Rock and Stiff-Soil Site Amplification: Dependency on VS30 and Kappa ( 0)

Abstract

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.

Taxonomy of : A Review of Definitions and Estimation Approaches Targeted to Applications

“…Indeed, the Probabilistic Seismic Hazard Analysis for Swiss Nuclear Power Plant Sites (PEGASOS) Refinement Project (Biro and Renault, 2012) showed that, for hard rock, the V S30 and κ 0 corrections can lead to differences up to a factor of 3 in the high-frequency part of the response spectrum. Given the significance of κ 0 , in the past year attempts were also made to explicitly include it in the functional form of GMPEs (Laurendeau et al, 2013), an idea that actually originated as early as Anderson et al (1996).…”

“…Ktenidou et al (2013) show the effect of exceeding the available frequency range either as constrained by the signal-to-noise ratio (this should constrain f 2 ) or by the corner frequency (this should constrain f 1 ) in the estimation of κ 0 , but the problem may begin even before this stage. For instance, Laurendeau et al (2013) point out that, in choosing f 2 for their κ AS estimation, Van Houtte et al (2011) neglected to account for a low-pass filter present in all KiK-net instruments, which may have affected κ r . Data should preferably only be used after correcting for instrument response or, at least, checking the maximum usable frequency up to which response is flat.…”

“…4;Van Houtte et al, 2013). Today we are more aware of the importance of understanding ground motion at high frequencies, even above 30 or 50 Hz; e.g., Silva and Darragh (2012), and Laurendeau et al (2013) show the effect of κ at frequencies above 50 Hz. We also have the means to record and acquire data at higher frequencies.…”

Hard-Site 0 (Kappa) Calculations for Christchurch, New Zealand, and Comparison with Local Ground-Motion Prediction Models

“…For some ground-motion simulation codes (e.g., Boore, 2003;Motazedian and Atkinson, 2005), κ 0 is an input parameter to model the high-frequency shape of the simulated spectra, by controlling the rate of decay of an exponential low-pass filter applied across the entire frequency band. In conjunction with V S30 (the time-averaged shear-wave velocity in the first 30 m below ground surface), the κ 0 parameter has recently been used to more accurately model rock-site amplification functions and has been implemented as a predictor variable in an empirical ground-motion prediction equation (GMPE) for rock sites (Laurendeau et al, 2013). For the purposes of site-specific ground-motion prediction, κ 0 is used as a GMPE adjustment parameter in the host-to-target method of Campbell (2003), accounting for regional differences in rock-site attenuation between the host and target regions (Cotton et al, 2006;Douglas et al, 2006;Van Houtte et al, 2011).…”

Squeezing Kappa (κ) Out of the Transportable Array: A Strategy for Using Bandlimited Data in Regions of Sparse Seismicity

“…It is used as a site parameter for describing high-frequency motion in various applications, including the simulation of ground motion and the creation and adjustment of groundmotion prediction equations (GMPEs) from one region to another (Biro and Renault, 2012). In the latter context, κ 0 (as opposed to V S ) can be the dominant factor in characterizing the response of rock sites (Laurendeau et al, 2013), particularly in regions of low seismicity and stable continental regions.…”