Wave
Published on Nov 25, 2015
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PRESENTATION OUTLINE
A Tsunami is a a large seismic wave. A Tsunami is usually created by seismic plates shifting under the ocean, otherwise known as a earthquake.
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How are Tsunamis are Measured
Tsunamis have very short amplitudes (less than 1 meters) and really long wavelengths (hundred of kilometers).
They are measured by devices called tide pulses.
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Tide Gauges
"Tide gauges measure the height of the sea-surface and are primarily used for measuring tide levels. Most of the tide gauges operated by the Bureau of Meteorology's National Tidal Centre are SEAFRAME stations (Sea Level Fine Resolution Acoustic Measuring Equipment). These consist of an acoustic sensor connected to a vertical tube open at the lower end which is in the water. The acoustic sensor emits a sound pulse which travels from the top of the tube down to the water surface, and is then reflected back up the tube. The distance to the water level can then be calculated using the travel time of the-
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-pulse. This system filters out small-scale effects like wind-waves and has the capacity to measure sea-level changes within 1mm accuracy."
Source: Australian Government Bureau of Meteorology
http://www.bom.gov.au/tsunami/info
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