Tsunami warning – Arugam bay- 12th September 2007- 6pm

The last major Tsunami warning we had was the night of 28th March 2005, 3 months after the devastating Tsunami occurrence of 26th December 2004, the effects of which are still apparent in certain parts of the Island.

Last week I was in Kandy up in the hill country; around 6pm I had a phone call from the Manager at Rocco’s telling me the Army were on the beach evacuating the area as a Tsunami had been predicted to hit the coast between 8pm & 9pm!

This was unusual as we have never had official warnings before, March 2005 I was warned by friends calling me from UK & Dubai saying a Tsunami was imminent! On that occasion it was up to us to evacuate the area, which we did in 20 minutes, everyone working together. That one was 8.9mg & 35km.

Underwater earthquakes were and are the cause of the Tsunami and the evenings warning.

After March 2005 I subscribed to the US Governments Earthquake centres warning system - http://earthquake.usgs.gov - You would be amazed at the number of earthquakes that take place around the world; record so far is 72 in a day including “aftershocks”.

You can even have the warnings sent to your mobile phone as I do, you can even set parameters of what warnings you get; where in the world, strength (magnitude or ‘mg’ to be correct), depth of epicentre, a Tsunami warning if deemed possible and all for free!

Duly I checked the messages, just as I was doing so it arrived, earthquake in Southern Sumatra, initially measured at 7.9 at a depth of 15km with an accompanying Tsunami warning, I was concerned.

Manager & staff headed for the higher ground, did not have to worry about guests they had left earlier in the day, we were empty at the time.

Main reason for my concern was it’s depth 15km is very shallow but compared with the “Big One” of December 2004, 9.2mg & 5km this could not have such a devastating impact. Nether the less a warning is a warning! & I am no expert, Zulu theory or no Zulu theory!

I scoured the Internet for reports of a wave forming; nothing at first but the report was revised to 8.2mg & depth 45kms much less worrying for us. I called friends in UK & Dubai to see what was being reported.

Indonesia dropped its Tsunami warning 1 hour after the “Quake” as no wave had come ashore. A 9ft wave, equal to a lot of the waves we get every day in Arugam Bay especially in “Surf season” (although they are very different forms of waves) was reported coming ashore in Padang & a 55cm one on the Cacaos Islands. Tsunami did arrive but small & not our shores. In fact the March earthquake did produce a 30cm & 35cm Tsunami to come ashore in Sri Lanka, just we did not notice.

8.2 is 10x less than 9.2 on the “Richter Scale” I am told, also being 9x deeper means there is a lot of “earth” to soak up the energy created before displacing the Ocean, forming a Tsunami wave.

In my surfing of the net I did discover the “Indian Ocean Tsunami Detection System” should be operational this month.
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Downside – all the mobile lines went dead after the warning was given, then landlines went, Internet & text messages were still getting through? I enquired with my supplier “Dialog” the first 3 times I posed the question the person or persons I asked put the phone own on me, when I eventually got through asking for a supervisor before posing the question, I was told “Network Issue” when I asked “what was the issue” phone went down on me again!?

The up side of all this is the fact we were given warning, 2 hours warning, enough time to be well out of any danger posed if a major event ever happened again, takes the panic out of it, meaning we can organise procedures and rest more securely in our hammocks. A great step forward in my opinion, well done to the authorities.

Steve (A little Knowledge is a dangerous thing) Jones

Warning notice as sent to e-mail or phone.

Magnitude 8.4
Date-Time

* Wednesday, September 12, 2007 at 11:10:26 UTC
* Wednesday, September 12, 2007 at 06:10:26 PM at epicenter

Time of Earthquake in other Time Zones
Location 4.520°S, 101.374°E
Depth 34 km (21.1 miles) set by location program
Region SOUTHERN SUMATRA, INDONESIA
Distances 130 km (80 miles) SW of Bengkulu, Sumatra, Indonesia
410 km (255 miles) SSE of Padang, Sumatra, Indonesia
620 km (385 miles) WNW of JAKARTA, Java, Indonesia
695 km (435 miles) SSW of SINGAPORE
Location Uncertainty horizontal +/- 6.1 km (3.8 miles); depth fixed by location program
Parameters Nst=286, Nph=286, Dmin=809.9 km, Rmss=1.11 sec, Gp= 29°,
M-type=moment magnitude (Mw), Version=V
Source

USGS NEIC (WDCS-D)

Event ID us2007hear