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Large-scale landslides along the Kubusu and Besso rivers in Toyama Prefecture are developed in the Miocene Iwaine Formation, which is composed of andesitic lava, tuff, and tuff breccia. In the middle member of this formation, the tuff is easily altered to montmorillonite-bearing rock, and subsequently plays an important role in the development of landslides events, which tend to be large-scale events, as the massive lava of the upper member forms a cap rock over the tuff. The Kiritani and Koinami basins, which are flat intermontane basins located along the Kubusu and Besso rivers, respectively, are interpreted as landslide-dammed lakes, later filled with sediment. Accelerator mass spectrometry C ages show that the landslides forming each dam occurred simultaneously, at approximately 2500 BP. These ages were measured from wood fragments embedded in the landslide material of Kiritani, and from an in situ stump drowned during the impoundment of Koinami. If the trigger of these landslides was an earthquake, it is most likely to have been the penultimate event along the Atotsugawa fault zone. [ABSTRACT FROM AUTHOR]

Background: Although the circumstances surrounding falls among community-dwelling elderly people have been described by numerous studies, there are few that have reported falls in the northern regions of Japan, such as Hokkaido, that experience a severe winter with heavy snow. As a preliminary study, we surveyed the circumstances of falls among community-dwelling elderly people in Hokkaido with a self-administered questionnaire. Methods: Residents living in private homes throughout Hokkaido were randomly contacted by telephone and those aged over 65 years were recruited for this study. In all, 1000 subjects participated in the survey. A questionnaire was used to obtain the histories of falls, including the number of falls, the season and place of occurrence, and the cause of the falls in the year prior to the survey. Results: Of the 1000 subjects, 849 (436 men and 413 women; mean age, 73.0 years) completed the questionnaire. Among the 849 subjects, 277 (32.6%) fell at least once during the year of the survey. Of these 277 subjects, 155 subjects (56.0%) experienced two or more falls in the year. Approximately 60% of the falls occurred during the winter. The most common location where falls occurred was on roads or sidewalks, and slipping was the most prevalent cause. Conclusion: Our findings revealed several aspects regarding the circumstances surrounding falls among community-dwelling elderly people in Hokkaido. [ABSTRACT FROM AUTHOR]

Earthquakes are considered to be important triggers of deep-seated gravitational slope deformation (DGSD) in seismically active regions, and if that is the case, DGSD features could be candidates for off-fault paleoseismology investigations. On the basis of pit excavations and sediment cores at an off-fault DGSD site and a trench excavation across the active Neodani fault at a nearby site, we examined the records of DGSD and surface-rupturing paleoearthquakes of the Neodani fault. The four most recent DGSD events were dated at after 240 cal BP, 1710–340 cal BP, 4730–3970 cal BP, and 5570–5340 cal BP. The four most recent surface-rupturing earthquakes were dated at 1891 CE (the Nobi earthquake), 2010–1220 cal BP, 7180–2110 cal BP, and before 9540 cal BP. We conclude that the ages of the four DGSD events are consistent with surface-rupturing earthquakes on the adjacent Neodani fault. We infer that static crustal strain from repeated seismogenic faulting plays an important role in the occurrence of DGSD events, at least in the immediate vicinity of active faults, although coseismic severe shaking would have at least some effect on them. Our case study suggests that off-fault DGSDs can be used to reconstruct or refine the paleoseismic history of a nearby active fault. We propose that an ideal DGSD for that purpose would be located in an area of concentrated strain near a termination, bend, or stepover of the target fault. Unlabelled Image • Synchroneity between off-fault DGSD events and adjacent paleoearthquakes was shown. • Static crustal strain plays an important role on the triggering of DGSDs. • DGSDs have a utility of off-fault paleoseismology under mountains conditions. [ABSTRACT FROM AUTHOR]