Thailand Issue, Then Cancel, Tsunami Warning

[The_Other_Mac]

Why don't the scientists & officials, who are supposedly in the know, warn people based on real changes in  water density and actual wave height at islands along the way, instead of everytime there is an earthquake nearby?  NOT ALL UNDERWATER EARTHQUAKES CAUSE TSUNAMIS, indeed there are underwater quakes all the time, but the last tsunami anywhere near the size that hit Sri Lanka & Thailand hadn't been seen anywhere on Earth for 40 years before.  Warning people everytime there is an underwater Earthquake is like warning pedestrians everytime a car is coming that an accident is coming.  Only underwater Earthquakes with a particular type of plate motion (up & down, as opposed to side to side) create Tsunamis.  Also, the intensity has quite a bit to do with it, as the destructive tsunami was caused by an approx 9.0 quake, which is 100 times stronger than a 7.0 quake. 

Giving people warnings that turn out to be false is as bad as giving no warnings at all, because people will come to believe the warnings are never right, and eventually will not head them, like the Aesop fable of "The Boy Who Cried Wolf!"

<{POST_SNAPBACK}>

Lack of islands along the way.

The only islands relevant to last night's tsunami were the Similan group, and they were indeed in touch with the National Park headquarters on Koh Mieng. As far as I could understand the Thai TV, it would provide a few minutes advance warning for the mainland, but not enough to evacuate entire coastal areas or get the message to remote villlages in the middle of the night. Not everyone sleeps in a Phuket resort.

I don't know what the threshold or guidelines are for declaring an alert in Thailand, but after last December, various sources stated that 7.0 might cause a tsunami depending on other conditions. Last December's quake was initially announced by USGS as 8.0, wrong by an entire factor of 10. Furthermore it disturbed the whole region enough that previous averages ("40 years") don't really apply anymore and please note, statistics do not predict individual events.

The guy now in charge of issuing a warning, Plodprasop, had previously been removed from the position for "irresponsibly" issuing a tsunami alert, a few years before. At the time, businesses complained that he needlessly caused panic. That's why no alert was issued on Dec. 26th. Last night I guess they were erring on the side of caution, can't imagine why.

Incidentally, there was no alert for the 5.6 aftershock in the same place this morning.

[george]

Update:

Thailand's tsunami drill praised

BANGKOK: -- After several practice runs and one "live" alert, Thailand's tsunami warning system swung smoothly into action following Sunday's Andaman Sea quake, but coastal residents said the still ad hoc set-up needs fine tuning.

"I would give them about eight out of ten," said Frank Dreist, general manager of the 273-room Kata Beach Resort on Phuket, the tsunami-hit southern resort island where Thailand has worked hardest to build an effective alert network.

"The night manager was phoned by the authorities about 15 to 20 minutes after if happened and the police were very quick to get out with loudspeakers," he said.

"We immediately evacuated the ground floor, moving guests to higher floors or the roof."

The U.S. geological survey measured Sunday night's (1542 GMT) quake in India's Andaman and Nicobar Islands at 7.0 on the Richter scale, just below the 7.5 reading experts say is needed to generate a tsunami.

The Dec. 26 wave, which left 227,000 dead or missing around the Indian Ocean, was triggered by a 9.15 magnitude earthquake. Thailand, which has been promoting its early warning capabilities as a tourist confidence booster, still chose to issue an alert, interrupting programming on all television networks to tell those in southwestern coastal areas to evacuate.

On the island of Phi Phi, famed as the utopian backdrop to cult Leonardo di Caprio backpacker movie "The Beach", the message came through on TV, but a jammed mobile phone network meant it was difficult to pass on, residents said.

"The warnings were mostly in Thai, so didn't help tourists that much. But it definitely helped to have clarification if this was a real warning or just another earthquake," said Andrew Hewett, a British dive operator.

"Quite a lot of people went to higher ground and slept on the mountain, but those with experience of last time went only as high as needed. Some just slept on the roof," he said.

Sirens installed on the island's now-pristine beaches are due to be tested this week, which should make the mobile phone network problem less of an issue, he said.

Risk of crying wolf

Prime Minister Thaksin Shinawtra said the warning system, which uses everything from television, radio and mobile phone text messages to sirens and policemen with megaphones, was set for 7.0 Richter quakes or bigger.

He acknowledged the risk of "crying wolf" too often, but said the greater margin of error was justified because monitoring networks were not perfect.

"If we ran too many times, the concern is that people might be less alert in the future when the real tsunami comes. People might treat them as more false alarms," Thaksin told reporters.

"But when we have inadequate equipment, there's no harm issuing an alert. It's better to err on the side of safety rather than make a wrong decision," he said.

Sunday's alert was the second since Dec. 26. in Thailand, where 5,395 people, including 1,953 foreigners, were killed. An 8.7 magnitude quake off the northern coast of Sumatra on March 29 triggered a coastal evacuation order but no tsunami.

"Last night was better than the one before. People panicked less and they knew what to do and where to go," said Suvit Othong, superintendent of Phuket police, although he admitted roads away from beach areas were clogged with traffic.

--Reuters 2005-07-26

[hellohello]

Did anyone else feel the earthquake LAST NIGHT it struck about 3 am?

it was a 5.6, again from the NICOBAR ISLANDS. I'm in Krabi and our house was swinging!

[LadyinRed]

And finally, I thought tsunami warning system consists of a bit more than just seizmograph and a siren. I would have thought that you put detectors into the sea, 50, 100, 150, 200, ... km from the shore so you know what's really coming and at what speed. I think that if a couple more fake alarms like this happen, people will just put earplugs in the next time alarm goes off...

