Quaking with anticipation
How worried should Bangkokians be about a major earthquake?
The question of whether Bangkok’s infrastructure is prepared for an earthquake arises whenever we hear news about it happening elsewhere the world. Earthquake-prone New Zealand suffered two months back, and Japan has them often, big and small. Should Bangkok, situated in a safer part of the Earth’s untrustworthy crust and yet with more and more tall buildings, be complacent?
At a seminar held last month titled “Design Of Tall Buildings: Trends And Advancements For Structural Performances”, Pennung Warnitchai, a leading scholar on earthquakes, offered his view on the subject. Pennung is a professor in structural engineering, disaster preparedness, mitigation and management, and his advice is that we shouldn’t be complacent.
“It is difficult say how vulnerable the city is to earthquakes. What I can share with you is the ground motion expected in the event of an earthquake in the capital, which according to our research should not be that strong. But although it is not expected to be so strong, it is possible to shake some types of buildings to the level that they can be seriously damaged. Some of them may even collapse.
“We have seen that in some countries the ground motion might not be that strong, but it’s the long-period ground motion that can create a resonant response, which in turn can cause the shaking of tall buildings.
“The problem now is that we have a large number of tall buildings in Bangkok, and some of them are weak and some strong.”
Statistics from the Seismological Bureau, Thai Meteorological Department, reveal that tiny earthquakes happen in Thailand nearly every day, though most of them are too small for us to even feel. For instance, a week into 2017 there have already been nearly 50 registered quakes, with only one of them — in Tak province, at 3.9 on the Richter scale — felt by civilians. In December 2016, there were three quakes in the North with reports of people feeling the shakes.
Bangkok, however, seems safer. There are many levels of earthquakes that could also occur in Bangkok, Pennung continued. The one that most people residing or working in high-rises can experience every three or four years is not a strong one. People living in low-rise buildings, under 15 floors, generally don’t experience these.
“The worrisome earthquakes are the ones 10 to 20 times larger than that. And, yes, it is possible that we can experience them in Bangkok. The earthquake that can
create this type of impact will most likely originate about 6-8km from Bangkok. We have geological evidence that a large earthquake happened about 300 years ago in that particular area, and that it could happen again,” said the researcher.
“We have determined the location to be around the boundary between two tectonic plates, from the western side of Myanmar down to the Andaman Islands. If indeed a large earthquake happens there, it will have a big impact on tall buildings in Bangkok. There is no predicting when this will happen.
“Another possibility is an earthquake of a magnitude 7 in Kanchanaburi province. This is a different type of earthquake,
created by a fault line in the province. This fault line, which we call cluster fall, is a shallow fall, so it is not able to create a magnitude 8 or 9 quake. It creates a smaller-magnitude earthquake, maximum 7-7.5, but the distance to Bangkok is about 200km, so it’s close.”
Pennung and his team are working closely with the Bangkok Metropolitan Administration to set up a building-certification system, to ensure better implementation of safety measures by building developers, to help infrastructure in the capital withstand earthquakes and natural hazards.
Meanwhile, to get a better idea of what buyers of high-rise condominiums should be asking their developers, we spoke with Dr Naveed Anwar, executive director and CEO of AIT Solutions, whose expertise encompasses the modelling and analysis of bridges, tall buildings and special structures.
Consumers, he said, need to ask developers questions such as what standards have been used for the designs of the buildings to withstand natural hazards and of course earthquakes. The common reply will be that they have followed the building code, upon which they should ask whether they have implemented standards higher than that.
Moreover, developers also need to be asked if they have done Performance Based Design (PBD), a new method of design which guarantees that they have gone beyond the basic building-code standard. In fact, continued the researcher, consumers may pay more for developers using PBD, but in the long run they will benefit from it. It is not just about keeping the building safe, with minimal damage in the event of natural disasters and earthquakes, but also addressing wear and tear.
Anwar said other inquires to be made include those about the design of the building, what’s been done to improve its durability, and approaches taken to make it a green building.
“A majority of buyers don’t know much when it comes to asking developers if they are getting better safety for the price they’re paying,” he said. “This is something buyers often overlook because they cannot see [the structure] with the naked eye. While they can see furniture and amenities, structure is not something they can view openly.
“Once, I heard a developer saying they never negotiate with the architect for his fee but always with the engineer, because an architect’s work is visible and an engineer’s work isn’t.”
Anwar concluded by telling about earthquake-prone New Zealand, reported to have one of the best design codes for earthquakes.
“When they had an earthquake in Christchurch a couple years ago, there were few fatalities, but the whole central business district was shut down for two-and-a-half years for repairs. They calculated the loss to be around 180 billion baht.
“So my point here is that having earthquake-resistant buildings is not just about lowering the number of casualties, but the money and time that are lost. So it is not just the death toll but the livelihood of the people that we have to keep in mind when purchasing property.”
It is possible that we can experience worrisome earthquakes in Bangkok. The earthquake that can create this type of impact will most likely originate about 6-8km from Bangkok. We have geological evidence that a large earthquake happened about 300 years ago in that particular area, and that it could happen again