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  • 1
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    Reference S-Wave Velocity Profile and Attenuation Models for Ground-Motion Prediction Equations: Application to Japan (2013)
    Seismological Society of America (SSA)
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    Publication Date: 2013-10-01
    Description: Defining the reference rock or soil condition related to ground-motion prediction is an important aspect of seismic-hazard analysis. In a previous study by the authors, a method was proposed to establish a reference rock profile for Switzerland through the comparison of empirical amplification functions with shear-wave velocity profiles at 27 selected sites of the Swiss National Seismic Network. The retrieved velocity profile served as reference for a regional ground-motion prediction equation. However, a lacking piece of information remained: the anelastic attenuation for such a reference profile. Reference attenuation is essential to correctly model and interpret amplification at high frequencies. In the present study we extended our approach to simultaneously model both the reference shear-wave velocity profile and the corresponding attenuation for Japan. We compared site-specific attenuation measurements with quarter-wavelength average velocities at 36 soil and rock sites from the Japanese KiK-net strong-motion network. The selected sites are characterized by a lack of observed resonance phenomena in order to avoid trade-off between amplification and attenuation effects. We establish a parametric model through regression analysis. The resulting model gives us the possibility to estimate anelastic attenuation of a rock site with a given velocity profile and provides the base for host-to-target adjustments of real or modeled ground motion.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 2
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    A Stochastic Ground-Motion Model for Switzerland (2013)
    Seismological Society of America (SSA)
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    Publication Date: 2013-02-07
    Description: We present a stochastic ground-motion model for Switzerland. A model for the far-field Fourier amplitude spectra of earthquakes is first proposed, constrained by ground motions observed from small local and regional earthquakes in addition to macroseismic intensities observed from large damaging events in Switzerland. We then use this model in a stochastic simulation technique to generate predictions of peak ground acceleration and velocity and 5%-damped response pseudo-spectral acceleration. We facilitate the prediction of ground motions from finite-fault sources through the use of the R EFF distance metric and show that magnitude and distance scaling-behavior of events up to M w  7.5 is broadly consistent with Next Generation Attenuation and Japanese models. Ground-motion prediction uncertainty is described in terms of between- and within-event uncertainties through residual analysis of response spectra. Finally, single-station sigma is derived, accounting for the prediction uncertainty at a given site without the ergodic assumption. Consistency of the model is emphasized through its compatibility with other seismic hazard products: the model is referenced to a generic rock profile that was developed by utilizing velocity profiles of the sites of seismic stations and is calibrated at higher magnitudes to the Swiss regional macroseismic intensity prediction model. Furthermore, the model is based on moment magnitudes from the recently developed Earthquake Catalogue of Switzerland 2009 (ECOS09). The well-defined reference for the model means that it can easily be adapted for a site-specific application, for instance, through the use of proxies such as quarter-wavelength velocity and travel-time average shear-wave velocity in the upper 30 m ( V S 30 ).
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 3
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    Empirical evidence of local seismic effects at sites with pronounced topography: a systematic approach (2014)
    Oxford University Press
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    Publication Date: 2014-03-21
    Description: The recent growth of seismic monitoring networks allows for systematic studies of local seismic effects at sites with pronounced topography. We applied a terrain classification method to identify such sites within Swiss and Japanese networks and compiled a data set of high-quality earthquake recordings. As a number of recent studies have found local effects to be directional at sites with strong topographic features, polarization analysis of particle motion was performed and azimuthally dependent resonant frequencies were estimated. The same procedure was also applied for available ambient vibration recordings. Moreover, average residuals with respect to ground motion prediction models for a reference bedrock were calculated to estimate the average amplification or deamplification for each station. On one hand, observed amplifications are found to be tightly linked with ground motion directionality as estimated by polarization analysis for both earthquake and ambient vibration recordings. On the other hand, we found no clear relation between local topographic features and observed amplification, so the local subsurface properties (i.e. shear wave velocity structure) seem to play the key role and not the geometry itself.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 4
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    Characterizing the Vertical-to-Horizontal Ratio of Ground Motion at Soft-Sediment Sites (2012)
    Seismological Society of America (SSA)
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    Publication Date: 2012-12-01
    Description: A predictive equation to obtain the vertical-to-horizontal ratio (V/H) of ground motion for rock sites has been established in a previous article. The method was based on the comparison between V/H of Fourier and response spectra of earthquakes with the quarter-wavelength average velocity at discrete frequencies. We extend this approach to account for resonance phenomena at soft-sediment sites. In order to do so, a new parameter is defined and included in the comparison with the V/H spectra. The new parameter is directly derived from the quarter-wavelength velocity and represents the frequency-dependent seismic impedance contrast at the site. We show that extending the correlation in this three-dimensional space is beneficial to reconstruct V/H of the 5%-damped response spectra at soft-sediment sites ( V S 30 〈800 m/s) for which a shear-wave velocity profile is available. In this study we analyze 220 sites of the Japanese KiK-net strong-motion network. These sites were selected from the entire network through comparison of the fundamental frequencies estimated from the recordings and by indirect modeling methods. From the analysis, two types of predictive equations are then established, the first based on frequency-dependent and the second on frequency-independent correlations. These can subsequently be used to reconstruct the V/H spectrum at any site with a known shear-wave velocity profile. For both equations, uncertainties of the V/H models are provided, and a sensitivity study to magnitude–distance dependence is presented. Finally, we show an example of the application of the model at four selected soft-sediment sites of the Swiss Seismic Network.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 5
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    Measurements of stress parameter and site attenuation from recordings of moderate to large earthquakes in Europe and the Middle East (2013)
    Oxford University Press
    Details
    Publication Date: 2013-07-05
    Description: We analyse the raw, unfiltered acceleration time-series strong-motion data used for the European Strong Motion Database. After selecting high-quality recordings, suitable for Fourier analysis, we estimate crustal and site attenuation properties, Q 0 and 0 , respectively, using two methods: a broad-band spectral modelling approach and a high-frequency linear fit. We find 0 varies strongly, from negligible to 0  = 0.09 s, with an average of 0  = 0.032 s or 0  = 0.033 s depending on the method employed. This is consistent with the wide variety of recording-site conditions from hard-rock to very-soft soil. Using the attenuation model, we then proceed to determine site-class amplification, seismic moments and 2 stress parameters for several events with M w values between 5 and 7.6. Site amplification is shown to vary strongly within a single site-class, although average amplification is consistent with resonance expected at soft-soil sites and theoretical crustal amplification at hard-rock sites. We show that seismic moments determined from Fourier spectra are consistent with database M w values from moment tensor analysis, and that the resulting stress parameters are independent of magnitude or depth. Finally, we show that using the results of our analyses, along with the R eff distance metric to account for the geometry of the finite fault, we can predict pseudospectral acceleration (peak ground acceleration to 10 s) of the Izmit 1999 ( M w  7.5–7.6) event using a point-source stochastic simulation.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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