<{POST_SNAPBACK}>

Well said tomazbodner.

Can anyone explain the reason for different reports of richter scale on 26 Dec earthquake? It seemed to start at 7.something and goes up to 8.something in the span of 24 hours.

[tracer]

Thailand averts second tsunami 

The centre warned in an urgent statement broadcast live on TV pool that the new tsunami, if took place, was forecast to hit Phuket's Kalon Beach at around 0:12 a.m. and other areas in the tsunami-prone provinces from around 0:13-1.30 a.m.on  Monday.

<{POST_SNAPBACK}>

Living in kamala in Phuket I was called at night by friends and received sms's etc so had a look.

1. not ONE siren, no warning over speakers or whatever. Normally they can play music, explain farang football and politics and not least of all religion, but they were QUIET.

2. Didnt see one policeman (heard they were on the beach) and in a bar with TV all one saw was some Thais talking about Tsunami's, showing films of december and music with Thai songs and were surprised the next morning there had been a fuss..

Anyway to be sure I went upto Patong Hill where there is a small karaoke and waited out what never came. Many people slept through the whole thing ( as I did myself a few months ago).

Later on internet when I got back 1.30 to the vilage I dove into a bar with PC's, looked up CNN and the eartquake center, and it was quite clear that 1) it wasnt powerful enough and 2) acc to CNN the warning was withdrawn very quicky.

In Patong several guesthouses lost customers who had enough...

[tracer]

9 on the richta scale is hundreds of times stronger than a mere 7, The Thai goverment needs to get this exactly right.!!!

<{POST_SNAPBACK}>

Yes, but how many Thai understand the logarithmic nature of the Richter scale???????????????????

<{POST_SNAPBACK}>

I don't think you understand the whole thing. All you do is put Thai people down.

<{POST_SNAPBACK}>

Its not the Thais Job to understand the logarithmic scale, however it is the Job of Thai Goverment Officials to employ people who do understand it, and to issue the appropriate warnings, Surely..?

<{POST_SNAPBACK}>

And I thought that Richter used a 100log scale, not a 10log....

Whatever, it was a 9.6 or 9.7 in December

[tracer]

Quote

Now the problem - Kata has no warning system. To get from there to high ground, you need to pass the entire Karon beach, which is a long way right next to the sea, so if the wave needed an hour to get there, by the time you get the message, you'll most likely get wet.

Hotel staff doesn't care about any warnings from anyone and couldn't bother waking up the guests.

EOQ

To get out of Kata quick all you need is 300 m to main road between Patong and Chalong and drive maybe 1 km up the hill to Chalong, park yourself in one of the many food places above waterlevel. Why do you want to goto Patong???

Blocked anyway and a lousy road.In Kamala to get to the assigned high places you have to drive IN THE DARK over gravel paths etc, much easier as I couldnt find anyone to tell me where it was to dive up the hill to Patong. No use going to Surin as on the way there its difficult to park and no place to sit....

[tracer]

Quote

How much bigger is a magnitude 9.7 earthquake than a 6.8 earthquake?

A magnitude 9.7 earthquake is 794 times BIGGER on a seismogram than a magnitude 6.8 earthquake. The magnitude scale is logarithmic, so

(10**9.7)/(10**6.8) = (5.01*10**9)/(6.31*10**6) = .794*10**3 = 794

OR

= 10**(9.7-6.8) = 10**2.9 = 794.328

Another way to get about the same answer without using a calculator is that since 1 unit of magnitude is 10 times the amplitude on a seismogram and 0.1 unit of magnitude is about 1.3 times the amplitude, we can get,

10 * 10 * 10 / 1.3 = 769 times [not exact, but a decent approximation]

The magnitude scale is really comparing amplitudes of waves on a seismogram, not the STRENGTH (energy) of the quakes. So, a magnitude 9.7 is 794 times bigger than a 6.8 quake as measured on seismograms, but the 9.7 quake is about 23,000 times STRONGER than the 6.8! Since it is really the energy or strength that knocks down buildings, this is really the more important comparison. This means that it would take about 23,000 quakes of magnitude 6.8 to equal the energy released by one magnitude 9.7 event. Here's how we get that number:

One whole unit of magnitude represents approximately 32 times (actually 10**1.5 times) the energy, based on a long-standing empirical formula that says log(E) is proportional to 1.5M, where E is energy and M is magnitude. This means that a change of 0.1 in magnitude is about 1.4 times the energy release. Therefore, using the shortcut shown eartlier for the amplitude calculation, the energy is,

32 * 32 * 32 / 1.4 = 23,405 or about 23,000

The actual formula would be:

((10**1.5)**9.7)/((10**1.5)**6.8)

= 10**(1.5*(9.7-6.8)) = 10**(1.5*2.9) = 22,387

This explains why big quakes are so much more devastating than small ones. The amplitude ("size") differences are big enough, but the energy ("strength") differences are huge. The amplitude numbers are neater and a little easier to explain, which is why those are used more often in publications. But it's the energy that does the damage.

EOQ

OK, hope this sorts out what a Richter is.....

I copied it from an expert website, easier then doing the calculations!!

And by the way we had a 9.6 to 9.7 in december and this last one I seem to remember was less then 7 so numbers are kind of applicable to comparing the July and December earthquakes.....

Not 2 richter less but about 23000 times less power.....

Note that I have seen texts putting energy for safety purposes higher than whats mentioned above.