Thursday, October 01, 2009

Tsunami warning and response for Samoa

The Pacific Tsunami Warning Centre detected a magnitude 7.9 earthquake in the Samoa Islands region at 1748Z 29 September 2009. In response a Tsunami Warning and Watch was issued 16 minutes later at 1804Z (Bulletin 1). In all 11 messages were issued, the last being 0501Z 30 September 2009. The centre issued messages for both Hawaii and the Pacific.

Due to the closeness of the earthquake to Samoa and limitations in the technology available, the warning message was issued 5 minutes after the predicted arrival time of the Tsunami (1759Z) at the first population centre, Pago Pago in American Samoa.

The centre issues warnings to national authorities and there is then a delay while local authorities decide if, and how, to warn the public.
At best only 11 minutes warning could have been provided (assuming instantaneous detection, analysis and alert). Telecommunications systems can provide a warning within one minute.

The warning was also forwarded by email by UNESCO to the Interim Indian Ocean warning system mailing list. This message was dated Tue, 29 Sep 2009 18:04:43 GMT. It was received from UNESCO approximately three minutes later by the mail system and a summary by SMS via Vodafone Australia within one minute.

Samoa uses a system of sirens and church bells to the warn the population of Tsunami. The USA has a system of "NOAA Weather Radio" which issues automated warnings. There is a NOAA transmitter in American Samoa, located in Pago Pago.

During a visit to Samoa in 2005 to teach web design for UNESCO, I noticed that while a national digital telephone network had not yet been installed, there was a limited private GSM service (a similar service existed in Tonga). There were proposals for a GSM network in Samoa in 2007, but it is not clear how this has progressed. The significance of these networks is that they provide the SMS and SMS cell broadcast networks, which could be used to issue emergency warnings.

129/09/09 18:03Expanding Regional Warning
229/09/09 18:05Watch Statement
329/09/09 18:54Expanding Regional Warning Supplement
429/09/09 18:57Watch Supplement Statement
529/09/09 20:21Expanding Regional Warning Supplement
629/09/09 20:23Watch Cancellation Statement
729/09/09 21:34Expanding Regional Warning Cancellation
830/09/09 01:58Advisory Statement
930/09/09 03:03Advisory Supplement Statement
1030/09/09 03:57Advisory Supplement Statement
1130/09/09 05:01Final Advisory Statement

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