Sri Lanka issues tsunami alert; no warning

Sept 13, 2007 (LBO) – Sri Lanka has issued a tsunami alert following an aftershock of a magnitude of 7.8 on the Richter scale in Indonesia at 05.19 am local time and asked people to await further instructions. Following are the message definitions used by the National Oceanic and Atmospheric Administration of the United States government which runs the Pacific Tsunami Warning Centre in Hawaii.

Tsunami Warning

The highest level of tsunami alert

Warnings are issued due to the imminent threat of a tsunami from a large undersea earthquake or following confirmation that a potentially destructive tsunami is underway. They may initially be based only on seismic information as a means of providing the earliest possible alert.

Warnings advise that appropriate actions be taken in response to the tsunami threat. Such actions could include the evacuation of low-lying coastal areas and the movement of boats and ships out of harbors to deep water. Warnings are updated at least hourly or as conditions warrant to continue, expand, restrict, or end the warning.

Tsunami Watch

The second highest level of tsunami alert.

Watches are issued by the TWCs based on