Statistical Analysis of Characteristic Parameters and Probability Distribution of Near-Fault Velocity Pulses—A Case Study on the 1999 Mw 7.6 Chi-Chi Earthquake

Abstract The 1999 Mw 7.6 Chi-Chi earthquake in the Taiwan region generated valuable ground motions, providing an opportunity for studying the characteristic parameters and distribution of near-fault velocity pulses. Using the finite-difference method, we built a source model, simulated the 1999 Mw 7.6 Chi-Chi earthquake ground motions, and obtained synthetic velocity waveforms consistent with the observed waveforms. On this basis, we analyzed the distribution of velocity pulses in the near-fault region and compared it with the pulse probability distribution (PPD) curve of the near-fault velocity pulse. We found that the complex rupture process of the Mw 7.6 Chi-Chi earthquake resulted in velocity pulses still being recorded in Miaoli and Xinzhu. In addition, we analyzed the relationship between pulse period, pulse peak, and fault distance. The pulse peak indicates a clear attenuation trend with increasing fault distance (Rrup) and no statistical relationship between the pulse period and Rrup. More velocity pulses in normal-fault components reveal the reverse fault of the Chi-Chi earthquake. Finally, structures with natural periods within the 1–7 s are more susceptible to resonance from near-fault velocity pulses, and it is necessary to take appropriate seismic measures. This study lays the foundation for a deeper understanding of the ground motion and pulse characteristics caused by earthquakes and contributes to sustained efforts in seismic hazard assessment.