Near real-time, time-dependent estimates of the likelihood of earthquake-induced mass-movements in the Valais and associated impacts

Abstract

Earthquake-induced mass movements are a substantial threat to mountainous areas in seismically active regions like the Valais, the most seismically hazardous region of Switzerland. This study describes a comprehensive procedure to deliver short-term time-dependent predictions of mass-movement likelihoods in the Valais and their impacts in near real-time during major earthquake sequences. We rely on the availability of a Swiss-specific empirical model for the prediction of seismically-induced mass-movement likelihood, and combine it with rapid probabilistic earthquake shaking estimates based on short-term seismicity forecasts following a triggering seismic event, and state-of-the-art input models to probabilistic seismic hazard studies in Switzerland. The aftershocks are spatially distributed in proximity to the triggering event, in a volume that can accommodate the largest possible source in the aftershock sequence. The procedure is developed and demonstrated based on the possible repetition of relevant historical and instrumental sequences in the region. The obtained probabilities of mass-movement are spatially associated with exposed assets in the region to estimate the associated risk. We propose a strategy for optimal communication of risks emerging from earthquake induced mass-movement hazards, providing stakeholders with alarm levels and other decision-making tools based on risk-cost-benefit considerations for critical lifelines. Fully automated and largely customisable, the procedure can be easily extended to the greater Swiss region and integrated within the evolutionary earthquake shaking information systems of the Swiss Seismological Service.