engleski

Estimation of near-surface attenuation in the Northwestern External Dinarides

Ground motion at the site is influenced by source, propagation path, and local site conditions. One of the most important parameters describing ground motion during earthquakes is the Fourier-amplitude spectrum. Spectral parameter kappa is used to describe spectral amplitude decay at high frequencies. Over the last several decades, the researchers are consistent that near site attenuation kappa (site kappa) is affected primarily by site conditions. In this research spectral parameter kappa is estimated from the acceleration amplitude spectrum of shear waves (recordings of local earthquakes with magnitudes higher than 3, epicentral distances less than 150 km, and focal depths less than 30 km from four seismological stations situated in western part of Croatia – Northwestern External Dinarides) from the slope of the high-frequency part where the spectrum starts to decay rapidly to a noise floor. The spatial distribution of individual kappa’s is compared with azimuthal distribution of earthquake epicenters. Also, the obtained results are compared with Vs30 values (from geophysical measurements) and published coda-Q values for each station, as well as with isoseismal maps of stronger events in the investigated area and geological features. These results are significant for extending the knowledge of the attenuation of near-surface crust layers in the Nortwestern External Dinarides and providing additional information on the local earthquake parameters for updating seismic hazard maps of studied area.

Near-surface attenuation, Dinarides, kappa values, coda Q

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