The influence of pulse-like ground motion on landslide triggering during the 2016 M_w 7.1 Kumamoto earthquake

抄録

The 2016 M_w 7.1 Kumamoto earthquake induced widespread landslides, predominantly in the Aso area, approximately 20 to 40 km from the epicenter. Pulse-like ground motion (PLGM) was observed in this area. To understand the landslide causation in this event, we hypothesize that the velocity pulse of PLGM is the critical factor in triggering landslides. Firstly, the PLGM in the widespread landslide area is identified. Secondly, the characteristics of typical PLGM waveforms are analyzed. Finally, the Aso-Bridge landslide is taken as a case study to analyze the influence of PLGM on triggering landslides. The results indicate that the velocity pulses of PLGM have significant velocity amplitudes even though the acceleration is small. Moreover, the velocity pulses make up the major energy of these PLGM. Also, the simulation results of Aso-Bridge landslide show that both the original and extracted pulse motion can initiate landslides, whereas the residual ground motion cannot, thus validating the proposed assumption. Furthermore, high-frequency residual ground motion is difficult to trigger landslides even though the PGA is large, but its energy and PGV are low, indicating the limitation of slope stability analysis only considering the PGA.