Large landslide at W Yataro Pass detected by ALOS-2 data pixel offset analysis, triggered by the 2024 Noto Hanto Earthquake (M7.6)

National Research Institute of Earth Science and Disaster Resilience (NIED) revealed many landslide landform at NE Noto Peninsula, Japan. M7.6 main shock occurred there on 1 Jan 2024, and Geospatial Information Authority of Japan (GSI) revealed that many landslides were triggered by the 2024 earthquake. Previous study also revealed the landslide was reactivated by the 2024 earthquake at W Yataro Pass located ca. 10km SW from the epicenter. We calculated 3D displacement at 12m in resolution by pixel offset using ALOS-2 ascending data, measured on 26 Sep 2022 and 1 Jan 2024, and ALOS-2 descending data, measured on 6 Jun 2023 and 2 Jan 2024. Because remarkable crustal deformation, e.g., uplift more than 4m occurred along the northern shore of the peninsula, the 3D crustal-deformation amount was estimated, and it was deducted from the calculated 3D displacement, and resulting 3D landslide displacement amount was obtained. The estimation was performed as follows; the calculated 3D displacement data were resampled into 120m, then the resampled displacement amount was clipped by the non-landslide landform produced from the database and the non-landslide triggered by the 2024 earthquake. Then, the displacement amount was estimated for all over the peninsula including the non-landslide landform and the non-landslide triggered by the 2024 earthquake at 12m in resolution, as applying Kriging method. Finally, we obtained NS, EW, and up-down (UD) component of the landslide displacement amounts at 12m in resolution. The previous study revealed that the large reactivated by the 2024 earthquake at W Yataro Pass moved from N to S, we expressed NS and UD displacement profile vectorially along the measurement lines. As a result, it was found that surface landslide body moved not only synclinal dip direction from N to S but also synclinal anti-dip direction from N to S, and at the S end of the edge of the synclinal structure disrupted landslides occurred along the landslide body. At the N end of the edge of the synclinal structure, continuous cracks appeared on the landslide body and we sampled charcoal at the outcrop of the crack. According to the carbon 14 dating of the charcoal indicated 2,500-2,100 BP year, we think that the previous iterated earthquake occurred in 2,500-2,100 BP year at the same magnitude of the 2024 earthquake and induced large landslide such as the landslide in this case. This study used KAKEN 23K00972.  The ALOS-2 data used in this study was given by JAXA, through the support of ERI JURP 2024-B-02 in Earthquake Research Institute, the University of Tokyo.