An earthquake in Bangkok is something people try not to think about. But the fact is any earthquake bigger than a 5.2 in or around Bangkok will likely send Bangkok’s skyline to the ground.
Anybody that has lived in Bangkok for more than a year or two will have seen countless construction projects with cranes sprouting out of the ground like weeds. It also does not take an engineering degree to see the construction framework is on the lean side as compared to other places in the world that have healthy building codes.
For example a column in a building in Bangkok may be a meter square for a building 10 or more stories tall. In California columns are 5 to 10 times as big for shorter buildings. The newer columns are round and not square to avoid fracturing at the corners.
Another factor to consider is the density of the cement used. Cement has a huge variety of mixes from light and porous to dense and very heavy. Many of the Bangkok buildings have the lighter cement as a cost saving measure.
Also Thai engineers have openly acknowledged the fact that the Bangkok buildings have no earthquake proofing. The alarm was raised shortly after the 9.0 December 2004 earthquake in Indonesia that shook buildings in Bangkok. There is no consideration for horizontal forces or cement fracturing.
Other factors that make Bangkok a disaster waiting to happen is Bangkok is sinking as a result of industrial water usage. The rate has been measured to be as much as 5cm per year. What that means is the earth under Bangkok is unstable and will tend to magnify the quake as the earth will likely liquify. The phenomenon was seen in San Francisco California in 1989 where some buildings were built on man made land that was once water. Almost all the buildings were destroyed in those areas. That was a 6.9 quake. So the damage of a 5.2 earthquake in Bangkok would likely result in damage of a 6.0 or higher.
In comparison to the 7.0 January 2010 earthquake in Haiti you must consider different factors for Bangkok. First off a 7.0 is a healthy earthquake in anyone’s book. With a 7.0 being 10 times more powerful than a 6.0 and 100 times more powerful than a 5.0, you quickly see a difference. However the buildings in Haiti are 2 to 4 stores tall in most cases and not 40 to 80 stores tall as in Bangkok. So some very crude math and practice with building houses made from playing cards and you can see the bigger they are the harder they fall.
Also the population difference must be considered. The population in the Bangkok metro area is about 12 million people. The entire population of Haiti is about 9 million with 2 million in Port-au-Prince. So if you multiply the death total in Haiti by a factor of 6 or 7, you would be near the potential death toll in Bangkok.
To say Bangkok will not suffer an earthquake is naive at best. There are 2 fault lines within about 25 miles of Bangkok. And both have been active further north. As the stress points along the fault shift with each earthquake, sooner or later there will be a significant earthquake in the Bangkok area.