Analyses of Building Damages in Mashiki Town in the 2016 Kumamoto Earthquake

Abstract

To analyze why a lot of buildings collapsed in Mashiki town by the 2016 Kumamoto earthquake, we compared the distribution of collapsed buildings with the construction years, the result of microtremor measurements of the ground, and the earthquake ground motions. The collapsed buildings and the construction years were judged from some aerial photographs. This study reveals that the damaged area shapes like a band, and the band caused by the foreshock is different from the band caused by the main shock. The collapsed building ratio is closely related to the maximum value of the pseudo velocity response spectrum calculated by the earthquake ground motion. The severest area includes many collapsed wooden buildings built after Order for Enforcement of the Building Standard Act amended in 1981. In the same area, the ratios of the collapsed buildings built before 1982 and after 1982 are almost same.