Large-scale ground motion simulation of the 2016 Kumamoto earthquake incorporating soil nonlinearity and topographic effects

A large-scale physics-based simulation is conducted to investigate ground motion distribution in the M-w 7.0 2016 Kumamoto earthquake, Japan. The model simulates the earthquake scenario from fault rupture to wave propagation, and localized site response with consideration of the combined effect of soil nonlinearity and topographic amplification. The simulation domain is 51 km x 43 km x 25 km, and the obtained ground motion time histories are compared satisfactorily with recordings from KiK-net and K-NET. Ground motion distribution considering nonlinear soil response and topographic amplification is presented. A 3D equivalent linear model is developed to mimic the soil nonlinearity, and it is demonstrated that neglecting soil nonlinearity could over-predict peak ground acceleration (PGA) and underestimate peak ground velocity (PGV) near the fault. The topographic amplification factors (TAFs) of PGA and PGV are found between 0.5 and 2.0, with a correlation coefficient of 0.7 between them. Predictive equations are proposed to correlate TAFs of PGA and PGV with topographic features, which are represented by relative heights obtained at different length scales. Finally, major earthquake damages are summarized with reference to the obtained ground motion intensity map.

Automated summary

A large-scale physics-based simulation was conducted to investigate the ground motion distribution in the 2016 Kumamoto earthquake in Japan with a magnitude of M-w 7.0. The simulation considered fault rupture, wave propagation, and localized site response, taking into account the combined effect of soil nonlinearity and topographic amplification. The obtained ground motion time histories were compared satisfactorily with recorded data. The study presented the ground motion distribution considering nonlinear soil response and topographic amplification, and developed a 3D equivalent linear model to mimic soil nonlinearity. Neglecting soil nonlinearity could result in overestimating peak ground acceleration (PGA) and underestimating peak ground velocity (PGV) near the fault. The study also found topographic amplification factors (TAFs) of PGA and PGV between 0.5 and 2.0, with a correlation coefficient of 0.7 between them. Predictive equations were proposed to correlate TAFs of PGA and PGV with topographic features.