A tsunami is a wave or waves caused by a large displacement of water. Tsunamis usually occur in large bodies of water such as oceans, but they can also occur in lakes. They can be formed as a result of large-scale natural events such as earthquakes, volcanoes or mass land movement.
Sea Level Station
A sea level station is an important instrument to measure a tsunami. It gives a clear and accurate indication of sea level changes. The system is linked with other stations within the area, enabling information to be gathered about the tsunami's size, its distance and the speed in which it is travelling. For analysis of nearby potential tsunamis, samples will need to be taken every second. For analysis of distant tsunamis, samples are taken every 15 minutes. This information is then sent to a central data collection centre.
Ocean Bottom Instrument
The Ocean Bottom Instrument measurement consists of a small device on the bottom of the ocean. These can be located kilometres away from the coast, connected only by a cable. These devices can be used to measure many different factors that could highlight the formation of a tsunami. Sensors can measure changes in seawater pressure, which means that there is greater activity on the surface. Monitors can also measure vibrations and deformation on the sea floor in the form of earthquakes or volcanic activity, which in turn could cause a tsunami.
Deep Ocean Assessment and Reporting of Tsunamis
The Deep Ocean Assessment and Reporting of Tsunamis, or DART, is an instrument that measures changes in sea level. The instrument is made up of a device on the ocean floor and a buoy on the water surface. The device is used to measure pressure changes on the sea floor, which are then transmitted to the buoy on the surface and on to a central control centre. This instrument is used for the early detection of tsunamis; it is capable of measuring sea level changes of 0.4 inches.
Modern technology has been developed that is capable of detecting tsunamis from space. Satellites are capable of measuring sea level change to an accuracy of 2 inches. However, the technology isn't currently suitable for use as an instrument to measure a tsunami because of the extensive distances involved. The satellite data takes a number of hours to reach the control centre, too long for an effective tsunami warning device.