2:45 PM - 3:00 PM
[O12-05] Seismic response of high-rise buildings and long-period ground motion in the Bangkok Metropolitan Area, Thailand, during the 2025 Myanmar earthquake
★Invited Papers
Keywords:the 2025 Myanmar earthquake, Bangkok, high-rise building, long-period ground motion, deep sedimentary layers, surface wave
In the 2025 Myanmar earthquake, many high-rise buildings in the Bangkok Metropolitan area of Thailand were shaken, and some were damaged observed even though the area is located at the epicentral distance more than 1,000 km. In particular, a building under construction collapsed resulting in casualties. Furthermore, water overflowed from pools on the roofs of the high-rise buildings. Videos of these high-rise buildings during the earthquake have been posted on YouTube and other internet sites. Since there have been no large historical earthquakes in Bangkok, the damage caused to the high-rise buildings by this event has become a major public concern. It is known that this area has thick deep sediments, which can amplify long-period ground motions with periods more than 1 second (Poovarodom and Jirasakjamroonsri, 2015; Subedi et al., 2021; Ornthammarath et al., 2023). It is highly expected that the amplification of long-period ground motions by the deep sediments can affect the large seismic response of the high-rise buildings. In this study, we estimated the behavior of high-rise buildings during the earthquake by analyzing videos and microtremor observations to examine the relationship between the seismic response of the high-rise buildings and the long-period motions.
To analyze the behavior of the high-rise buildings in the area, we collected videos on YouTube. We found videos of 34 high-rise buildings with a basis on the criteria that the entire building was included in the videos and that the natural period could be identified by water overflow from the buildings. The obtained videos were analyzed using two methods by Andaya et al. (2022). These methods are to estimate the natural period from images of water overflowing from a pool on the roof of the building and to estimate the building displacement waveform by pixel tracking of video images. The natural periods of 26 buildings were obtained by the water overflow video analysis. In the pixel tracking analysis, displacement waveforms were estimated for five buildings, and the natural periods were obtained from their spectra. Furthermore, the natural periods of three of these four buildings were also obtained from the water overflow analysis. Most of the buildings that experienced the water overflow were 100 to 150 m tall, and have natural periods of 3 to 5 seconds. The tallest high-rise building examined was about 300 m tall, with a natural period of about 6.5 seconds. In some of these high-rise buildings, damage to non-structural components was observed, such as the falling of glass fences from the rooftop pools and damage to walkways connecting multiple buildings. We were currently unable to analyze the behavior of the collapsed building mentioned above.
In early May 2025, microtremor observations were conducted at the high-rise buildings mentioned above. Single-point microtremor observations using a high-sensitivity velocity sensor were conducted on the ground surface near 13 buildings. A VSE-15L1 was used to ensure sufficient observation of long-period microtremors. Microtremor observations were also conducted on the rooftops (four locations) and basements (one location) of five buildings. For microtremor observations on the buildings, four sets of JU410 were used on the rooftop, and a JEP6A3 was used in the basement. In the horizontal-vertical spectral ratios of the microtremor observation data on the surface, peaks were observed at periods of around 7-10 seconds and 2-3 seconds at many locations. This characteristic has been pointed out in the previous studies, and it was found that the deep sedimentary layers’ characteristics greatly amplify long-period seismic motion. Strong motion records from this earthquake were also obtained in the Bangkok Metropolitan area, and long-period surface waves at periods of 6-8 seconds were prominent (Maruyama, 2025). The surface waves were amplified by the deep sedimentary layers in the Bangkok area, and this can be the cause of the strong shaking of the high-rise buildings.
In the 2025 Myanmar earthquake, the long-period ground motion was predominant in the Bangkok Metropolitan area, far from the epicenter, and high-rise buildings shook strongly. Such shaking of high-rise buildings due to relatively distant earthquakes has also been observed in Singapore (Megawati et al., 2003) and Metro Manila (Andaya et al., 2022) during the past events. It therefore is a common problem for high-rise buildings in megacities in Asia. In the future, it is expected that seismologists and earthquake engineers work together to evaluate long-period ground motion and consider measures to prevent damage to large-scale structures.
To analyze the behavior of the high-rise buildings in the area, we collected videos on YouTube. We found videos of 34 high-rise buildings with a basis on the criteria that the entire building was included in the videos and that the natural period could be identified by water overflow from the buildings. The obtained videos were analyzed using two methods by Andaya et al. (2022). These methods are to estimate the natural period from images of water overflowing from a pool on the roof of the building and to estimate the building displacement waveform by pixel tracking of video images. The natural periods of 26 buildings were obtained by the water overflow video analysis. In the pixel tracking analysis, displacement waveforms were estimated for five buildings, and the natural periods were obtained from their spectra. Furthermore, the natural periods of three of these four buildings were also obtained from the water overflow analysis. Most of the buildings that experienced the water overflow were 100 to 150 m tall, and have natural periods of 3 to 5 seconds. The tallest high-rise building examined was about 300 m tall, with a natural period of about 6.5 seconds. In some of these high-rise buildings, damage to non-structural components was observed, such as the falling of glass fences from the rooftop pools and damage to walkways connecting multiple buildings. We were currently unable to analyze the behavior of the collapsed building mentioned above.
In early May 2025, microtremor observations were conducted at the high-rise buildings mentioned above. Single-point microtremor observations using a high-sensitivity velocity sensor were conducted on the ground surface near 13 buildings. A VSE-15L1 was used to ensure sufficient observation of long-period microtremors. Microtremor observations were also conducted on the rooftops (four locations) and basements (one location) of five buildings. For microtremor observations on the buildings, four sets of JU410 were used on the rooftop, and a JEP6A3 was used in the basement. In the horizontal-vertical spectral ratios of the microtremor observation data on the surface, peaks were observed at periods of around 7-10 seconds and 2-3 seconds at many locations. This characteristic has been pointed out in the previous studies, and it was found that the deep sedimentary layers’ characteristics greatly amplify long-period seismic motion. Strong motion records from this earthquake were also obtained in the Bangkok Metropolitan area, and long-period surface waves at periods of 6-8 seconds were prominent (Maruyama, 2025). The surface waves were amplified by the deep sedimentary layers in the Bangkok area, and this can be the cause of the strong shaking of the high-rise buildings.
In the 2025 Myanmar earthquake, the long-period ground motion was predominant in the Bangkok Metropolitan area, far from the epicenter, and high-rise buildings shook strongly. Such shaking of high-rise buildings due to relatively distant earthquakes has also been observed in Singapore (Megawati et al., 2003) and Metro Manila (Andaya et al., 2022) during the past events. It therefore is a common problem for high-rise buildings in megacities in Asia. In the future, it is expected that seismologists and earthquake engineers work together to evaluate long-period ground motion and consider measures to prevent damage to large-scale structures.