第37回統計地震学セミナー / The 37th Statistical Seismology Seminar

When people and their environment are not properly prepared, earthquakes pose a serious threat. Recently, the SEISMO-12 earthquake scenario exercise simulated the repeat of the 1356 Basel earthquake.

This gave officials, organizations, and the general public an idea of what may be expected in case of a M6.6 earthquake. The present work relates to the scenario and contributes to loss reduction by expressing the potential impact through seismic risk. Reducing the short-term seismic risk requires the evacuation of vulnerable buildings. However, one cannot always evacuate in times of an ongoing seismic sequence.

Based on information of the continuous seismicity, probabilistic forecasts show increasing benefit for short-term defense against earthquakes. Forecast probabilities subsequently allow time-varying seismic hazard calculation. Only another combination with time-invariant loss estimation permits the assessment of short-term seismic risk.

Seismic risk delivers a more direct expression of the socio-economic impact than seismic hazard, but one must characterize vulnerability and exposure to estimate risk. Risk assessment brings together a variety of data, models and assumptions. Based on the specific earthquake scenario, I perform a probabilistic forecast of human losses. Seismologists may not be responsible for communicating short-term risk information to the public, but they have to support decision-makers to take worthwhile actions that may save lives. However, the low-probability environment and the complexity of involved processes challenge decision-makers. A final cost--benefit analysis constitutes greater benefit than pure statistical approaches by providing objective statements that may justify evacuations. To deliver supportive information in the simplest reasonable form, I propose a warning approach --- in terms of alarm levels --- which allows one to explore worthwhile mitigation actions for each district of the Basel region.