17:15 〜 18:45
[HTT14-P06] The 2018 Iburi Co-seismic Landslides, Assessing the slipping planes beyond Topographic Data: High-Resolution UAV-based Topography and Subsurface Geophysics
キーワード：Slope stability, Landslide, Iburi Earthquake, Hokkaido, Ground Penetrating Radar, UAV-based photogrammetry
From the infinite slope model to more complex FEM modelling of landslides, the position of the slipping plane is arguably one of the most important factors to be determined in the field, before and in the aftermath of an event. If deep-seated landslides often need coring and other geophysical analysis for slipping-plane determination, shallow landslides leave an apparent slipping plane at the surface, as could be seen during the 2017 rainfall landslides and the 2024 Noto Peninsula and the 2018 Iburi co-seismic landslides for instance. The large spatial extent and the sheer number of landslides have thus driven scientists to use remote sensing, in order to characterize the slipping planes. However, it is logical to wonder whether the apparent surface is the true slipping plane, or if it is one of the surfaces that contributed to sliding? Are we looking at the slipping plane, the same way we do with fault lines, as a 2D line on a map, instead of thinking of it as a volume? Should the word be "surface of rupture" or "volume of rupture"?
To test this hypothesis, the authors have conducted a set of field surveys in the area impacted by the 2018 Iburi earthquake in Hokkaido, using a combination of high-resolution RTK-UAV drone imagery for SfM-MVS purposes combined with aerial LiDAR data and Ground Penetrating Radar (800 MHz shielded antenna from 1,000 volts pulses).
Results have shown that the post-even surface could be a mixture of (1) a real slipping plane with no sign of lower crack or movement, meaning that the movement that occurred over the residual plane has all been evacuated; (2) the material remaining is overtopped by material that accumulated after or at the end of the slope's translation; and (3) finally the apparent surface slipping plane has also been shown to just be "one of" the slipping planes, as others exist underneath.
As the present survey occurred in one set of landslides that occurred in a sub-watershed drained by a single gully, the coincidence of the slipping plane with the present surface is not (at least in the present case) the results of the effect of spatial variability on the type of landslides but rather the product of local sliding and flowing parameters that still need further investigation.
To test this hypothesis, the authors have conducted a set of field surveys in the area impacted by the 2018 Iburi earthquake in Hokkaido, using a combination of high-resolution RTK-UAV drone imagery for SfM-MVS purposes combined with aerial LiDAR data and Ground Penetrating Radar (800 MHz shielded antenna from 1,000 volts pulses).
Results have shown that the post-even surface could be a mixture of (1) a real slipping plane with no sign of lower crack or movement, meaning that the movement that occurred over the residual plane has all been evacuated; (2) the material remaining is overtopped by material that accumulated after or at the end of the slope's translation; and (3) finally the apparent surface slipping plane has also been shown to just be "one of" the slipping planes, as others exist underneath.
As the present survey occurred in one set of landslides that occurred in a sub-watershed drained by a single gully, the coincidence of the slipping plane with the present surface is not (at least in the present case) the results of the effect of spatial variability on the type of landslides but rather the product of local sliding and flowing parameters that still need further investigation.