Toward Reliable Characterization of Sites With Pronounced Topography and Related Effects on Ground Motion

Here we present first results of a joint effort undertaken in ongoing European project NERA -JRA1, which aims at establishing scientifically solid and practically acceptable propositions to incorporate surface topography effects in seismic hazard estimates. We assembled a dataset of both ambient vibration and earthquake recordings acquired at 40 European sites with pronounced topography. It comprises a wide variety of sites including populated hills and even extreme cases of unstable rock slopes in Alpine regions. Results of the polarisation analysis for the two sites presented here show the peculiarity of the topographic site effects

Statistical signal processing workshop (SPP)

In this paper, we present MUSIQUE, an algorithm designed to analyze seismic signals recorded by arrays of three-component seismic sensors. Using the original MUSIC algorithm [1], azimuth and slowness (or velocity) of incident waves are estimated. The quaternion-MUSIC algorithm [2, 3] is then used to characterize the polarization properties of the waves. In this way, Love and Rayleigh waves are distinguished and their respective properties retrieved. This allows the characterization of the seismic wave field and the soil structure underneath the seismic array, which are important parameters for the estimation of seismic hazards

Méthode simplifiée pour estimer la performance sismique de petits barrages en remblai homogènes

International Symposium Qualification of Dynamic Analyses of Dams and their Equipment and of Probabilistic Assessment of Seismic Hazard in Europe, Saint-Malo, FRA, 31-/08/2016 - 02/09/2016International audienceWe propose a new simplified method for assessing the seismic performance of homogeneous small earth dams (height < 20 m) founded on bedrock. Dynamic decoupled calculations were performed on seven accelerograms applied to 33 structural and geotechnical configurations. We studied the influence of embankment geometries and mechanical properties on the prediction of earthquake-induced permanent displacements estimated using Newmark analyses. This paper also discuss the relevance of this model comparing it with existing simplified models and with post-seismic field observations. A regression analysis based on easily accessible parameters characterizing the structure (yield coefficient and initial fundamental period) and the ground motion (peak ground acceleration and Arias intensity) was used to provide a pseudo-empirical predictive equation to carry out rapid preliminary seismic performance assessments

The INTERPACIFIC project: a cooperative exercise for assessing reliability and accuracy of seismic methods

In recent years, the use of surface wave tests for seismic site characterization has expanded rapidly in the field of applied seismology and earthquake engineering. Indeed these methods are cost and time effective with respect to the invasive ones, which require the use of boreholes. For surface wave methods, difficult and onerous interpretation and inversion processes are needed to derive a reliable S-wave velocity (VS) profile. At the same time, the availability of affordable seismic equipment and “black-box” processing software has led to a wide diffusion of surface wave methods among inexperienced analysts. The combination of the aforementioned factors induces in the final user (i.e., the engineer or the seismologist who require the shear wave velocity model) a lack of confidence in results obtained from surface wave testing. On the other hand, borehole seismic methods are often considered a more reliable option since they provide a highly resolved VS profile with a simpler interpretation process. Nonetheless, some previous comparisons between repeated realizations of borehole methods have shown controversial results and an unexpected lack of repeatability. A systematic assessment of the performance of different seismic methods is thus crucial. Furthermore, it is also necessary to develop firm standards and guidelines for execution and interpretation of surface wave tests. Fixing a standard practice for surface-wave methods is a very challenging task because the measurements can be performed with a wide variety of experimental configurations and interpreted with an even larger spectrum of signal analysis and inversion techniques

Inversion of surface wave dispersion at European strong motion sites using a multi-model parameterization and an information-theoretic approach

International audienceWithin the scope of the EC-projects NERIES and ITSAK-GR we have applied a procedure able to combine a multi-model space parameterization and an information theoretic approach in analysis of dispersion curve inversion. In detail we considered the dispersion curve assessed at 14 strong motion European sites. At each site we investigated the model space through four different parameterization groups within the wavelength range estimated by actual dispersion curves. In order to explore the influence of model space we increased progressively the number of layers for each parameterization. We therefore addressed the model evaluation among a set of competing models obtained by inversion following the corrected Akaike's Information Criterion (AICc). By using such information-theoretic approach, we found an acceptable agreement between the inverted shear-velocity profiles of the best models and the available borehole results

Inversion of surface wave dispersion at European strong motion sites using a multi-model parameterization and an information-theoretic approach

International audienceWithin the scope of the EC-projects NERIES and ITSAK-GR we have applied a procedure able to combine a multi-model space parameterization and an information theoretic approach in analysis of dispersion curve inversion. In detail we considered the dispersion curve assessed at 14 strong motion European sites. At each site we investigated the model space through four different parameterization groups within the wavelength range estimated by actual dispersion curves. In order to explore the influence of model space we increased progressively the number of layers for each parameterization. We therefore addressed the model evaluation among a set of competing models obtained by inversion following the corrected Akaike's Information Criterion (AICc). By using such information-theoretic approach, we found an acceptable agreement between the inverted shear-velocity profiles of the best models and the available borehole results

Earthquake engineering in Europe

A series of investigations has been carried out over the last decade in Europe aimed at deriving quantitative information on site amplification from non-invasive techniques, based principally on surface wave interpretations of ambient noise measurements. The present paper focuses on their key outcomes regarding three main topics. First, methodological, hardware and software developments focusing on the acquisition and the processing of both single point and array microtremor measurements, led to an efficient tool with in situ control and processing, giving rise to robust and reproducible results. A special attention has been devoted to the derivation and use of the Rayleigh wave ellipticity. Second, the reliability of these new tools has been assessed through a thorough comparison with borehole measurements for a representative - though limited - set of sites located in Southern Europe, spanning from stiff to soft, and shallow to thick. Finally, correlations between the site parameters available from such non-invasive techniques, and the actual site amplification factors as measured with standard techniques, are derived from a comprehensive analysis of the Japanese KIKNET data. This allows to propose alternative, simple site characterization providing an improved variance reduction compared with the "classical" VS30 classification. While these results could pave the road for the next generation of building codes, they can also be used now for regulatory site classification and microzonation studies, in view of improved mapping and estimation of site amplification factors, and for the characterization of existing strong motion sites