The certainty matrix for fault data and interpretations

• A method is presented to assess certainty in fault data and interpretations. • It is based on the matrix commonly used in risk assessment. • The method justifiable interpretations and decisions about faults to be made. This paper introduces an approach for expressing certainty in the analysis and interpretation of faults, using a modification of the risk matrix commonly used in risk assessment. The certainty matrix uses qualitative or semi-quantitative analyses of both the data used and an interpreted characteristic of individual faults or fault systems. These characteristics may include the existence of faults, the certainty of trace lengths, the age of faults, or the influence of faults on sub-surface fluid flow. This approach improves the ability to make justifiable interpretations and decisions about faults and fault-affected areas, including about issues relevant to geothermal energy exploration or the underground storage of radioactive waste. The use of this approach is illustrated using three faults from Somerset, UK.