Vol.9 No.2 2016

Research paper : Three-dimensional urban geological map (T. NAKAZAWA et al.)−80−Synthesiology - English edition Vol.9 No.2 (2016) by general users as well as researchers and engineers who are familiar with printed map sheets. For the display of the 2D map, high-speed map display technology using tiled images is used to provide better operability for users. This technology allows zoom in/out and moving by mouse operation. For the display of cross-section diagrams, a vertical geological cross-section between two points identified by clicking on a 2D map can be displayed. For the display of 3D diagrams, since web delivery of a whole area model is difficult due to the file size of 3D geological model data, the whole area is divided into lattices and a model for each smaller region is displayed. For the borehole data, by clicking on the data point, the metadata can be browsed. The metadata includes the link to JACIC XML and PDF. By constructing a database of metadata and by adding the function of setting the search range to the browser system, the metadata of borehole data can be searched from the browser system.The borehole data for public works possessed by the local governments and the standard borehole data organized by AIST are important basic data that form the core of 3D modeling, and are essential information to maintain reliability of the 3D model. Therefore, we develop a system that allows the local governments to manage the borehole database in JACIC XML format (Fig. 7).[17] For the database, PostgreSQL,Term 6 that is an RDBMSTerm 5 with high versatility, is used, and this system will be released free of charge. Through the use of such a system, it is expected that the borehole data that is the basic geoinformation of urban areas will be appropriately managed in many local governments.4 Assumed utilization of a 3D geological mapCurrently, in our group, the six elemental technologies discussed in the previous chapter are being integrated, and we are attempting to create a 3D geological map. Assumed utilization of such a 3D geological map is in making hazard maps for earthquakes, planning for urban infrastructures and industrial constructions, and in real estate transactions.For the creation of an earthquake hazard map, the subsurface elastic wave velocity data (particularly S wave velocity data) and a shallow subsurface geological model are necessary.[18] However, existing borehole data that include S wave velocity data is rare. Since our drilling survey measures the S wave velocity, it can be used as the standard data for seismic motion simulation. Also, our 3D geological model created based on the standard borehole data is also expected to be used as geological model data when creating earthquake hazard maps (Fig. 8). Moreover, by understanding vibration characteristics such as specific dominant frequencies of the ground by microtremor measurement,[19] it is possible to create earthquake hazard maps that accurately take the geology into consideration. Therefore, our group conducts microtremor measurement along with the construction of the geological model, and we are considering classification of ground vibration characteristics according to geological conditions.In planning urban infrastructures and industrial construction, it is extremely important to collect information beforehand on the presence of weak ground and at what depth the stratum that would be the support base of the structure is distributed. If this information can be known beforehand, the planning and estimates of the geological survey can be done easily. In the geological survey industry, efforts are spent on reducing the risks of delay of survey periods, design change, or increased project costs that may occur if the geological condition is different from the one assumed.[20] As a measure, the existing geoinformation should be actively used.[21] The existing borehole data of the urban areas and a 3D geological model appropriately interpreted from such data are thought to contribute to risk management through disclosure in an easy to use format (Fig. 8).Since the 2011 Off the Pacific Coast of Tohoku Earthquake, Format conversion programConvert from local government’s file format to standard formatBorehole data management systemData searchDisplay metadataDisplay and edit borehole logCheck entered data on background of various mapsData management by databaseFig. 7 Conversion program for the borehole data and its management system


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