2019 Volume 72 Pages 49-67
In this study, in order to examine the applicability of phase velocity estimation method using Green's functions with a common virtual source by seismic interferometry, we conducted continuous seismic observation at 16 points in Wakasa Bay region, and estimated the phase velocity by using both the positive side of the cross correlation function having large amplitude and the negative side of the cross correlation function having small amplitude, and compared the both results. In a case where the signal of the cross-correlation function on the side corresponding to the propagation direction from the common virtual source to the observation points is clear, it is possible to estimate the phase velocity stably from the Green's functions with a common virtual source, and the result is almost same as the phase velocity obtained by the natural earthquake records. On the other hand, in a case where the signal of the cross-correlation function on the side corresponding to the propagation direction from the common virtual source to the observation points is unclear, the phase velocity can not be estimated. However, it was found that the phase velocity can be estimated satisfactorily by using the cross correlation function whose sign of delay time is opposite as the Green’s functions with the common virtual source. Furthermore, when the Green’s functions become asymmetric shape as in this study, it was found that we could estimate the phase velocity by placing a seismic observation point in the direction where the signal becomes strong.
