[M-GI31] Earth and planetary informatics and data utilization

[MGI31-P07] Development of three-dimensional geological information of the southeastern part of Saitama Prefecture using borehole data

*Susumu Nonogaki¹, Keiya Yoneoka¹, Tsutomu Nakazawa¹, Junko Komatsubara¹ (1.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology)

Keywords:Geological information, Three-dimensional geological model, Borehole data

Shallow subsurface geological information plays an important role in evaluating geological risk in urban areas, such as liquefaction/subsidence and ground motion amplification. As part of the intellectual infrastructure development, Geological Survey of Japan (GSJ) are working on developing geological information, called the three-dimensional Urban Geological Map (3DUGM), that shows detailed 3D shapes of geological strata in the shallow subsurface areas using borehole data. To date, the 3DUGMs of the northern area of Chiba Prefecture and central Tokyo have been developed and are available for free on the GSJ website "Urban Geological Map" (https://gbank.gsj.jp/urbangeol/). In this presentation, we will provide an overview of our newly developed 3DUGM of the southeastern part of Saitama Prefecture, focusing on its creation process and the functionalities available on the website. In the 3D mapping, firstly, we established a standard stratigraphic framework for target area by carrying out drilling surveys and laboratory works and collected borehole data obtained from drilling surveys for public construction works, cooperating with local governments. Next, based on the standard stratigraphic framework, we identified basal positions of the eight geological strata distributed up to several tens of meters depth in target area for each borehole data and estimated the 3D shapes of basal surfaces for each geological stratum. Then, by combining the shapes of basal surfaces, we constructed a surface-based 3D geological model that shows the shallow subsurface geological conditions in detailed and released this 3D geological information on the Web. On the GSJ website, the surface-based 3D geological model can be visualized together with 3D representations of borehole data color-coded according to rock types and rock hardness. In addition, geological cross-sectional image along arbitrary line can be generated on the Web. These 3D geological information are valuable for better understanding of shallow subsurface geological conditions and are expected to make contributions to urban planning, development, and management by considering geological risk. The future works are to expand the range of 3D geological information development and to develop a seamless 3DUGM for the Tokyo metropolitan area by combining the 3D maps developed so far.