Coda-Q and its lapse time dependence analysis in the interaction zone of the Dinarides, the Alps and the Pannonian basin

• We analysed attenuation of coda waves using the single backscattering model.
• We analysed frequency dependence of coda-Q for different lapse times.
• Obtained Q0 and n, from the form Qc(f) = Q0fn, describe very heterogeneous area.
• Q0 increases and n decreases with lapse time.
• We found good correlation between n and the Moho depth for lapse times 50–70 s.

The single backscattering model was used to estimate total attenuation of coda waves (Qc) of local earthquakes recorded on eight seismological stations in the complex area of the western continental Croatia. We estimated Q0 and n, parameters of the frequency dependent coda-Q using the relation Qc = Q0fn. Lapse time dependence of these parameters was studied using a constant 30 s long time window that was slid along the coda of seismograms. Obtained Qc were distributed into classes according to their lapse time, tL. For tL = 20–50 s we estimated Q0 = 45–184 and n = 0.49–0.94, and for tL = 60–100 s we obtained Q0 = 119–316 and n = 0.37–0.82. There is a tendency of decrease of parameter n with increasing Q0, and vice versa. The rates of change of both Q0 and n seem to decrease for lapse times larger than 50–80 s, indicating an alteration in rock properties controlling coda attenuation at depths of about 100–160 km. A very good correlation was found between the frequency dependence parameter n and the Moho depths for lapse times of 50, 60 and 70 s.