Seismic amplification and resonance effects of the 2025 Myanmar earthquake in Bangkok’s soft-soil area

Graduate School, Universitas Andalas, Padang, Indonesia

^* Corresponding author: bistijono@eng.unand.ac.id

Abstract

The 7.7 Mw earthquake that struck the Sagaing region, Myanmar, on March 28, 2025, caused cross-border seismic effects felt as far as Bangkok, Thailand, about 600 km from the epicenter. Although considered a low-seismic-risk area, tremors of intensity IV–V on the Modified Mercalli (MMI) scale produced strong shaking in high-rise buildings and led to the collapse of construction projects in the Chatuchak District. This study examines the relationship between Bangkok’s geotechnical conditions and the dynamic responses of buildings to the 2025 Myanmar earthquake. The qualitative-descriptive method includes literature review, field observations in Sathorn, Silom, and Chatuchak, and comparative analysis with the 2011 Tohoku and 2015 Nepal earthquakes. Results indicate that a 15–30 m thick water-saturated clay layer with a shear wave velocity (Vs30) below 150 m/s and a dominant period of 1.8–2.5 seconds amplified ground motion up to twice the theoretical value. This condition triggered ground–structure resonance, affecting buildings with 15– 25 storeys and deep-pile foundations, as well as flexible structures. The Chatuchak collapse was due to resonance combined with poor construction stability. These findings confirm that long-period waves pose significant risks to delta cities, such as Bangkok, underscoring the need to revise national seismic design standards by incorporating local amplification and long-period effects in soft soil zones.