NONLINEARITY AMPLIFICATION OF SUBSURFACE GROUND AT KIK-NET MASHIKI SITE DURING THE 2016 KUMAMOTO EARTHQUAKE

Abstract

 During the 2016 Kumamoto earthquake in Japan, a series of strong motions struck the towns along the active faults. The vertical array observation system at KiK-net Mashiki site installed by NIED observed a number of strong ground motions near the heavily damaged area. From the comparing between the weak ground motions and the strong ground motions mentioned above, nonlinearity of subsurface ground can be seen. In this study, the degree of nonlinearity in the amplification of subsurface ground was estimated from the inverse analysis of observed records. Quantitative relationships between the shear strains and shear modulus were obtained by the proposed method.