Seismic site characteristics of shallow sediments in the Bangkok Metropolitan Region, and their inherent relations

• Published in: Bulletin of engineering geology and the environment 2019-04, Vol.78 (3), p.1327-1343
• Main Authors: Jirasakjamroonsri, Amorntep, Poovarodom, Nakhorn, Warnitchai, Pennung
• Format: Article
• Language: English
• Subjects: Autocorrelation; Clay; Correlation analysis; Data processing; Earth and Environmental Science; Earth Sciences; Foundations; Geoecology/Natural Processes; Geoengineering; Geological engineering; Geotechnical Engineering & Applied Earth Sciences; Hydraulics; Methods; Metropolitan areas; Nature Conservation; Original Paper; Phase velocity; Profiles; Regression analysis; Sediments; Seismic velocities; Shear wave velocities; Soft clay; Spatial distribution; Spatial variations; Velocity; Wave velocity; Wavelengths
• ISSN: 1435-9529; 1435-9537
• DOI: 10.1007/s10064-017-1220-3

This paper presents the site characteristics of soft deposits in Bangkok Metropolitan Region, and their inherent relations, which were explored using microtremor observations. The predominant period ( T P ) and shear wave velocity ( V S ) profiles from the surface to a 100-m depth at 150 sites over an area of approximately 150 × 200 km were explored using the Horizontal-to-Vertical (H/V) spectral ratio method and the Spatial Autocorrelation (SPAC) method, respectively. Spatial variations of T P and average V S are presented in maps and discussed with the distribution of soft clay. The results show that the shallow structure is rather uniform in the central area, having low V S , long T P , and thick soft clay. V S increases, while T P tends to decrease gradually towards the north and east and more sharply towards the west. Using a number of the observed site characteristics, relations among the average V S at different depths and T P were examined. Regression analysis revealed high correlations and almost linear relations among them, suggesting that V S at deep strata could be simply estimated from the shallow V S or T P . Finally, a simple scheme to estimate the V S profile using only the phase velocity at specific wavelengths is proposed.