4:35 PM - 4:55 PM
[HDS10-10] My landslide research: past and future
★Invited Papers
Keywords:landslide, geology, deep-seated gravitational slope deformation
I will retire at the end of March 2023. In this talk I would like to review my landslide research in the past and future.
Landslide and geology: One of the important factors determining the place of landslide is geology. Most of slides in the Chichibu belt, eastern Kii Peninsula occur on the northern slopes, because the rocks of the Jurassic accretionary complexes in the belt are dipping to the north and they slid on the dip slopes. Moreover, the P/T boundary black shale sandwiched between the hard chert formations and the unit-boundary faults formed during the accretionary processes, that makes the slipping planes, are also dipping to the north. The landslide sites are determined by the geology and geologic structure of the accretionary complexes.
Landslide and earthquake: The Kiritani and Koinami basins in the southern Toyama City were formed by reclamation of landslide-dam lakes. The AMS-14C ages of stumps embedded in the lake sediments and wood fragments enrolled along the slide surface are concentrated around 2,500 years BP. These ages suggest there was an event triggering these slides. It might be a large penultimate earthquake before the Hietsu earthquake in 1858 not detected by trench researches along the Atotsugawa fault.
Landslide and deep-seated gravitational slope deformation (DSGSD): Recent development of Lidar measurement techniques clarify that there are many topographic features characteristic of DSGSD in low-altitude mountains covered by thick vegetations. Such features are considered as precursors of deep-seated landslides. Most of the large-scale DSGSD in the Mino Mountains along the boundary between Gifu and Fukui Prefectures formed around 10,000 years ago. This fact indicates the many DSGSD topographies were formed under the wet and warm climate after the Last Glacial period; most of them were developed into the large landslides although some of them have been survived until now. The DSGSDs in this area are stable now and are not precursors of deep-seated landslides.
I would like to continue the DSGSD researches not only in Japan but also in the glaciated regions, like Swiss Alps, in future.
Landslide and geology: One of the important factors determining the place of landslide is geology. Most of slides in the Chichibu belt, eastern Kii Peninsula occur on the northern slopes, because the rocks of the Jurassic accretionary complexes in the belt are dipping to the north and they slid on the dip slopes. Moreover, the P/T boundary black shale sandwiched between the hard chert formations and the unit-boundary faults formed during the accretionary processes, that makes the slipping planes, are also dipping to the north. The landslide sites are determined by the geology and geologic structure of the accretionary complexes.
Landslide and earthquake: The Kiritani and Koinami basins in the southern Toyama City were formed by reclamation of landslide-dam lakes. The AMS-14C ages of stumps embedded in the lake sediments and wood fragments enrolled along the slide surface are concentrated around 2,500 years BP. These ages suggest there was an event triggering these slides. It might be a large penultimate earthquake before the Hietsu earthquake in 1858 not detected by trench researches along the Atotsugawa fault.
Landslide and deep-seated gravitational slope deformation (DSGSD): Recent development of Lidar measurement techniques clarify that there are many topographic features characteristic of DSGSD in low-altitude mountains covered by thick vegetations. Such features are considered as precursors of deep-seated landslides. Most of the large-scale DSGSD in the Mino Mountains along the boundary between Gifu and Fukui Prefectures formed around 10,000 years ago. This fact indicates the many DSGSD topographies were formed under the wet and warm climate after the Last Glacial period; most of them were developed into the large landslides although some of them have been survived until now. The DSGSDs in this area are stable now and are not precursors of deep-seated landslides.
I would like to continue the DSGSD researches not only in Japan but also in the glaciated regions, like Swiss Alps, in future.