Earthquake Ground Motion in the Mygdonian Basin, Greece: The E2VP Verification and Validation of 3D Numerical Simulation up to 4 Hz

Abstract

International audiencen a low‐seismicity context, the use of numerical simulations becomes essential due to the lack of representative earthquakes for empirical approaches. The goals of the EUROSEISTEST Verification and Validation Project (E2VP) are to provide (1) a quantitative analysis of accuracy of the current, most advanced numerical methods applied to realistic 3D models of sedimentary basins (verification) and (2) a quantitative comparison of the recorded ground motions with their numerical predictions (validation). The target is the EUROSEISTEST site located within the Mygdonian basin, Greece. The site is instrumented with surface and borehole accelerometers, and a 3D model of the medium is available. The simulations are performed up to 4 Hz, beyond the 0.7 Hz fundamental frequency, thus covering a frequency range at which ground motion undergoes significant amplification. The discrete representation of material heterogeneities, the attenuation model, the approximation of the free surface, and nonreflecting boundaries are identified as the main sources of differences among the numerical predictions. The predictions well reproduce some, but not all, features of the actual site effect. The differences between real and predicted ground motions have multiple origins: the accuracy of source parameters (location, hypocentral depth, and focal mechanism), the uncertainties in the description of the geological medium (damping, internal sediment layering structure, and shape of the sediment‐basement interface). Overall, the agreement reached among synthetics up to 4 Hz despite the complexity of the basin model, with code‐to‐code differences much smaller than predictions‐to‐observations differences, makes it possible to include the numerical simulations in site‐specific analysis in the 3D linear case and low‐to‐intermediate frequency range

Sensitivity analysis of synthetic seismograms in sedimentary basin with respect to uncertain seismological parameters

“…Our implementation is being widely used for computing seismic wave propagation in complex geological media (De Martin et al 2013;Matsushima et al 2014;Chaljub et al 2015;Maufroy et al 2015). An animation of wave propagation performed for this study is available at http://efispec.free.fr/videos/e2vp2.shaheenII.mp4.…”

“…To foster the use of linear 3D numerical simulations in practical prediction, E2VP aimed at (a) evaluating the accuracy of the most-advanced numerical methods when applied to realistic 3D models and (b) providing an objective, quantitative comparison between recorded earthquake ground motions and their numerical predictions. So far, these two objectives (a) and (b) have been thoroughly tackled; they are published in Chaljub et al (2015) and Maufroy et al (2015). As a continuation of the E2V project, the sourcerelated variability of the site is presented by Maufroy et al 2017; and this study investigates the variability and sensitivity of earthquake ground motions associated with the epistemic uncertainties of the E2VP model.…”

Analysis of rotation sensor data from the SINAPS@ Kefalonia (Greece) post-seismic experiment—link to surface geology and wavefield characteristics

“…institut-seism.fr/projets/sinaps/, Berge-Thierry et al 2016). A permanent accelerometric vertical network within the Koutavos basin, known as "Argonet, " has been installed with the long-term objective to perform the validation of three-dimensional, nonlinear computer codes (the notion of code validation being the quantitative comparison of the recorded ground motions with their numerical predictions, see, e.g., Maufroy et al 2015).…”

Surface wave group velocity in the Osaka sedimentary basin, Japan, estimated using ambient noise cross-correlation functions

“…A traditional method of validating a model is numerical simulation of ground motion excited by small to large earthquakes (e.g., Aagaard et al 2008;Aoi et al 2008;Iwaki and Iwata 2010;Dhakal and Yamanaka 2013; Maufroy et al 2015;Asano et al 2016b;Guo et al 2016;Taborda et al 2016). For modeling a real earthquake, the source model and wave propagation outside the target area should be examined.…”