Estimation of Long Period Ground Motion Earthquake Effects to High-rise Buildings at Hanoi and HoChiMinh Cities, Vietnam

Abstract

Estimation of dynamic characteristics of subsurface such as predominant period, amplification factor, shear wave velocity play an important role in researchs of the effects of long-period ground motion earthquakes on high-rise buildings in big cities. However, in Vietnam, due to the lack of observation devices, there is a shortage of dynamic ground information. Consequently, in this paper, at first, the results of applying the Nakamura Method to data processing of microtremor observations in Hanoi and HoChiMinh City of Vietnam are presented. By using this method, the predominant period of the ground at the sites could be estimated from the horizontal to vertical (H/V) spectral ratios of microtremors. The obtained results show that the grounds of the mentioned two cities have considerable possibility of resonating with long-period ground motions. Then, the spectral accelerations in bedrock of Hanoi and HoChiMinh city were estimated by attenuation relationship of Uchiyama and Midorikawa 2006 with the far-source rupture faults that were Sumatra earthquake 2004 and Tha-Khaek fault line in Thailand. Next, the accelerations on ground surface of the above two Vietnamese cities were calculated by using spectral ratio of microtremor and inverse Fourier transform. Finally, those obtained accelerations were used to do the time history analysis applied for 8 high-rise buildings in Hanoi and HoChiMinh city. The results of this final step show that far-source rupture faults have considerable possibility to generate long-period ground motions that cause certain affects to the behaviors of high-rise buildings in Vietnamese cities.