Annual report for research on long-term stability of geological environments in FY2006

The Japanese islands are located in the tectonically active Circum-Pacific Mobile Belt. As a result, Japan has a high frequency of earthquakes and eruptions. The concept of geological disposal of HLW in Japan is based on a multi-barrier system which combines a stable geological environments with an engineered barrier system. Therefore, special consideration is given to the long-term stability of the geological environments, taking into account volcanism, faulting, uplift, denudation, climatic change and sea-level change in Japan. Development of investigation/evaluation technologies for geotectonic events has been carried out to evaluate the long-term stability of the geological environments in Japan. In fiscal year 2006, we carried out the following researches, to confirm existence of the phenomena that have influences on geological disposal system (e.g., active faulting, volcanism), and to develop the investigation techniques to reconstruct the history of these phenomena. For studies of active faulting and seismic activity, we reviewed the existing techniques to research past activities and distribution of active faults (migration, extension, development process of a deformation zone). For volcanological and geothermal studies, we extracted a technique for detecting crustal magma and/or geothermal fluid in deep underground using geophysical and geochemical data, and models assessing the likelihood of future volcanism and its influence on geological environments. For studies of uplift/denudation and climatic/sea-level change, we constructed conceptual models such as landform development model. (author)