Nr.2 - ALPA - Albanian Papers

Dushi & Lamedecrease with lapse time at different frequencies.In general cases, Q increases with frequency,following the relation:Here,, is the quality factor at the referencefrequency (generally = 1 Hz) and is thefrequency parameter close to 1, varying fromregion to region depending on theheterogeneities of the medium. Hence, theseismic data are first band-pass filtered in orderto calculate the attenuation. We have taken inconsideration the Coda of S-Waves, as dominantphases at local and regional distances recordedfrom ASN. The amplitude of S-Coda at lapse timet from the origin of the event, for a band-passfiltered seismogram at a central frequency f, isrelated to the attenuation parameter Q by thefollowing equation:pattern, is the geometrical spreadingparameter equal to 1.0, 0.5 and 0.75 for bodywaves, surface waves ore diffusive wavesrespectively (5), , is the quality factor ofcoda waves. As S-Coda waves are backscatteredbody waves, =1.0 and the equation above takesthe form:From above,can be determined from theslope b of the strait line of least-squaresregression between with , usingthe relation: ., is the coda source factor at frequency f,which is independent of time and radiationFigure 3. BB recordings for September 6, 2010 at 21:49 (GMT) earthquake, (M=5.5) ate NE Albania.AKTET Vol. IV, Nr 2, 2011 237