Effects of site geometry on short-distance spatial coherency in Argostoli, Greece

IMTIAZ ; CORNOU ; BARD ; ZERVA

Type de document
ARTICLE A COMITE DE LECTURE REPERTORIE DANS BDI (ACL)
Langue
anglais
Auteur
IMTIAZ ; CORNOU ; BARD ; ZERVA
Résumé / Abstract
A two-dimensional dense array, deployed at the small and shallow Koutavos-Argostoli valley in Cephalonia, Greece, provided an abundance of data to study the stochastic characteristics of seismic ground motions over very short distances. A set of 46 magnitude 2-5 events at epicentral distances 0-200 km has been selected for the analysis. The lagged coherency of the S-wave dominating seismogram was computed for each station-pair within the array and was averaged over various distance intervals for the whole data set. The results indicate a lack of a clear dependence of the average coherency on the magnitude, back azimuth or site-to-source distance of the event. The most striking result concerns the influence of the site geometry: the coherency is systematically lower for the pairs aligned perpendicular to the axis of the valley (2D) compared to those aligned in the parallel direction. This finding is consistent with the dominance of valley-edge generated surface waves propagating from one edge to the other. The averaged coherency estimates are only weakly represented by the existing parametric models, indicating its strong site dependent nature.
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