Bangkok Buildings Face Amplified Earthquake Risk from Distant Tremors
We often think of risk in binary terms: safe or unsafe, likely or unlikely. But the reality, particularly when it comes to complex systems like urban infrastructure facing natural hazards, is far more nuanced. The recent Bangkok Post Knowledge Forum, featuring insights from Prof. Pennung Warnitchai of the Asian Institute of Technology (AIT), offered a stark reminder of this when discussing Bangkok’s vulnerability to earthquakes. As these recent findings reveal, Bangkok faces a unique seismic paradox: a relatively low probability of a direct, devastating earthquake, coupled with a high potential impact from tremors originating far away.
This paradox stems from a confluence of geographical and infrastructural factors. Bangkok isn’t situated directly on a major fault line, which leads to a sense of complacency. However, its geological makeup—soft soil atop a basin-like terrain—acts as an amplifier for seismic waves. Distant earthquakes, like the one originating in Myanmar’s Sagaing Fault earlier this year, can send tremors rippling across the region, amplified by the city’s geology, particularly affecting high-rise buildings.
This amplification effect creates a long-period ground motion, a slow, rolling sensation that can be particularly damaging to tall structures. Prof. Pennung highlighted that Bangkok’s soft soil can amplify ground motion by as much as four times, turning what might be a mild tremor elsewhere into a potentially dangerous event within the city.
The implications extend beyond mere inconvenience. While cosmetic damage is the most frequently reported outcome, the collapse of the State Audit Office (SAO) building in Chatuchak, even in its incomplete state, serves as a sobering reminder of the potential for catastrophic structural failure.
This situation calls for a layered approach to risk mitigation, addressing both the known vulnerabilities and the potential blind spots. While the Thai government, since 2007, has mandated earthquake-resistant building standards, a closer examination of enforcement and building integrity is necessary. Specifically, we must consider:
- Retrofitting older buildings: A significant portion of Bangkok’s building stock predates the 2007 regulations. The cost of retrofitting these structures can be prohibitive, but the long-term societal cost of inaction could be far greater.
- Material quality and corruption: The investigation into the SAO building collapse is crucial. If substandard materials or corruption played a role, it reveals a systemic vulnerability that must be addressed through stricter oversight and accountability.
- Zoning and building codes: While Bangkok is divided into ten zones with specific building codes based on risk levels, the effectiveness of these codes hinges on rigorous enforcement and continuous updating based on the latest seismic data.
- Public awareness: Equipping residents with knowledge of earthquake safety procedures and early warning systems can significantly reduce panic and improve response times in the event of a tremor.
The question then becomes: how do we reconcile the perception of low probability with the reality of potentially high-impact consequences? This is a question of risk management, of balancing cost and safety, and of fostering a culture of preparedness.
“Low probability is not the same as zero risk. The challenge lies in translating this understanding into proactive policies and investments that safeguard a city of millions against a threat that, while statistically unlikely, could have devastating consequences.”
Ultimately, Bangkok’s seismic vulnerability is not just a matter of geology or engineering. It is a matter of policy, governance, and public awareness. It requires a holistic approach that acknowledges the city’s unique vulnerabilities and proactively mitigates the risks. The future of Bangkok, in this regard, depends not just on the ground beneath its feet, but also on the choices made above it.
