Estimation of group velocity of Green’s function in the sedimentary basin from crosscorrelation of ambient noise around

The Fujikawa-kako fault zone in central Japan is one of the most active faults. For the strong motion prediction, it is necessary to construct S-wave velocity structure model of sedimentary layers around the fault zone. Several 3D velocity structure models has been proposed in the area. In order to choose the appropriate velocity structure model, we used seismic interferometry to retrieve Green’s functions and estimated group velocity of Rayleigh wave from the crosscorrelation function. The crosscorrelation functions in the vertical component propagate with the velocity of 1 km/s. Group velocity of the Green’s function was estimated using Frequency-Time Analysis. We observed clear group velocity between the stations pairs across the fault. The estimated velocity was slower than the theoretical velocity of the existing model. There is possibility to use group velocity for the improvement of the existing S-wave velocity structure model.