In order to simulate the dynamic response of a homogeneous saturated sand layer in FLAC2D, the following confusions are arising:

Before running the model with Rayleigh + Hysteretic damping, the model is run under undamped condition. In undamped condition, a Sxy correction is needed by matching the input velocity history with computed velocity history. Now, the problem is that the peaks can be matched, but the computed time history gets shifted, so how to match the position of the peaks in time axis. Another issue is shall I use the corrected Sxy in the damped analysis with Rayleigh + Hysteretic damping? or Sxy is just corrected in undamped condition to pick the central frequency of power spectrum so that Rayleigh damping can be defined in the damped analysis.