This study investigates the amplification of ground motion in Bangkok, Thailand, due to distant earthquakes. Researchers analyzed seismic data from five recent earthquakes, focusing on the deep sedimentary basin underlying the city. Results confirm significant ground motion amplification, particularly at longer periods (0.5-2 seconds), which correspond to the natural frequencies of tall buildings. The amplification patterns vary spatially across Bangkok, with higher amplification observed in the central and western areas characterized by thicker, softer sediments. These findings highlight the seismic vulnerability of Bangkok's high-rise structures and underscore the need for incorporating site-specific ground motion amplification factors in seismic design and risk assessments.
Scientists studying seismic waves traveling through the Earth's core have found evidence suggesting the inner core's growth isn't uniform. Analysis indicates the eastern hemisphere of the inner core under Indonesia's Banda Sea is growing faster than the western hemisphere under Brazil. This asymmetrical growth may be influencing the Earth's magnetic field, as the inner core's crystallization releases heat that drives the churning motion of the outer core, responsible for generating the field. While the exact mechanisms and implications remain uncertain, this research offers new insights into the complex dynamics deep within our planet.
HN commenters discuss the study's methodology and implications. Several express skepticism about the ability to accurately measure such deep Earth phenomena, questioning the certainty of the "paused" or reversed rotation claims. Some suggest alternative explanations for the observed data, like changes in the mantle's electromagnetic field influencing measurements. Others find the research fascinating, speculating about potential effects on Earth's magnetic field and the length of a day, albeit minor ones. A few highlight the limitations of current understanding of the Earth's interior and the need for further research. The overall tone is one of cautious interest mixed with scientific scrutiny.
Summary of Comments ( 0 )
https://news.ycombinator.com/item?id=43512206
HN commenters discuss the challenges of building in Bangkok due to its soft soil, which amplifies seismic waves and increases the risk of liquefaction. Some express skepticism about the study's focus on distant earthquakes, arguing that local faults pose a more immediate threat, though less frequent. Others point out the difficulty in predicting ground motion accurately due to the complex interplay of factors, including soil type, depth to bedrock, and the frequency of the seismic waves. Several commenters raise concerns about the lack of preparedness and building codes in Bangkok, suggesting the city's vulnerability is underestimated. One commenter with experience in geotechnical engineering emphasizes the importance of proper soil investigation and foundation design to mitigate risks. Overall, the comments highlight the significant earthquake risk Bangkok faces and the need for better preparedness.
The Hacker News post linking to the Springer Open article "Analysis of amplified ground motion in Bangkok from recent earthquakes (2023)" has a modest number of comments, focusing primarily on the geological and geotechnical context of Bangkok and its implications for earthquake risk.
One commenter points out the soft soil profile of Bangkok, built on a former delta, which makes it particularly vulnerable to ground motion amplification. They explain that seismic waves slow down in soft soil, leading to increased shaking intensity. This commenter also mentions the Mexico City earthquake of 1985 as a comparable example of significant damage in a city built on a former lakebed. They emphasize the importance of soil type in determining earthquake risk.
Another commenter highlights the challenge of retrofitting existing buildings in Bangkok to mitigate this risk, given the high density and existing infrastructure. They speculate that the potential cost and disruption associated with such a large-scale undertaking might be a deterrent to action.
A further comment builds upon the discussion of Bangkok's geology by mentioning that parts of the city are essentially floating on a layer of clay. They characterize the situation as precarious and highlight the amplified risk due to this unique geological feature. This commenter also draws a parallel with other cities built on soft ground.
One commenter offers a more technical perspective by mentioning the "site effects" discussed in the paper. They suggest looking into microzonation studies of Bangkok for more detailed information on localized variations in ground motion amplification.
The discussion also briefly touches upon the relatively low seismic activity in the region historically, which might contribute to a lower level of awareness and preparedness compared to areas with more frequent earthquakes. One commenter expresses surprise about the perceived low earthquake risk in Bangkok, given the information presented in the linked study.
In general, the comments on Hacker News reflect a concern about the earthquake risk faced by Bangkok due to its specific geological and geotechnical characteristics. The commenters underscore the significance of ground motion amplification in soft soils and the challenges associated with mitigating this risk in a densely populated city. While the number of comments is not extensive, they offer valuable insights and further context to the linked scientific study.