Near-Fault Broadband Ground-Motion Simulations of the 2016 Meinong, Taiwan, Earthquake

Near-fault broadband ground-motion simulations of the 2016 M w 6.4 Meinong, Taiwan, earthquake are carried out using the stochastic finite-fault modeling method with the frequency-dependent S-wave radiation pattern. We simulate broadband ground motions that recorded large velocity pulses, with dominant periods of about 2 s, in both east-west (EW) and north-south (NS) components in the forward rupture direction using two hybrid approaches: a hybrid stochastic-analytical approach and a hybrid stochastic-deterministic approach. We also simulate broadband ground motions that did not record large-velocity pulses using a pure stochastic method. The simulated ground motions using the hybrid stochastic-analytical approach reproduce the observed large EW- and NS-component velocity pulses, and the simulated spectral accelerations show good overall fitting with the observation data for periods shorter than 3 s. However, the EW and NS velocity amplitudes are underestimated because of the limited availability of velocity structure models for western Taiwan even though the simulated ground motions using the hybrid stochastic-deterministic approach reproduce velocity phases very similar to the observation data. The peak ground accelerations (PGAs) and spectral acceleration values of the simulated ground motions obtained using the pure stochastic method fit well with the observation data. By comparing the ground-motion prediction equations developed for shallow crustal earthquakes in Taiwan with the observed and simulated PGAs and spectral accelerations, we find that the prediction models without a directivity correction term underestimate spectral accelerations for periods around 1 s and longer for stations that recorded large velocity pulses near the main rupture area. Finally, we simulate strong ground motions at two collapsed building sites in the city of Tainan where ground motions were not observed.