Abstract
In 2017, the Japanese government started a new operation system that issues earthquake forecasting information for the Nankai trough earthquake. However, the information will remain ambiguous in terms of where, when, and how large destructive earthquake occurs. Although this ambiguity is inevitable due to the uncertainties inherent to the information, the overall impacts to disaster mitigation are not well understood. We develop a new scenario method based on the idea of scenario planning approach to identify the effects and potential problems in utilizing the information for disaster mitigation. In this study, we constructed a scenario for a “slowslip” case where anomalous crustal deformation is observed but cannot be determined as precursor of the Nankai trough earthquake. The scenario described how and when the Nankai trough earthquake information is issued on the onset and development of anomalous “slowslip” crustal deformation and how the information is explained and disseminated through TV news media. Discussions among seismologists, journalists, and municipal officials for that scenario identified several unrecognized problems which could be caused by inconsistent responses between government and news media, demonstrating that the new method could be used in finding unexpected side effects associated with the Nankai trough earthquake information.
