BANGKOK, THAILAND – Thai earthquake researcher Prof. Dr. Pennung Warnitchai warned that Bangkok’s soft ground basin could strongly amplify seismic waves and prolong shaking for up to two minutes, putting high‑rise buildings at particular risk and calling for more dampers and a 60‑second early warning system.
Why Bangkok might face higher earthquake risk than assumed
According to Prof. Dr. Pennung Warnitchai, director of the Earthquake Research Centre of Thailand, the underground conditions in Bangkok could significantly amplify earthquake vibrations and make them last longer. He said that the danger to buildings depended not only on the distance to the epicentre but also on the local geology of the capital, which could increase structural loads.
“It is not only the distance to the epicentre that matters, but above all the local geology of Bangkok, which can increase the stress on buildings.”
said Prof. Dr. Pennung Warnitchai, director of the Earthquake Research Centre of Thailand.
Link to Myanmar’s Sagaing Fault
Warnitchai explained that recent earthquakes had been associated with movement along the Sagaing Fault in Myanmar, particularly with slip in the central segment of the fault. He noted that a different pattern of movement could pose greater danger to Thailand.
“If slip occurs in a deeper segment of the Sagaing Fault closer to Thailand, the impact on Bangkok could be significantly more severe.”
said Prof. Dr. Pennung Warnitchai, director of the Earthquake Research Centre of Thailand.
The “soft basin” as an amplifier for seismic waves
Measurement data from vibration monitoring stations showed, according to Warnitchai, that outside the soft ground basin the maximum ground acceleration of incoming waves was in some cases only 3–6 mg. Once these waves entered the Bangkok basin, however, they could be amplified to around 20 mg, roughly three to six times stronger.
“Our measurements indicate that when seismic waves enter the Bangkok basin, ground acceleration can increase to around 20 mg – about three to six times higher than outside the soft basin.”
said Prof. Dr. Pennung Warnitchai, director of the Earthquake Research Centre of Thailand.
Long, slow shaking: up to two minutes of tremors
Another characteristic identified for Bangkok was a special vibration pattern with relatively slow but longer‑lasting shaking that could continue for up to two minutes. Warnitchai said certain frequencies were particularly amplified, including cycles of around 1.6, 2.8 and 6.3 seconds.
These frequencies could become critical when they coincided with the natural periods of buildings, increasing the risk of damage. He stressed that this interaction had to be taken into account in design and assessment.
“Bangkok can experience slow but long-lasting shaking of up to two minutes, and specific frequency bands are especially amplified, which becomes a problem when they match the natural periods of buildings.”
said Prof. Dr. Pennung Warnitchai, director of the Earthquake Research Centre of Thailand.
Resonance effect: why some towers suffer more damage
Warnitchai pointed to resonance as a key explanation for why neighbouring structures might be affected very differently during the same event. If the natural vibration period of a building matched the amplified earthquake frequency, damage could increase sharply.
Damage assessments showed that high‑rise buildings of around 24 storeys with a vibration period of about 2.4 seconds had suffered damage in roughly 10% of almost 1,000 buildings examined. These structures were particularly exposed when their natural period fell into one of the amplified frequency ranges.
“Our assessments show that around 10% of almost 1,000 high-rises of about 24 storeys exhibited damage when their natural period matched the amplified frequencies.”
said Prof. Dr. Pennung Warnitchai, director of the Earthquake Research Centre of Thailand.
Very tall buildings most exposed: half of inspected towers damaged
The proportion was significantly higher for very tall buildings of around 60 storeys, with a vibration period of roughly 6 seconds. Among six such buildings studied, three showed damage, corresponding to about 50% of this group.
According to Warnitchai, the damage ranged from “green” (non‑load‑bearing cracks) to “red” (severe structural damage with deformed reinforcement). The affected towers were located in several high‑rise clusters rather than in a single confined area.
“Among very tall buildings of around 60 storeys, three out of six inspected towers—about 50%—showed damage, from green to red levels, and these cases were spread across several high-rise clusters.”
said Prof. Dr. Pennung Warnitchai, director of the Earthquake Research Centre of Thailand.
Technical countermeasures: more dampers like in Japan
As a central engineering solution, Warnitchai highlighted the installation of dampers, or vibration absorbers, which reduce oscillations and dissipate energy. Many tall buildings in Thailand currently had only low damping levels of about 1–2.5%, he said.
With dampers, this could be increased to 5–10%, significantly improving performance and reducing seismic impact. Warnitchai compared this approach to practices in Japan, where such technology had been widely implemented.
“Many tall buildings in Thailand currently have damping of only about 1–2.5%; with dampers we can raise this to 5–10%, which clearly improves their performance, similar to what we see in Japan.”
said Prof. Dr. Pennung Warnitchai, director of the Earthquake Research Centre of Thailand.
Early warning with P-waves: around 60 seconds gained
Warnitchai also emphasised an earthquake early warning system that would use fast P‑waves, which arrived before the more destructive S‑waves. Measurements at the Queen Sirikit National Convention Centre suggested that Bangkok could have roughly one minute of warning time.
This interval could be sufficient to shut down critical systems or initiate protective actions in sensitive facilities and high‑rise buildings. Warnitchai argued that such a warning window would provide a meaningful safety benefit for the city.
“Our measurements at the Queen Sirikit National Convention Centre indicate that Bangkok could gain about 60 seconds of warning time—enough to stop critical systems or trigger protective measures.”
said Prof. Dr. Pennung Warnitchai, director of the Earthquake Research Centre of Thailand.
Planned monitoring of buildings in Bangkok and northern Thailand
The research centre planned to install measurement and monitoring technology for structural condition control in at least 20 pilot buildings over the coming year. According to Warnitchai, the sites would be located in Bangkok, Chiang Mai and Chiang Rai.
These systems were intended to enhance safety and bring Thailand’s infrastructure closer to international standards. Continuous monitoring would also help engineers better understand how different structures responded to earthquakes.
“We plan to equip at least 20 pilot buildings in Bangkok, Chiang Mai and Chiang Rai with monitoring systems next year, so we can improve safety and move Thailand’s infrastructure closer to international standards.”
said Prof. Dr. Pennung Warnitchai, director of the Earthquake Research Centre of Thailand.