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

Abstract

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 30s 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=20–50s we estimated Q0=45–184 and n=0.49–0.94, and for tL=60–100s 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 50–80s, indicating an alteration in rock properties controlling coda attenuation at depths of about 100–160km. A very good correlation was found between the frequency dependence parameter n and the Moho depths for lapse times of 50, 60 and 70s.