High-frequency strong ground-motion simulation for the 2016 Mw 7.0 Kumamoto earthquake

The 2016 Kumamoto earthquake Mw 7.0 occurred in Japan reveal a multisegment shallow fault rupture that was well recorded by the KiK-net stations in accelerographs placed inside boreholes and on the surface. The numerous damaged buildings due to this earthquake reflect the critical implications for seismic hazard estimation and improvement of earthquake-resistant design for a shallower event. Here, we generate synthetic accelerograms at high frequencies implementing a stochastic method that allow us to simulate horizontal and vertical strong ground-motion accelerograms in azimuthal well-distributed stations. We included multisegment finite fault geometries estimated by independent authors as input for source model. From each sub-fault we calculated the incident and azimuthal angles arriving at each seismic station, we determined free surface effect, energy partition, radiation pattern and dynamic frequency corner for sources effect. Besides, we adopted region-specific attenuation parameters such as geometrical spreading and anelastic attenuation for path effect, and site effect parameters such as generic amplifications, soil amplification transfer functions for body waves, and high-frequency attenuation kappa filter. Our simulated acceleration time series show similarities in time and frequency with the observed records in the frequency band between 1 – 10 Hz. We obtained a good agreement between peak ground accelerations for both horizontal and vertical components, and we reproduce the amplitude and attenuation trend for the horizontal component of the GMPE models in the region. Finally, we are capable to simulate the high-frequency band of engineering interest using physics-based parameters to improve our knowledge about the source, path, and site effect and their impact on a seismic hazard assessment in earthquake-prone regions.