How is a buoy used in a tsunami mitigation system?

Answer 1

First off, it's important to be clear about the fact that tsunamis themselves can not generally be mitigated or reduced in intensity. Ocean Data Aquisition System (ODAS) buoys comprise part of a tsunami early warning system. The earlier the tsunamis are detected, the earlier that the population and infrastructure on threatened Coastlines can be warned, hopefully lessening damage and loss of life. Tsunamis are formed as the result of seismic events which transfer energy to the surrounding sea. Thus, the earliest means of detecting them is through seismic (i.e. earthquake) measurement. A particular seismic event is a good predictor of an associated tsunami, depending on its intensity and the location of its epicenter. ODAS buoys supplement this by measuring characteristics of the sea waves which are generated. An ODAS buoy can measure the wave height (3d position at any given time), and also the period between consecutive waves. This provides a good indication of both the destructive potential of a particular wave train, and its propagation time (i.e. how long the waves will take to reach land). This information is invaluable if it can provide advance notice to a threatened area. Other ODAS capabilities may include acoustic measurement (direct observation of seismic activity), sea salinity, temperature, wind direction and velocity, current speed and direction, etc., for weather monitoring and prediction. At sea, a seismic event which generates a tsunami may not even be noticeable from a seaborne observer, since the resultant wavelength is generally very long. Imagine floating in a small boat while a 20 meter high wave passes beneath you - if the wavelength is short, such a wave would obviously be devastating. If, however, a wave this high took a full minute to pass beneath you, your change in elevation would occur so slowly that it may not even be noticed. Long wavelength, high energy waves like this are typical of tsunamis. Thus, the ODAS buoys provide a means of detecting and describing them well out at sea - hopefully in sufficient time to prepare for their landfall.

Answer 2

Buoys in a tsunami mitigation system are placed in the ocean to detect changes in water level that could signal an incoming tsunami. They relay this data to monitoring stations, allowing for early detection and timely evacuation warnings to be issued to coastal communities in the path of the tsunami.