[S-GD01] Geodetic Advances in Crustal Dynamics and Environmental Change for Taiwan and Neighboring Regions

[SGD01-05] Integration of seismo-geodetic moment rates for earthquake forecasting with an emphasis on strain rate analysis in southwestern Taiwan

*Neha Neha¹, Ray Y. Chuang¹, Takuya Nishimura², Zixin Lee¹, A. John Haines³ (1.Department of Geography, National Taiwan University, Taiwan, 2.Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Japan, 3.GNS Science, Lower Hutt, New Zealand)

Keywords:Seismic hazard analysis, geodetic and seismic moment rates, regional earthquake forecast model, elasticity-based strain rate model

The present study investigates the potential of seismic and geodetic moment rates in seismic hazard analysis and their integration in developing the regional earthquake model for the whole Taiwan region. For this, the geodetic velocity vectors and the updated historical seismicity records are incorporated. The geodetic velocity vectors are inverted into geodetic strain rates, which are then used to determine geodetic moment rates, while moment magnitudes associated to earthquake events are converted into seismic moment rates. Due to the presence of inelastic components in geodetically measured total strain budget, one of the primary factors contributing to overestimation of earthquake hazards, an empirical correlation factor is introduced to calibrate the moment rate converted from geodetic data with the moment rate of the earthquakes. Toward the final goal, a time-independent earthquake likelihood model is performed to compute probabilities for M_w≧6 earthquakes within 30-years in 0.1*0.1 cells (in degree) across Taiwan by using corrected-geodetic moment rates, truncated G-R law, and the stochastic Poisson process. The emanated results show that (i) the 30-year probability forecasts highlight regions with high seismic hazard, including the locked zone of the Longitudinal Valley fault with gradual decaying toward its southern end and in central Taiwan along the Western Foothill, (ii) the high strain rates and low earthquake occurrence rates in southwestern Taiwan reveal a considerable amount of ongoing inelastic strain deformation in this region, and (iii) various conversion equations and elastic layer parameters (e.g., seismogenic thickness and rigidity) in likelihood models not only impact the seismic hazard outcomes but also provide insights into the heterogeneous tectonics and orogenic processes in Taiwan, driven by plate convergence. Further, with an emphasis on southwestern Taiwan region, several strain rate models based on elasticity-based inversion and/or basis functions are implemented to characterize the seismic-aseismic environment in this area. Discontinuities in the velocity field across creeping faults are also taken into account in some of these models. Collectively, the resulting strain-rate profiles offer profound evidence of aseismic deformation and provide valuable insights into the intricate and dynamic tectonic environment of southwestern Taiwan.