The earthquake that struck Myanmar on March 28 sent tremors through many high-rise buildings in Bangkok, shaking not just the structures but also buyer confidence, if only briefly.
While many question the safety of living in vertical structures, homebuyers have become more cautious, scrutinising each project's safety standards, contractor reputation and long-term reliability more closely.
WHY DID THE MYANMAR EARTHQUAKE SHAKE BUILDINGS MORE THAN 1,300 KILOMETRES AWAY IN BANGKOK?
Prof Pennung Warnitchai, chair of the structural engineering programme at the Asian Institute of Technology, said the tremors were caused by Bangkok's deep, soft soil basin, which extends as far as 800 metres below the surface.
"Bangkok lies at the bottom of a soft-soil basin, much like the bottom of a frying pan," he said. "The rim of this geological pan stretches to Chachoengsao, Nakhon Nayok and Ayutthaya, forming a unique bowl of soft soil."
This type of soil can significantly amplify long-period, low-frequency seismic waves from distant earthquakes by as much as 3-4 times, as they pass through the basin, said Prof Pennung.
When such waves hit Bangkok, they can trigger a resonance effect in high-rise buildings, particularly those that have a natural sway frequency aligned with that of the seismic waves.
For example, 50-storey buildings typically have a natural vibration period of about 5 seconds, while buildings with 20 to 40 storeys range from 2-4 seconds, matching the wave period and intensifying the swaying motion.
These buildings are especially affected, which aligns with real-life observations, such as water sloshing in rooftop pools, and in rare cases, structural failures like the collapse of the State Audit Office building, he said.
BASED ON THE DAMAGE FROM THE RECENT EARTHQUAKE, SHOULD THE PUBLIC BE CONCERNED?
Prof Pennung, who also serves as director of the National Earthquake Research Center of Thailand, said the recent quake damaged hundreds of buildings in Bangkok, though mostly non-structural parts such as walls, ceilings, glass panels, elevators and utility systems.
"These damages show that buildings in Thailand can generally withstand seismic vibrations, but non-structural impacts may render many buildings temporarily unusable or uninhabitable," he said.
Only around a dozen buildings suffered structural damage, with one building collapsing, which should not have occurred if the structure was designed in full compliance with existing laws, said Prof Pennung.
Asst Prof Thanes Weerasiri, president of the Council of Engineers Thailand, said high-rise buildings are designed to sway without breaking, much like a flexible plastic ruler, thanks to their elastic design.
"All buildings taller than 23 metres constructed after 2007 comply with seismic design codes," he said. "Cracks in non-structural walls are common. As long as beams and floors remain intact, the structure is safe."
In addition, all high-rise and large-scale buildings in Bangkok are subject to annual safety inspections, with a more comprehensive structural inspection required every five years, said Asst Prof Thanes.
Under the Building Control Act of 2000, nine types of buildings must undergo mandatory inspections due to their size or usage.
These include high-rise buildings greater than 23 m in height and large-scale buildings with more than 10,000 square metres of usable area. Assembly buildings must be inspected if they have more than 1,000 sq m of space or host more than 500 people.
Other buildings include theatres, hotels with more than 80 rooms, condos larger than 2,000 sq m, multi-storey factories exceeding 5,000 sq m, and entertainment venues with more than 200 sq m of space.
Signs are mandated for buildings greater than 15 m in height, larger than 50 sq m, or for rooftops larger than 25 sq m.
"Following the earthquake, buildings should be re-analysed. We are working to build public confidence and prepare for future seismic risks, including the fault line in Kanchanaburi," he said.
"The public should trust the engineers conducting these inspections, as buildings cleared by engineers are safe to occupy."
HOW HAS THE EARTHQUAKE AFFECTED HOMEBUYER SENTIMENT?
Property research firm Terra Media and Consulting Co conducted a survey on homebuyer behaviour and confidence following the earthquake in March.
The survey was conducted between April 28 and May 19, and had 600 respondents, mostly in Greater Bangkok, across various age and income brackets.
