Characteristics of near-fault velocity pulses in the strongest pulse orientation

In order to explore the characteristic difference of velocity pulse between the strongest velocity pulse component and those of the vertical fault or parallel fault component, the strongest pulse orientation components were extracted from 236 groups of near-fault ground motion velocity pulse records of the strong ground motion database NGA-West2 by using the multi-components velocity pulse identification method. Then, relationships of the pulse amplitude and the period with magnitude and fault distance were also analyzed by regression. Finally, characteristics of pulses in the strongest pulse orientation and in vertical or parallel fault orientation were compared. The following conclusions can be made: When the fault distance is less than 30 km, the predicted value of the peak ground velocity in the strongest pulse orientation is larger than that in the vertical or parallel fault orientation. However, with the increase of the fault distance, the difference of the peak velocities in the two orientations can be neglected. The pulse period is smaller in the strongest pulse orientation than in the vertical or parallel fault orientation for records with magnitude M_W smaller than 7.5, whereas when magnitude M_W is greater than 7.5, the difference of the pulse period between the two orientations can be ignored.