AIST has published a next-generation geological map “Urban Geological Map of Central Tokyo (Special Wards Area)”. It visualizes the subsurface geological structures beneath central Tokyo to a depth of tens of meters in three dimensions.
It was difficult to accurately express subsurface geological structures beneath urban areas with conventional planar geological maps. Analysis of large amounts of survey data from as many as 50,000 sites with originally developed 3D modeling technology enabled to visualize the detailed subsurface geological structure of central Tokyo in three dimensions. As a result, the distribution of a valley-filling soft stratum called the post-Last Glacial Maximum (LGM) deposits in the lowlands of downtown Tokyo was depicted in great detail. Furthermore, it was clarified that a weak stratum similar to the post-LGM deposits is also distributed in a part of the Musashino Upland in the Yamanote area, which had generally been considered hard ground. This 3D geological map can be easily viewed by anyone free of charge, so widespread use is expected such as for earthquake hazard maps and urban infrastructure development in central Tokyo (special wards area). The map was released on the “Urban Geological Map of Central Tokyo” page of the AIST website on May 21, 2021.
3D image of the subsurface geology of central Tokyo, shown as “Urban Geological Map” on the AIST’s website
AIST published "Geochemical and risk assessment map of subsurface soils" of Shikoku region. The method of selecting the analysis points was vastly improved to expand the scope of the survey. Specifically, the analysis points were selected by comprehensively analyzing geospatial information such as surface geology, river basins, soil, and geo-history information, which enabled to successfully obtain geochemical information with the highest accuracy possible. This information was used to clarify the concentration distribution of twelve heavy metal elements such as chromium and arsenic (Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Cd, Sb, Pb, U) in the surface soil of the Shikoku region, and to conduct risk assessments of the effects on the human body. The results showed that while heavy metals exceeding environmental standards were detected in mountain areas, the level of risk to the human body was not a concern in current land use.
The geochemical and risk assessment map was released on the AIST: Geological Survey of Japan website from March 30, 2021 (URL：https://www.gsj.jp/Map/JP/soils_assessment.html).
Soil map of Shikoku region on Google Earth: Soil classification shown by colors in legend.
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