Seismic microzonation of the greater Bangkok area using microtremor observations

Tuladhar, Rabin, Yamazaki, Fumio, Warnitchai, Pennung, and Saita, Jun (2004) Seismic microzonation of the greater Bangkok area using microtremor observations. Earthquake Engineering and Structural Dynamics, 33 (2). pp. 211-255.

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Bangkok, the capital city of Thailand, is located at a remote distance from seismic sources. However, it has a substantial risk from these distant earthquakes due to the ability of the underlying soft clay to amplify ground motions. It is therefore imperative to conduct a detailed seismic hazard assessment of the area. Seismic microzonation of big cities, like Bangkok, provides a basis for site-specific hazard analysis, which can assist in systematic earthquake mitigation programs. In this study, a seismic microzonation map for the greater Bangkok area is constructed using microtremor observations. Microtremor observations were carried out at more than 150 sites in the greater Bangkok area. The predominant periods of the ground were determined from the horizontal-to-vertical (H/V) spectral ratio technique. A microzonation map was then developed for the greater Bangkok area based on the observations. Moreover, the transfer functions were calculated for the soil profile at eight sites, using the computer program SHAKE91, to validate the results from the microtremor analysis. The areas near the Gulf of Thailand, underlaid by a thick soft clay layer, were found to have long natural periods ranging from 0.8s to 1.2s. However, the areas outside the lower central plain have shorter predominant periods of less than 0.4s. The study shows that there is a great possibility of long-period ground vibration in Bangkok, especially in the areas near the Gulf of Thailand. This may have severe effects on long-period structures, such as high-rise buildings and long-span bridges.

Item ID: 16826
Item Type: Article (Research - C1)
ISSN: 1096-9845
Keywords: microzonation; Bangkok; microtremors; predominant period; H/V spectral ratio
Date Deposited: 28 Jul 2011 02:36
FoR Codes: 09 ENGINEERING > 0905 Civil Engineering > 090504 Earthquake Engineering @ 50%
09 ENGINEERING > 0905 Civil Engineering > 090506 Structural Engineering @ 50%
SEO Codes: 87 CONSTRUCTION > 8702 Construction Design > 870201 Civil Construction Design @ 100%
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