The Firozabad-Kojour earthquake occurred on May 28, 2004 with an estimated magnitude of Mw=6.2, 60 Km north of Tehran. The main shock was recorded at 145 accelerograph stations which were installed by Building House Research Center (BHRC).
The strong motion records have been used to estimate attenuation of coda wave by using the single back scattering method (Aki, 1975).
The frequency dependence attenuation has been obtained in the Alborz according to four regions introduced by Tchalenko (1974) as follow:
1. Northwest Qc=92×f 1.14
2. Northeast Qc=188×f 0.79
3. Southwest Qc=157.5×f 0.93
4. Southeast Qc=132.5×f 0.87
for recorded stations of main shock and in frequency range of f=1~32Hz respectively, and studied manner changes Q-1 in difference stations and relation of tectonic and seismtectonic