The study found condo residents were more affected than those in low-rise houses. Among respondents, 68% reported non-structural damage such as cracked walls, while only 5% experienced critical damage involving building structures or utility systems.
"After the incident, only 4% of respondents decided to relocate," said Sumitra Wongpakdee, managing director of Terra. "For those who moved, their housing preferences changed after the quake."
The survey indicated 67% of respondents felt less comfortable and unhappy with their homes, 52% shifted their preference from condos to low-rise homes, and 42% increased their budget for a property they deemed structurally safer and more service-reliable.
"Roughly 95% said they would switch brands and look for a trustworthy developer. They prioritised companies with proven safety standards, reliable contractors and a strong sense of accountability," said Ms Sumitra.
Following the earthquake, the key factors for home choice shifted. Buyers now want fair pricing and good quality, especially in the mid-range segment, from reputable brands, according to Terra. Luxury and aesthetic factors were less influential.
Terra's comparison of top brand attributes from 2024 and 2025 revealed a clear shift. In 2024, consumers valued quality most, but after the quake, construction standards and corporate responsibility became the top brand selection criteria, which should be a wake-up call to developers, she said.
"Some respondents asked: 'What's the difference between quality and standards?'" said Ms Sumitra. "From the buyer's point of view, standards mean knowing the developer uses trusted construction firms that make them feel safe."
COULD BANGKOK FACE A SIMILAR EARTHQUAKE, AND HOW SHOULD PEOPLE PREPARE?
Prof Pennung said Greater Bangkok is at risk from distant earthquakes. The region can be affected by tremors originating in Myanmar, the Andaman Sea and northern Thailand -- areas known for frequent seismic activity.
"Although Bangkok has no active fault lines directly beneath it, it still feels tremors from distant seismic events due to the proximity to the Sagaing Fault, one of the world's top three most dangerous faults, capable of producing magnitude 7 earthquakes," he said.
Recognising this risk, Thailand introduced seismic building codes in 2007. Bangkok and four surrounding provinces were declared regulated zones due to their soft-soil basin, with more provinces added later. These codes also set professional standards for engineers.
According to the Department of Public Works and Town & Country Planning, a 2018 update divided Bangkok's basin into 10 seismic zones.
Each zone has graphs showing expected shaking levels by building period, guiding structural engineers in their design calculations.
"Thailand's real estate sector has significantly advanced in seismic design standards. Stricter building codes, especially the 2021 regulation, marked major progress by requiring new buildings to meet higher safety and resilience standards across more building types," said Prof Pennung.
He said new developments must follow precise requirements under the 2021 ministry regulation, which governs structural load, resistance, durability and soil support. These guidelines ensure buildings can better withstand earthquake forces.
Most major developers are adhering to these standards, incorporating advanced engineering techniques and up-to-date seismic technologies in new construction, reflecting growing industry-wide awareness and responsibility, said Prof Pennung.
"The chance of a repeat event of the March 28 quake is low, perhaps less than 10% in a person's lifetime. But as engineers, we must always be prepared," he said.
WHAT LESSONS HAVE EXPERTS LEARNED FROM THIS EARTHQUAKE?
Despite strict building codes, proper design and construction practices are crucial to ensure earthquake resistance, said Prof Pennung. Compliance with legal standards alone is not enough -- execution must also be sound.
He said a key issue is the damping ratio -- the rate at which a building dissipates energy during shaking. While it was once assumed to be 5% for tall buildings, global and local data now suggest Bangkok's high-rises may have damping ratios closer to 1-2.5%.
"Lower damping ratios mean buildings sway more than previously predicted. To mitigate this, Thailand should adopt advanced technologies already used in earthquake-prone countries such as Japan," said Prof Pennung.
These innovations include energy-dissipation devices such as viscous dampers or oil dampers, which absorb seismic energy and reduce the building's overall movement during an earthquake.
"Public awareness also plays a vital role," he said. "Educating citizens about earthquake risks and preparedness is important, while efficient emergency response plans can minimise damage and ensure safety when disaster strikes."
