The Geological Survey of Japan has issued about 50 reference materials over the past 50 years. They have been used all over the world to improve the reliability in chemical analysis of geological materials. Geological samples of rocks, ores, minerals, soils, sediments, etc. generally contain various elements at high concentration levels. For accurate chemical analysis, it is necessary to use geochemical reference materials that contain major components at similar levels to the samples to be analyzed and predetermined concentrations of target elements. In this paper, scenarios to develop geochemical reference materials for Japan and the rest of the world are described. Methods for selecting and grinding sample materials, the determination of reference values, and data sharing are also reported.
Although geoinformation pertaining to urban areas is very important, paper-based geological maps do not adequately describe the subsurface geological conditions of urbanized plains. A three-dimensional geological map, available via the Internet, is expected to provide intelligible, highly reliable, and easily utilizable geoinformation for urban areas. In this case, a three-dimensional geological model needs to be constructed on the basis of reliable borehole data using an advanced modeling tool. We are now developing a prototype of a three-dimensional geological map of the northern part of Chiba Prefecture as a new form of urban geoinformation which contributes to estimating the risk of geological disasters.
Our final goal is to provide quantitative information on subsurface S-wave velocity structures in response to a variety of social needs regarding geological and soil matters. Since S-wave velocity is a physical property directly related to site amplification and ground stiffness, it is expected to contribute to, for example, improving accuracy of seismic zoning for the mitigation of earthquake disasters. Currently, we are constructing a system for observation and analysis of microtremors to explore S-wave velocities within the depth range from several to tens of meters on the basis of 15-minute observations with a miniature seismic array having a radius of 0.6 m. The simplicity and objectivity of our system affords automization and quality control, with an expected capacity to acquire large amounts of microtremor data.
The reliability of earthquake forecast information is important for disaster mitigation in our society. A physical model of the earthquake generation process was constructed to improve the reliability of earthquake forecast information. We proposed a model based on the information extracted from geological surveys. Our model was evaluated using experimental techniques in the laboratory. During the experimental study, we considered two disparities between laboratory and natural conditions, which were differences in environmental conditions and timescale. A new experimental rock deformation technique was developed that unifies previous and newly developed techniques. Long-term geological processes were evaluated by a process model operating over a compressed timescale.