Analysis of near-fault velocity pulses in the Chi-Chi earthquake

This paper preliminary analyzed the causes and characteristics of the near-fault velocity pulse, including the directivity effect, fling-step effect, and hanging wall effect. The influence of fault rupture direction and slip size on the peak ground velocity was analyzed using the pulse records of 27 near-fault stations in the Chi-Chi earthquake. The distribution of velocity pulses was analyzed with least squares method. The velocity pulses larger than 50 cm/s were mainly concentrated in the near-fault region with a fault distance of 10 km. The statistical analysis of the three-component average velocity response spectrum in different regions shows that the near-fault pulse-like ground motion has a large characteristic period and spectral value, especially the horizontal component perpendicular to the fault strike. This is basically consistent with the characteristics of the radiation effect of the shear dislocation. In view of the phenomenon that near-fault geological disasters were frequently caused by the pulse-like earthquake, we analyzed the resonance effect of velocity pulse on the slope rock masses. This study of near-fault velocity pulse may provide some significant references for earthquake prevention and disaster reduction, earthquake early warning and seismic damage assessment.