Seismic microzonation and hazard assessment of Ha Noi based on microtremor observations
- Bangkok : Asian Institute of Technology, 2003
- 58 leaves : ill.
- Thesis ; no. ST-03-33 .
- Asian Institute of Technology. Thesis ; no. ST-03-33 .
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology
Thesis (M.Eng.) - Asian Institute of Technology, 2003
Ha Noi, The Capital of Viet Nam, is situated in a region where the tectonic faults exist along the Hong (Red), Chay and Lo rivers in a northwest-southeastern direction. Studies show that Ha Noi is situated in the area where the average magnitude of earthquake is 6.1 (MSK scale) and the focal depth ranges from 15 km to 20 km. Therefore, it is urgent to conduct a detailed seismic hazard assessment of this area. Although there are studies about seismic microzonation for Ha Noi, the construction of microzonation map using Microtremor Technique was first time performing in this city. The map provides a basis for site-specific risk analysis, which can support the seismic risk reduction. Microtremor observations were carried out at 63 sites concentrated in Metropolitan Area of the City. The ground predominant periods were determined from the horizontal to vertical (HIV) spectral ratios of microtremors and a microzonation map was then constructed from variation of predominant period for Ha Noi. In addition, Equivalent Linear Analysis was also carried out for available soil profiles at different sites using SHAKE 91 software to verify the results from microtremors measurements. The study demonstrates that the Metropolitan Area of Ha Noi has considerable long predominant period. Besides it, the predominant period is found to increase from the North to the South direction. Thus, the study pointed out that the earthquakes might cause severe effects on the structures especially with long-span bridges or high-rise buildings around this area. The results of this study are expected to be helpful for a detailed hazard assessment of the Ha Noi.