models take into account the batimetry and of the coastal topography To simulate the propagation of the wave and estimate the height it will reach once you arrive on the ground, thus allowing you to emit prompt alerts.

How tsunami are born and because they are so dangerous

One tsunami was born when a huge mass of water is suddenly moved, usually due to a strong submarine earthquake (with magnitude greater than 7.0) which causes the lifting or lowering of the ocean backdrop. Also Sottomarine landslides or volcanic eruptions they can generate these waves. In the open sea, one tsunami is almost imperceptible: the wave is very long (even hundreds of kilometers) but its height is minimal, often less than a meter. His speedhowever, is impressive: it can reach that of a scheduled plane, too 800 km/h; It is the latter feature that makes it so insidious!

How to measure the height of a tsunami

THE’height of a tsunami varies drastically between the open ocean and the coast, and is measured with specific tools based on the context.

In open sea

The Boe Dart. These Boe I am a brilliant system: a sensor on the ocean backdrop notes the pressure variations caused by the passage of the wave of the tsunami. These data are transmitted via satellite to a buoy on the surface and then to the tsunami alert centers. The Boe Dart They are able to detect sea level variations of a few centimeters, essential to understand if an anomalous wave is actually a tsunami.

On the coast

When the tsunami approaches the coast, the seabed becomes less profound. The wave slows down drastically, but to keep its energy, his height It increases dramatically, transforming itself into a wall of water or in a series of waves that invade the mainland. Here height can reach Tens of meterslike i 30 meters recorded in some areas during the tsunami of 2011 in Japan.

How the height and impact of a tsunami predicts

The forecast of the height and impact of a tsunami is a complex and multidisciplinary process, which integrates data from different sources and the application of advanced scientific methodologies:

1. Seismic data: As soon as an earthquake takes place, the seismographers provide crucial information on magnitude, depth and epicenter. These data are the first alarm bell.
2. Numerical models: Scientists use complex mathematical models and computer simulations. These models “simulate” the propagation of the tsunami taking into account the batimetry (the shape and depth of the seabed) and the coastal topography. It’s like having one map 3D very detailed of the ocean and the coasts. By entering the earthquake data, the model can calculate how the wave will spread, how long it will take to reach different areas and, above all, how high it will be once reached the shore.
3. Boe Dart data: Real -time data from Boe Dart are essential to refine the forecasts. If a model predicts a wave of 50 cm In a point where there is a Boa Dart, and the buoy actually detects that wave, the forecast is confirmed and made more precise for the following areas.