Application of stochastic finite-fault method to marine earthquake : 2021 Fukushima earthquake in Japan

The stochastic finite-fault method is widely used to the broadband ground motion simulation for seismic engineering with the characteristics of not relying on fine underground wave velocity structure, less undetermined parameter and fast calculation speed. In this study, we take the 2011 Fukushima earthquake in Japan sea area as a study case, and adapt the stochastic finite-fault approach to simulate KiK-net borehole station. The study showed the results simulation by stochastic finite-fault method are small for stations near the fault but high for stations located on the land boundary. However, the simulated pseudo-acceleration response spectrum (PSA) has a residual close to 0 in the frequency ranging from 0.1 to 10 Hz, indicating that the method is effective in an average sense for the land ground motion simulation in marine earthquake. In addition, the simulation results were also compared with the Ground Motion Prediction Equation (GMPE) of BC-Hydro subduction zone in terms of ground motion characteristics, such as PSA and PGA. It is found that the predicted values by the BC-Hydro GMPE are significantly lower than observed values and the difference trend between them is basically a constant at high frequencies, indicating that the global average stress drop adopted in the GMPE is small when it is applied to the Fukushima earthquake, Japan. Overall, this study provides a reference to the application of stochastic finite-fault method in marine earthquake and to the development of corresponding ground motion prediction equations.