[S-CG40] Active Tectonics and Seismic Hazards in the Himalayan Region

[SCG40-P05] Characterization of Extreme Ground Motions

*三宅 弘恵¹ (1.Earthquake Research Institute, University of Tokyo)

Ground motion time history is one of the most important factors to judge whether ground motion prediction works well in the scenario-based seismic hazard assessment. To link seismology and earthquake engineering, ground motion response spectra became the first priority to validate broadband ground motions. Although the duration and phase information are useful to separate near-fault ground motions with rupture directivity pulses and long-period ground motions for similar ground motion response levels, ground motion response spectra are helpful to direct use for design basis ground motions. It is well known that ground motion pulses increase the response at the dominant periods that largely affect structures. The significant impact of ground motion pulse on response spectra is indicated for the 1992 Landers, 1995 Kobe, 1999 Kocaeli, 1999 Chi-Chi, 2015 Gorkha, 2016 Kumamoto, and other earthquakes. In theory, both duration and amplitude of ground motion pulse increase as a function of earthquake magnitude, therefore the upper bounds of response spectra are increasing as a function of period. Due to the accumulation of extreme ground motions with dense strong motion observations, empirical upper bounds of peak ground accelerations and peak ground velocities are still increasing due to seismic source complexity and strong site amplification. However, this study found the empirical upper bounds of response spectra exist and can be shaped by a few extreme ground motions of crustal and collusion earthquakes. On the other hand, many simulated ground motions for subduction earthquakes exceed the current empirical upper bounds of response spectra.