The group velocity in the longer period was generally sensitive to the deeper velocity structure and exhibited significant spatial variation.
For the deeper velocity structure, we used a regional velocity model for central Japan based on Ikami et al. (1986) and Kato et al. (2007).
For instance, the relationship between (V_{{{text{s}}30}}) and deeper velocity structure is not identical in the Los Angeles basin, Japanese coastal plains, or intra-mountain basins in the Alps or the Apennines; therefore, the associated long- or short-period effects may differ.
In Fig. 6, we show matching of EHVRs at EHM012, a convergence path for 200 generations, and the shallow and deep S-wave velocity structures obtained, as an example.
Satoh et al. (2001a, b) carried out array microtremor measurements in Sendai and nearby cities to obtain the deep S-wave velocity structures inside the Sendai basin, and the earthquake ground motions were also measured at the center of each array.
Thus, we adopted the local S-wave velocity structures at 14 deep boreholes and SIT003 for our model construction.
The ellipticities of fundamental mode of Rayleigh waves at all stations have two peaks which are caused by the underground velocity structures of shallow layers, and deep layers, respectively.
In addition, limited numbers of VSP measurements at deep boreholes (deeper than 1 km) have revealed very accurate in situ seismic velocity structures (Yamamizu1996,2004).
The f min is determined in consideration of the depth of underground velocity structures from surface to bottom, e.g, it may be not deep enough to explain peak at low frequency or long period.
c Velocity structures used in this study.
