2 7-Magnitude Quakes Strike NE Myanmar; No Tsunami

[TotallyOz]

Two strong earthquakes struck northeastern Myanmar less than a minute apart Thursday night. They could be felt as far away as Bangkok, but a tsunami was not generated.

 

The first 7.0-magnitude quake was just six miles (10 kilometers) deep, according to the U.S. Geological Survey. It was followed by another of the same strength but far deeper: 140 miles (230 kilometers).

 

The quakes struck along Myanmar's borders with Thailand and Laos, about 70 miles (110 kilometers) from the northern Thai city of Chiang Rai.

 

Buildings swayed in Bangkok, 500 miles (800 kilometers) south of the epicenter.

 

The Pacific Tsunami Warning Center says it was located too far inland to create a destructive wave.

 

 

 

 

http://abcnews.go.com/International/wireStory?id=13211209

 

 

 

[Bob]

I was laying on the couch here in Chiangmai when all of a sudden everything started shaking and moving a little. The mild shaking lasted about 10 seconds and wasn't bad enough to convince my lazy ass to run outside.

 

According to the news (CNN and the Nation), the epicenter was about 200 kilometers north of Chiangrai....so I'm wondering if there might be some actual damage around the Maesai area. Guess we'll hear about that on tomorrow's news.

[Guest fountainhall]

I remember after the December 2004 Indonesia earthquake and tsunami, Thailand changed its earthquake zones. Bangkok became an earthquake possible zone. I wonder how many condo owners now add earthquake insurance to their policies?

[Guest]

So what magnitude of earthquake do they think could occur in Bangkok?

Actually, we do have small earthquakes in the UK, but these are very rare and of low magnitude. Maybe 2 on the Richter scale, so they are pretty much irrelevant.

I guess Bangkok is somewhere between the UK & Tokyo in terms of risk?

[Guest fountainhall]

So what magnitude of earthquake do they think could occur in Bangkok?

I don't think anyone can predict the magnitude of earthquakes. More important for building codes and emergency procedures is location close to fault lines in the earth's crust. Bangkok has two main problems in this respect -

 

1. there is an active fault line less than 200 kms away under Kanchanaburi Province;

 

2. Bangkok's subsoil is almost identical to that under Mexico City. Mexico had no history of earthquakes in recent centuries until the huge 8.1 'quake' in 1985.

 

Either of these conditions is inevitably cause for concern.

 

Our capital city is only 200km away from an active fault line in Kanchanaburi province.

Seismologists used to believe that Bangkok was free from the risk of earthquakes. Yet, the deadly earthquake in Mexico City in 1985 made them change their minds.

 

Like Bangkok, Mexico City did not have a record of earthquakes in modern history. But when the 8.1 magnitude earthquake occurred in 1985 only 400km from the heart of Mexico City, many buildings were brought down, particularly those built on soft clay.

 

Geographically, Mexico City is a twin to Bangkok. Both have the same soil structure and are located a few hundred kilometres away from active faults. Mexico City sits on soft clay in an area that used to be a huge lake. Bangkok and its vicinity, meanwhile, was once under the sea.

 

Local seismologists are worried that if an earthquake with a magnitude of 8 were to occur along the fault line in Burma or a magnitude 7 earthquake were to happen in Kanchanaburi province, Bangkok would be jolted hard, heavily damaging buildings standing on soft clay areas . . .

http://www.bangkokpost.com/print/31596/

 

Bangkok to be declared an earthquake risk zone

15 September 2007 (channelnewsasia)

 

BANGKOK : Thailand is drafting regulations to declare Bangkok an earthquake-prone zone after the capital felt the effects of a recent 8.4-magnitude quake in Indonesia, a government official said Saturday.

 

The new law would require all new tall buildings in Bangkok and surrounding provinces to be quake-proof. It has been drafted by the interior ministry and is currently being reviewed by Thailand's top legal experts.

 

"Bangkok's soil is soft and it generates more tremors," said Worawoot Tantiwanit, a senior official with the mineral resources department. "In the most recent major earthquake in Indonesia on Wednesday, people in high rise buildings in Bangkok clearly felt the effects," he told AFP.

 

Worawoot said his department was currently studying the risks posed to the capital by three fault lines within a 100-kilometre (62-mile) radius of Bangkok.

 

Ten of Thailand's 76 provinces are currently listed as earthquake-risk zones, mostly in the northwest. The proposed law would add 12 central and southern provinces to the list.

http://environmentalnews.blogspot.com/2007/09/bangkok-to-be-declared-earthquake-risk.html

[Guest voldemar]

I don't think anyone can predict the magnitude of earthquakes. More important for building codes and emergency procedures is location close to fault lines in the earth's crust. Bangkok has two main problems in this respect -

 

1. there is an active fault line less than 200 kms away under Kanchanaburi Province;

 

2. Bangkok's subsoil is almost identical to that under Mexico City. Mexico had no history of earthquakes in recent centuries until the huge 8.1 'quake' in 1985.

 

Either of these conditions is inevitably cause for concern.

 

 

http://www.bangkokpost.com/print/31596/

 

 

http://environmentalnews.blogspot.com/2007/09/bangkok-to-be-declared-earthquake-risk.html

What about Pattaya? With a poor quality of construction I can only imagine what may happen with all these high rise condos even in case of moderate earthquake...

