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Seismic Models for the Taiwan Probabilistic Seismic Hazard Assessment: Tradition and Innovation

Description: 

To develop the official probabilistic seismic hazard assessment (PSHA) for Taiwan, the Taiwan Earthquake Model (TEM) updated earthquake catalogs and seismogenic structure databases to refine seismic source parameters. The areal sources surrounding Taiwan were divided into 30 zones to estimate seismic hazards, integrating seven earthquake catalogs spanning from 1900 to 2023. Background seismicity was calculated, based on the assumption of a Poisson distribution, after excluding foreshocks and aftershocks. Both onshore and offshore seismogenic structures were updated in the model, incorporating newly identified multiple-structure ruptures based on Coulomb stress criteria and historical evidence. The analysis procedure of this model meets engineering requirements and its outcomes contribute to advancing disaster prevention strategies in the public sector, including the development of earthquake scenarios, disaster evacuation plans, and rescue drills.

However, the assumptions of a traditional PSHA diverge from observed seismic behaviors. To address these challenges, we utilized the Seismic Hazard and Earthquake Rates in Fault Systems (SHERIFS) model, which accommodates multiple-structure ruptures and can anticipate larger seismic events than typically expected. The model not only reflects the occurrence of the 2024 M_w7.5 Hualien earthquake but also aligns with historical seismic activity. Moreover, traditional PSHA assumes events are independent, making it unsuitable for quantifying hazards arising from earthquake sequences. Recognizing the limitations of traditional models for short-term forecasting, we integrated the Epidemic-Type Aftershock Sequence (ETAS) model. Model credibility was validated by comparing predicted ground shaking exceedance probabilities with maximum observed ground shaking at strong-motion stations during a short observation period. These innovative methods highlight the importance of integrating multiple seismic models to achieve precise and comprehensive seismic hazard assessments.

Session: Advancing Time-dependent PSHA and Seismic Risk Assessment: Accounting for Short- to Medium-term Clustering - I

Type: Oral

Date: 4/15/2025

Presentation Time: 11:30 AM (local time)

Presenting Author: Chung-Han

Student Presenter: No

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