Time-Dependent Probabilistic Seismic Hazard Assessment in Complex Fault Systems: Exploring the Longitudinal Valley of Taiwan

This study validates several seismic models with long- and short-term forecasting capabilities used in probabilistic seismic hazard assessment (PSHA) and evaluates their impact on hazard levels in the Longitudinal Valley, Taiwan, a region characterized by high seismic activity and data quality. The Gutenberg-Richter (G-R) law demonstrates good fitting performance for the long-term rate in small to moderate magnitudes, while the pure characteristic earthquake (PCE) model, which assesses the maximum recurrence rates for individual seismogenic structures, better fits the long-term rate for large magnitudes. The Seismic Hazard and Earthquake Rates in Fault Systems (SHERIFS) model integrates the G-R law and structural parameters while considering multiple fault ruptures. It performs well in forecasting long-term seismicity rates, particularly for medium to large magnitudes. Recognizing the limitations of long-term seismic models in short-term and aftershock forecasting, we further incorporate the Epidemic-Type Aftershock Sequence (ETAS) model to analyze short-term earthquake occurrence rates and assess the temporal evolution of seismic hazard. The model is validated using the maximum ground shaking observed at strong-motion stations during the given short observation period. The ETAS model complements existing approaches by providing more immediate forecasts of seismic activity. Our findings provide hazard assessment results across different time scales and underscore the importance of integrating multiple seismic models for precise seismic hazard assessment. This study offers valuable insights into earthquake processes and provides essential parameters for future PSHA studies in Taiwan.