[Guest fountainhall]

What about Pattaya? With a poor quality of construction I can only imagine what may happen with all these high rise condos even in case of moderate earthquake...

Not sure about Pattaya, but when the Indonesian 'quake' was taking place, some high-rise buildings in Bangkok swayed quite violently. Guests at the Banyan Tree on Sathorn were evacuated, as were residents in a much more square-shaped condo building (and therefore, I'd have thought, a much more stable one) behind it. The epicentre of that 'quake' was much further away than the recent ones in Myanmar. Mind you, it was a great deal more violent. So, I'd guess that Pattaya must have been similarly affected.

[Guest voldemar]

Not sure about Pattaya, but when the Indonesian 'quake' was taking place, some high-rise buildings in Bangkok swayed quite violently. Guests at the Banyan Tree on Sathorn were evacuated, as were residents in a much more square-shaped condo building (and therefore, I'd have thought, a much more stable one) behind it. The epicentre of that 'quake' was much further away than the recent ones in Myanmar. Mind you, it was a great deal more violent. So, I'd guess that Pattaya must have been similarly affected.

If you are talking about 2004 tsunami earthquake, I was in Tarntawan place when it happened and it was barely noticed (but still noticed). Next day I was in Pattaya and certainly tsunami simply did not happen over there (understandably though cause it is a different ocean so to say). In any case, I hope Pattaya is safe cause otherwise I have no place to go. On the second thought, Singapore seems to never had any kind of natural disaster...

[Guest]

As far as I know, the nearest fault major fault line to Thailand runs through the Andaman islands.

 

Wouldn't Mexico city be closer to the fault line that runs down the west coast of the USA?

[Guest fountainhall]

I think you are correct about the Andaman fault line being the closest, and that seems to be a good 700 kms and more from Bangkok, whereas the epicentre of the Mexico City quake was half that distance away. On the other hand, a quake of 8.1 on the Andaman fault could certainly have quite devastating effects on Bangkok.

 

The 1985 Mexico City earthquake, a magnitude 8.1 earthquake (was) located off the Mexican Pacific coast, more than 350 km away, but due to strength of the quake and the fact that Mexico City sits on an old lakebed, Mexico City suffered major damage.

http://en.wikipedia.org/wiki/1985_Mexico_City_earthquake

 

On the other hand, with 13 active fault lines running under Thailand, there is surely the potential for major damage since Thailand's building codes have only recently been strengthened to take this into account. There must be many thousands of buildings which have not been retrofitted.

 

Bangkok is less than 200 kilometres from Kanchanaburi, home to the Chedi Sam Ong fault line, and about 800km from Chiang Mai, where the Mae Ta and Mae Chan fault lines are located.

 

The Chedi Sam Ong, Mae Ta, and Mae Chan are among 13 active fault lines in Thailand covering 22 provinces.

http://www.bangkokpost.com/news/local/228664/2700-city-buildings-at-earthquake-risk

[macaroni21]

The last thing I wish to do is to sound alarmist, but we should not assume we know about all the faults that exist.

 

Wasn't the recent Christchurch earthquake due to a faultline that nobody even suspected was there? An article I read said that because the rock had been laid over with sedimentary deposits over time, there had been no sign that a fault ran through the deep rock until the ground moved. Christchurch also suffered badly because the alluvial soil liquefied; a common occurrence with this kind of soil in such events.

 

Nor are earthquakes always associated with mountainous regions or deep ocean trenches (like NZ, Aceh, California and Japan). The worst earthquake in the US east of the Rockies was that in New Madrid in 1812, estimated to have been 8.0 on the Richter scale. New Madrid was a settlement in Missouri on the Mississippi River. Once again, it was due to a fault deep under the flat alluvial plain.

[Guest voldemar]

The last thing I wish to do is to sound alarmist, but we should not assume we know about all the faults that exist.

 

Wasn't the recent Christchurch earthquake due to a faultline that nobody even suspected was there? An article I read said that because the rock had been laid over with sedimentary deposits over time, there had been no sign that a fault ran through the deep rock until the ground moved. Christchurch also suffered badly because the alluvial soil liquefied; a common occurrence with this kind of soil in such events.

 

Nor are earthquakes always associated with mountainous regions or deep ocean trenches (like NZ, Aceh, California and Japan). The worst earthquake in the US east of the Rockies was that in New Madrid in 1812, estimated to have been 8.0 on the Richter scale. New Madrid was a settlement in Missouri on the Mississippi River. Once again, it was due to a fault deep under the flat alluvial plain.

I agree. Unfortunately, we know very little about the nature of earthquakes. However, is not it true that Christchurch area had a history of Earthquakes?

[Guest fountainhall]

The whole of New Zealand sits on the seismically volatile 'ring of fire'. The main fault line seems to run from south west to north east, from the fiordland in the South Island up to the North Island where it splits into two. As such, it seems to pass to the west and north of Christchurch. According to wikipedia, there have been no earthquakes under or close Christchurch since records began in 1843. But there have been several not far to the north of the city.

 

What was so unfortunate about Christchurch is that the magnitude 6.3 was one of the smallest in the country's history. Yet, because it was relatively close to the surface (estimated now at 5 kms) and, as macaroni21 pointed out, the alluvial soil liquefied, it did immense damage. The recent Japan earthquake was much deeper at 32 kms, but about 8,000 times stronger.

 

As Bangkok is close to the sea and prone to sinking, I suspect the subsoil is not much different from that under Christchurch.