Rethinking seismic source model of probabilistic hazard assessment in Taiwan after the 2018 Hualien, Taiwan, earthquake sequence

We examined the performance of Taiwan earthquake model (TEM) PSHA2015. We retrospectively forecasted the seismic activities of the 2018 Hualien, Taiwan, sequence and proposed recommendations for the next generation of seismic hazard assessment for Taiwan. We confirmed the model credibility of the area sources by comparing with locations of the Hualien sequence and seismicity during the period from 2012 to 2016. We also concluded similar forecasting reliability for the smoothing model, which could be incorporated in the next generation of probabilistic seismic-hazard analysis (PSHA) as a branch of logic tree. To examine the performance of the seismogenic structure source model, we evaluated rupture probability of the Milun fault, which ruptured during the Hualien sequence. The TEM PSHA2015 model forecasts its rupture probability in 50 yrs as 53%, and the Brownian passage time (BPT) model forecasts 80%. The BPT model, considering also time-dependency rupture probability, is suggested for future hazard assessment, especially for the seismogenic structure sources with records of their last ruptures. This earthquake sequence has raised the importance of short-term seismic hazard assessment, which provides a basis for response after a devastating earthquake and/or forecasting consequence.