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Crustal deformation is closely associated with hazard risks. We have developed a crustal deformation visualization system for understanding the relationships between contemporary crustal deformation and geographical information such as topography, stratigraphy, and land use. The system is composed of three major functions. The terrain is visualized by a 3D map with arbitrary maps such as aerial photographs and elevation contour maps. A graphical user interface is provided to explore the 3D visualization. If GNSS are classified into several groups of similar velocities, they are indicated by colored symbols on the 3D terrain map, which underline major GNSS velocity discontinuities. Furthermore, every GNSS time-series evolution is displayed by animation. This intuitive data visualization system contributes to both scientific applications and geography classes on earthquake hazard study in primary and secondary education.

A method to construct the history of past crustal deformation based on diatom analysis was developed, and the amount of coseismic and postseismic deformation associated with the 17th Century megathrust earthquake in Toberi marsh, Tokachi, Hokkaido, was estimated. The cores including the tsunami deposits at an altitude of 2.5-3.0 m (TP) inferred that subside trend continued before the earthquake and it turned to uplift trend after the event. Since both of the trends are gradual, the coseismic deformation does not seem to be significant. On the other hand, Pseudopodosira kosugii, which distributes the intertidal to supratidal zone, is most abundant on the horizon of the tsunami deposits. Present habitat distribution of Pseudopodosira kosugii in the same marsh revealed that the upper distribution limit and mode were 0.8 to 1.3 m (TP) and -0.2 to 0.3 m (TP), respectively. Prehistorical uplift can be estimated from the current elevation of the limit and the mode of this diatom in the core. The amount of the uplift in Toberi march after the 17th Century event was ca. 1.5 m. That was constrained by using both the distribution limit and the mode of cores from five survey points in the marsh. Information about the crustal deformation after the 17th Century event is useful for the evaluation of source models of the earthquakes that is used for tsunami hazard assessment along the Pacific coast of Hokkaido., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The ecologies (salinity tolerance) of many diatoms are largely unknown, despite their potential to contribute to more detailed paleoenvironmental reconstructions. This study therefore aimed to investigate the relationship between diatom species and salinity. We cultured seven cosmopolitan benthic diatom species obtained from Lake Akan, a freshwater inland lake in Japan: Epithemia adnata, E. frickei, E. gibba, E. operculata, E. sorex, E. sp. and E. turgida. Each species was cultured at eleven salinities between 0‰ and 50‰. Epithemia adnata, E. frickei and E. sorex had the highest growth rate at a salinity of 3‰, with no further increase observed above 25‰. However, E. gibba had the highest growth rate at a salinity of 5‰, with no increase at salinities ≥ 30‰. These results suggest that E. adnata, E. frickei, E. gibba, and E. sorex grow in freshwater to brackish-water environments. Epithemia operculata and E. sp. proliferated at all salinities, indicating that they can adapt to hypersaline environments. However, E. turgida did not survive in salinities >10‰, making it the species with the narrowest salinity tolerance range. These results provide new knowledge that improves the understanding of the ecology of these species in modern environments and offer insights into paleoenvironmental reconstructions through diatom analysis.