## 5 Discussion  
In this paper, we calculated the strong ground motions in southwestern Japan for a hypothesized Tonankai earthquake and the whole rupture scenario along the Nankai Trough using a non-uniform slip model and a statistical Green's function derived from observed ground motions. The resultant synthetics were compared with well-established GMPE predictions and seismic intensity estimates from the historical damage records as well as the predicted maps made by CDMC for disaster preparation activities inside the Japanese government. As long as the stochastic nature of the source, path, and site effects is properly represented in the elementary source and the scaling relationships from the elementary source to the hypothesized mega-thrust events are properly expressed, the resultant synthetics would be quantitatively predicted. The major drawback of the current approach, which is based on the observed strong motions, is its inability of prediction at an arbitrary point; we need to deploy a seismic station at a target site if it is not close to any of the stations that we used. There are several ways to skip that kind of time-consuming effort in order to obtain a site-specific site amplification factor. One way is to use observed microtromers at the site and apply the recently proposed double correction method on the horizontal-to-vertical spectral ratio (HVSR) of microtromers [37]. In the double correction method, first, the HVSR of microtromers should be converted to the HVSR of earthquakes using an empirically determined spectral ratio. Then, the transformed HVSR of earthquakes should be converted to the horizontal site amplification factor using an empirically determined average vertical amplification correction factor. The validity of the latter has also been reported by [PERSON] et al. [38]. Another viable way is to use ground response analysis (GRA) to calculate the site-specific site amplification factor through 1D/2D/3D numerical modeling of the underground structure around the site. However, we need to have a good velocity structure from the surface down to the seismological bedrock where we need not consider any site effects, which means the layer whose S-wave velocity should be 3 km/s or higher. It is not easy to delineate a reliable velocity structure of that scale at an arbitrary point without a significant investment. Recently, we have proposed an innovative way to interpolate site amplification factors in between the strong motion stations using 1D GRA based on the detailed velocity profiles with the spatial resolution of 250 m in the Kanto and Tokai regions [39]. After synthetic ground motions were obtained, we performed the damage prediction of wooden houses, steel structures, and RC structures using the building damage prediction model that relies on the nonlinear structural responses with multiple sub-models with  
Figure 24: The distribution of the numbers of damaged buildings per unit area by CDMC [32]. different yield capacities. As a result, the possibility of heavy building damage or collapse was identified in the coastal regions close to the fault and regions with relatively thick, soft sediments, such as areas inside alluvial plains. These dangerous cities are found mainly around near-fault regions such as Kochi, Tokushima, and Wakayama Prefecture, and areas around the Ise Bay. The damage ratio by structure type is highest in steel structures, followed by wooden houses, and then RC structures. The overall geographical pictures of our damage prediction are similar to the previous simulations by the government; however, we found that the prediction by CDMC [32] for the whole rupture scenario (Figure 24) seems to be overestimated by several reasons, although we have not translated yet our damage ratio prediction into the number of damaged buildings per unit area as conducted by CDMC. What are the possible sources of the difference between our prediction and theirs?