Depth dependence of seismic attenuation in the Messina Strait area

The attenuation structure of the Messina strait area is studied using the single-scattering model of coda wave generation. Data are short-period seismograms belonging to a swarm occurring in the middle of the Messina strait (Italy). The coda-Q appears to be frequency dependent following the empirical law Q = Q0 ƒn, with Q0 and n depending on the coda duration interval. A strong lapse time dependence of Qc (coda-Q) is found. This dependence is interpreted as a depth effect, in the sense that longer codas sample deeper portions of the lithosphere. A simple geometrical model is used to infer from the lapse time dependence in a layered Q-structure of the crust and upper lithosphere. Our results are compared with those obtained in other tectonically active and non-active areas, showing that the inferred Q-structure can be used as a tectonic indicator.