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L

Leading wave

First arriving wave of a tsunami. In some cases, the leading wave produces an initial depression or drop in sea level, and in other cases, an elevation or rise in sea level. When a drop in sea level occurs, sea level recession is observed.

Local tsunami

A tsunami from a nearby source for which its destructive effects are confined to coasts less than 1 hour tsunami travel time, or typically within about 200 km from its source. A local tsunami is usually generated by an earthquake, but can also be caused by a landslide or a pyroclastic flow from a volcanic eruption. Over history, 90% of tsunami casualties have been caused by local tsunamis.

3-story buildings overturned during 11 March 2011 Japan tsunami. Onagawa, Japan. Photo courtesy of ITIC.

Tsunami flow depths exceeding 10 m and flow velocities over 6 m/s overturned and dragged 3-story buildings as much as 50 m during the 11 March 2011 Japan tsunami. Onagawa, Japan. Photo courtesy of ITIC.

Low water

The lowest water level reached during a tide cycle. The accepted popular term is low tide.


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