High frequency attenuation k parameter and Qs 3D model for south-eastern Alps and north-western Dinarides

We estimated the spectral decay parameter k using waveforms produced by small-to-moderate earthquakes in the time period 1994-2011 in NE Italy and western Slovenia. We reconstructed the 3D distribution of the frequency independent part of the S waves' quality factor, Q(S), by using k values and S waves velocity V-S values as input. The Q(S) model presented marked lateral and depth variations with a zone of low Q(S) in the Kobarid area (western Slovenia). Considering these data together with available 31) distribution of V-P, V-P/V-S and shear modulus, we hypothesize that this is a highly fractured area permeated by fluids with variable pore pressure. At depths of 6-9 km, both in the central and in the western part of the area under study, two regions are characterized by significant lateral and in-depth Q(S) contrasts. We interpreted these results in terms of amount of crack density and geological units.