Professor Warns Bangkok Quake Risk From Soft-Soil Basin

Bangkok’s underlying soft-soil basin could significantly amplify earthquake shaking by three to six times and prolong tremors for up to two minutes, according to Prof Dr Pennung Warnitchai, director of the Earthquake Research Centre of Thailand. The findings suggest the capital may be more vulnerable to seismic activity than previously assumed, particularly affecting tall buildings.

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Recent earthquakes have been linked to movement along Myanmar’s Sagaing Fault, involving slip in its mid-section. However, Pennung warned that if movement occurs in a deeper segment closer to Thailand, the potential impact on Bangkok could be far more severe.

He explained that the city’s geology is the primary risk factor rather than its distance from seismic sources. Data from vibration monitoring stations show that peak ground acceleration outside the soft-soil basin may reach only 3-6 mg (milli-g, the unit used in seismology to describe acceleration), but can increase to around 20 mg once seismic waves enter the basin.

The shaking pattern in Bangkok is also distinct, with slower oscillations lasting longer than typical earthquakes. These waves tend to amplify specific frequencies of around 1.6 seconds, 2.8 seconds, and 6.3 seconds per cycle, closely matching the natural sway periods of many high-rise buildings.

Pennung highlighted resonance as a key factor in structural damage. Surveys found that around 10 percent of nearly 1,000 mid-rise buildings of about 24 storeys, with a sway period of 2.4 seconds, showed damage. In contrast, three out of six very tall buildings of around 60 storeys, with a sway period of about six seconds, were damaged, representing roughly 50 percent.

Damage ranged from minor non-structural cracking to severe structural deformation, and was observed across multiple districts with dense clusters of high-rise buildings.

To reduce risks, Pennung urged wider installation of dampers, which can increase a building’s energy dissipation from 1-2.5 percent to 5-10 percent. He noted that similar approaches are widely used in Japan to improve structural resilience.

He also proposed a 60-second earthquake early warning system based on fast-moving P-waves, which arrive before the more destructive S-waves. Measurements at the Queen Sirikit National Convention Centre indicate Bangkok could receive about one minute of advance warning. Such a system would allow critical infrastructure to be shut down and people to take protective action before strong shaking begins.

The Nation reported that the centre plans to install structural health monitoring equipment in at least 20 pilot buildings in Bangkok, Chiang Mai and Chiang Rai next year, aiming to improve safety standards and align Thailand’s infrastructure with international practices.

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Adapted by ASEAN Now Nation 3 Apr 2026