Stochastic source, path and site attenuation parameters and associated variabilities for shallow crustal European earthquakes

Abstract

We have analyzed the recently developed pan-European strong motion database, RESORCE-2012: spectral parameters, such as stress drop (stress parameter, Δσ), anelastic attenuation (Q), near surface attenuation (κ 0) and site amplification have been estimated from observed strong motion recordings. The selected dataset exhibits a bilinear distance-dependent Q model with average κ 0 value 0.0308 s. Strong regional variations in inelastic attenuation were also observed: frequency-independent Q 0 of 1462 and 601 were estimated for Turkish and Italian data respectively. Due to the strong coupling between Q and κ 0, the regional variations in Q have strong impact on the estimation of near surface attenuation κ 0. κ 0 was estimated as 0.0457 and 0.0261 s for Turkey and Italy respectively. Furthermore, a detailed analysis of the variability in estimated κ 0 revealed significant within-station variability. The linear site amplification factors were constrained from residual analysis at each station and site-class type. Using the regional Q 0 model and a site-class specific κ 0, seismic moments (M 0) and source corner frequencies f c were estimated from the site corrected empirical Fourier spectra. Δσ did not exhibit magnitude dependence. The median Δσ value was obtained as 5.75 and 5.65 MPa from inverted and database magnitudes respectively. A comparison of response spectra from the stochastic model (derived herein) with that from (regional) ground motion prediction equations (GMPEs) suggests that the presented seismological parameters can be used to represent the corresponding seismological attributes of the regional GMPEs in a host-to-target adjustment framework. The analysis presented herein can be considered as an update of that undertaken for the previous Euro-Mediterranean strong motion database presented by Edwards and Fah (Geophys J Int 194(2):1190–1202, 2013a).