Since 1946, the tsunami warning system has provided warnings of potential tsunami danger in the pacific basin by monitoring earthquake activity and the passage of tsunami waves at tide gauges.↵
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However, neither seismometers nor coastal tide gauges provide data that allow accurate prediction of the impact of a tsunami at a particular coastal location.↵
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Monitoring earthquakes gives a good estimate of the potential for tsunami generation, based on earthquake size and location. but this gives no direct information about the tsunami itself.↵
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Tide gauges along coasts provide direct measurements of the tsunami, but local factors such as the depth and shape of ocean floor as well as the shape of the coastline can influence the impact of a tsunami.↵
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That makes it difficult to use information from one location to make predictions about a tsunami's impact in another.↵
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Partly because of these data limitations, warning systems have often issued false alarms.↵
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in these cases, the tsunami that arrived was too weak to cause damage.