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

[SGD01-06] Analysis of Long-Term Slip Rates of Active Faults and Regional Surface Deformation Rates Using a Finite Element Kinematic Model: Application to the Taiwan Orogenic Belt

*Yi Jui Lee¹, Jyr-Ching Hu² (1.SINOTECH engineering consultants, INC., 2.Department of Geosciences, National Taiwan University)

Keywords:finite element kinematic model, active fault slip rate, distributed deformation rate

The National Seismic Hazard Model (NSHM) of the United States was updated in 2023. For the deformation model, five models were used in the western United States: Geologic (weight 0.26), Shen-Bird (weight 0.32), Zeng (weight 0.32), Pollitz (weight 0.08), and Evans (weight 0.02). Among them, the Shen-Bird model, which has a higher weight, is the Neokinema model used in this study. The inputs to Neokinema model include the relative motion of plates (as boundary conditions), the GNSS horizontal velocity field related to tectonic movement (used for interpolation at each grid point), and the actual principal stress direction data (as a constraint on the principal strain direction). Long-term slip rates are analyzed from the velocity gradient across the modeled faults. In addition, Neokinema model can also calculate the regional deformation rate from the velocity differences at nodes of the same triangular mesh.
Taking the Taiwan Orogenic Belt as an example, this study obtained the strike-slip and dip-slip rates of Taiwan's 36 active faults, as well as the distributed permanent strain rate for each finite element grid from Neokinema modeling. The distributed permanent strain rates showed relatively high values at northeast, southwest, and southeast areas of Taiwan Island. However, there are no modeled fault in these areas. We suggest that these regions require further investigation to see if there are undiscovered faults.
Japan is also located in a plate boundary seismic zone and has accumulated relevant research over many years. As long as fault survey data (including fault traces, fault geometries, and geological long-term slip rates), GNSS velocity field data, and principal stress direction data are collected, this research method can also theoretically be applied to assess the slip rates of all active faults in Japan.