Q factor estimation from the aftershock sequence of the 13 May 1995 Kozani earthquake

Abstract

The single isotropic scattering model has been applied for the estimation of coda Q values for a number of small aftershocks of the Kozani-Grevena 1995 earthquake. The events were recorded by the telemetric network of the Geodynamic Institute of National Observatory of Athens. Coda Q c estimations were made for three frequency bands centered at 1 Hz, 2 Hz, and 4 Hz, and for lapse time windows 2 t s to 100 sec every 20 sec. The coda Q values obtained show a clear dependence of the form Q c = Q 0 f n , while Q 0 and n depend on the lapse time window. Q 0 was found to range from 50 to 160, and increases as lapse time increases. On the contrary, n decreases as lapse time increases and its values range from 1.02 to 0.76 with a tendency to be stable over 80 sec. This lapse time dependence is interpreted as being due to a depth-dependent attenuation. The temporal variation of Q c was also examined within a month time period, but although the results show a tendency of temporal variation at of Q c at 1 Hz, the case needs more investigation.