Challenge to Increase Confidence in Geological Evolution Models

Abstract:

The geological evolution models (GEMs) as well as site descriptive models (SDMs) are used to integrate investigation results and to support safety assessment. Even more, enhancing confidence in long-term stability of geological environment is required for geological disposal in Japan where is in active tectonic region. The aim of the study is to provide future direction for increasing GEMs confidence based on review of current GEMs.

GEMs has been constructed in following three steps; 1) Features, Events and Processes (FEP) analysis, 2) Scenario development and 3) Numerical modeling. Base on the current status, we looked at the issues for developing GEMs with higher level of confidence. As the result, development of techniques and methodologies for; 1) validation of GEMs, 2) handling uncertainty and 3) digitalization/visualization are identified as open issues. To solve these issues, we specified three approaches. First approach is using multiple lines of evidence. Consistency between various study fields will be important information for validation of the GEMs. Second one is revealing the argument behind GEMs. Confidence/uncertainty of GEMs will be able to be confirmed by synthesizing the basic information behind the GEMs because GEMs are built on many evidences, hypothesis and assumptions. In addition, the optional cases will be needed for demonstrating the level of understanding. Third is development of elemental technology, such as the integrated system between numerical simulation and visualization which can take into account large size of model and composite phenomenon. In the future, we will focus on increasing GEMs confidence in keeping with this notion.

This study was carried out under a contract with METI (Ministry of Economy, Trade and Industry) as part of its R&D supporting program for developing geological disposal technology.