Time-Dependent Seismic Hazard Assessment for the Taiwan Region: New Conception and Ideas for Seismic Risk Management

The paper describes an integrated approach to seismic hazard assessment, which was applied for the Taiwan region. First, the theoretical seismic catalogue (2001-2050) for the Taiwan region had been calculated using the 4D-model (location, depth, time) for dynamic deformation of the Earth’ crust and 5D-model (location, depth, time, magnitude) for seismic process. The models were developed on the basis of available geophysical and geodynamic data that include regional seismic catalogue. Second, empirical models for ground motion estimation in the region were obtained on the basis of records from recent (1993-1999) earthquakes. The database includes strong-motion data collected during the recent Chi-Chi earthquake (M=7.6, 21 September 1999) and large (M=6.8) aftershocks. The ground-motion database was also used for evaluation of generalized site amplification functions for typical soil classes (B, C and D). Third, the region & site & time-dependent seismic analysis, which is based on schemes of probable earthquake zones evaluated from the theoretical catalogue, regional ground motion models, and local site response characteristics, has been performed. The seismic hazard maps are compiled in terms of Peak Ground Acceleration (PGA) and Response Spectra (RS) amplitudes. The maps show distribution of amplitudes that will not be exceeded with certain probability in condition of typical soil classes during all possible earthquakes that may occur in the region during time period of 2003-2025. The approach allows introducing new parameter that describes dependency of seismic hazard on time, so-called “period of maximum hazard”. The parameter shows the period, during which every considered site will be subjected by the maximum value of ground motion characteristic (PGA or RS). In general the approach may be considered as estimation of “Real Seismic Hazard”, which is based on parameters of future earthquakes and, at the same time, which utilize information obtained during earthquakes that did occur.