The influence of pulse-like ground motion caused by the directivity effect on landslide triggering

Earthquake-induced landslides threaten human lives, infrastructure, and the environment. In 2016, the M w 7.1 Kumamoto earthquake caused widespread landslides. These landslides are mostly concentrated in the Aso area, which is in the forward direction of the fault rupture. Meanwhile, some pulse-like ground motion (PLGM) was identified in this area. To elucidate the reason for these landslides in the M w 7.1 event, we propose two assumptions: (1) The velocity pulse of PLGM is the critical factor in triggering landslides. (2) In the forward direction of fault rupture, the area with significant PLGM caused by the directivity effect corresponds with the widespread landslides area. In this study, first, the velocity pulse of the identified PLGM is extracted and analyzed. Then, to validate the first assumption, the slope failure under different ground motions is analyzed by the discontinuous deformation analysis (DDA). Additionally, to validate the second assumption, the ground motions induced by the M w 7.1 are simulated by the finite difference method (FDM). Moreover, the association between the distribution of ground motion parameters and widespread landslides is analyzed. As a result, this study indicates that the velocity pulse with larger energy contributes significantly to landslides. Moreover, this study also validates the distinctive directivity effect in the M w 7.1 event, which induces numerous PLGM and further increases the probability of landslides. Furthermore, the simulated ground motion parameters are more significant in the widespread landslides area. These results greatly support the two assumptions. This study provides an approach for slope stability analysis considering PLGM caused by the directivity effect. It is anticipated that the study can be greatly beneficial to potential landslide prediction in near-fault areas.