ICONE19-43163 DEVELOPMENT OF A METHODOLOGY FOR THE CHARACTERISATION OF LONG-TERM GEOSPHERE EVOLUTION : (1) IMPACTS OF NATURAL EVENTS AND PROCESSES ON THE GEOSPHERE EVOLUTION OF COASTAL SETTING, IN THE CASE OF HORONOBE AREA

Abstract

A critical issue for building confidence in the long-term safety of geological disposal is to demonstrate the stability of the geosphere, taking into account its likely future evolution. This stability is broadly defined as the persistence of Thermal-Hydrological-Mechanical-Chemical conditions considered favourable for the long-term safety of a geological repository. This study provides the conceptualisation and preliminary results of numerical simulations of the long-term geosphere evolution, especially groundwater flow properties, in the Horonobe area, Hokkaido, northern Japan, based on data from the JAEA's underground research laboratory project. Information on natural events and processes has been integrated into a chronological conceptual model, which indicates space-time sequences of the events and processes in the Horonobe area over geological time. Spatial scale for the numerical simulations are based on the recharge and discharge area in the present and the past glacial periods, and the direction of the groundwater flow in the present of Horonobe area. Time scale for the numerical simulations over the last 1.5 million years are defined by the palaeogeography of Horonobe area, and mainly focused on the changes of the geological structure (i.e. hydrogeological structure), recharge rate, and distribution of sea and land area caused by sub-surface and earth-surface processes such as crustal movement, climatic and sea-level changes. The results of the simulation show that the range and magnitude of change in groundwater flow properties, and sensitivity of the properties to the sea-level and elevation changes due to crustal movement have close relationship with the distribution and the evolution of the hydraulic conductivities of geological formations.