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A ground-motion prediction equation (GMPE) specific to rock and stiffsoil sites is derived using seismic motion recorded on high V S30 sites in Japan. This GMPE applies to events with 4:5 ≤ M w ≤ 6:9 and V S30 ranging from 500 to 1500 m=s (stiff-soil to rock sites). The empirical site coefficients obtained and the comparison with the simulated site functions show that seismic motion on rock and stiff-soil sites does not depend only on V S30 , but also on the high-frequency attenuation site properties (κ 0 ). The effects of the site-specific κ 0 on site amplification are analyzed using stochastic simulations, with the need to take into account both of these parameters for rock-site adjustments. Adding the site-specific κ 0 into the GMPEs thus appears to be essential in future work. The rock-site stochastic ground-motion simulations show that the sitespecific κ 0 controls the frequency corresponding to the maximum response spectral acceleration (f amp 1). This observation is used to link the peak of the response spectral shape to κ 0 in this specific Japanese dataset and then to add the effects of high-frequency attenuation into the previous GMPE from the peak ground acceleration and up to periods of 0.2 s. The inclusion of κ 0 allows the observed bias to be corrected for the intraevent residuals and thus reduces sigma. However, this κ 0 determination is limited to a minimum number of rock-site records with M w ≥ 4:5 and to distances of less than 50 km.

A key component in seismic hazard assessment is the estimation of ground motion for hard rock sites, either for applications to installations built on this site category, or as an input motion for site response computation. Empirical ground motion prediction equations (GMPEs) are the traditional basis for estimating ground motion while V S30 is the basis to account for site conditions. As current GMPEs are poorly constrained for V S30 larger than 1000 m/s, the presently used approach for estimating hazard on hard rock sites consists of ''host-to-target'' adjustment techniques based on V S30 and j 0 values. The present study investigates alternative methods on the basis of a KiK-net dataset corresponding to stiff and rocky sites with 500 \ V S30 \ 1350 m/s. The existence of sensor pairs (one at the surface and one in depth) and the availability of P-and S-wave velocity profiles allow deriving two ''virtual'' datasets associated to outcropping hard rock sites with V S in the range [1000, 3000] m/s with two independent corrections: 1/down-hole recordings modified from withinThe following softwares are employed in this study: 1) the one written by J.-C. Gariel and P.-Y.Bard of the 1D reflectivity approach (Kennett 1974); 2) the site_amp v.5.6 program package provided by Dave Boore (U.S. Geological Survey); and the pikwin software developed by Perron et al. (2017). DOI 10.1007/s10518-017-0142-6 motion to outcropping motion with a depth correction factor, 2/surface recordings deconvolved from their specific site response derived through 1D simulation. GMPEs with simple functional forms are then developed, including a V S30 site term. They lead to consistent and robust hard-rock motion estimates, which prove to be significantly lower than host-to-target adjustment predictions. The difference can reach a factor up to 3-4 beyond 5 Hz for very hard-rock, but decreases for decreasing frequency until vanishing below 2 Hz. Electronic supplementary materialBull Earthquake Eng