Estimation of site response during the 2016 Chauk, Myanmar earthquake based on microtremor-derived S-wave velocity structures

摘要

Microtremor measurements are conducted in the historical area of Bagan, Myanmar, which was damaged by the 2016 Chauk earthquake, in order to analyze the site responses in the affected area. Shear wave velocity structures at the observation sites are estimated by inversion analysis of the microtremor horizontal-to-vertical spectral ratios based on the diffuse field assumption considering the results of existing seismic refraction surveys. The seismic response analysis is performed in order to estimate ground motion intensities in the Bagan area during the 2016 earthquake using the seismic observation record obtained at Nyaung-U and the estimated Vs structures. The present study reveals the pattern of the ground motion intensities during the earthquake and shows that the peak ground accelerations vary approximately 90-170 cm/s(2) in the affected area. We also found no remarkable dependence of the ground motion intensity and the reinforcement after the 1975 earthquake on the monument damage grade.