[en] 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. The research activity in fiscal year 2008 composes of the following contents. Concerning earthquake and fault movement, we continue to develop investigation techniques for evolutional history and activity of fault, and carry out case studies for development of effective assessment model in the fault zones. For volcanological and geothermal studies, we plan to provide an integrated approach 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. Concerning uplift, denudation, climatic change and sea-level change, we plan to arrange investigation techniques for reconstruction of paleo-topography and paleo-climate, and to establish a simulation model for landform development. For study on the long-term stability of the geological environments, we plan to accumulate knowledge about hydrothermal activity, and to develop simulation techniques for groundwater flow related by crustal movement, etc. In addition, we develop analytical methods that is necessary for these studies. (author)