Coda Q in the Qeshm Island, South Iran Using Aftershocks of the Qeshm Earthquake of November 27, 2005

Qc-estimates of Qeshm Island in East southern part of Zagros have been obtained by using the aftershock data of Qeshm earthquake of November 27, 2005 recorded within an epicentral distance of 100 km. More than 829 earthquakes recorded by local temporary network consist 16 short period station installed after a week after main shock for ~10 weak. The coda quality factor, Qc, was estimated using the single backscattering model in frequency bands of 0.5–24 Hz. In this research, lateral and vertical variation of Qc in the Qeshm Island are studied. It is observed that in the Qeshm Island there is absence of significant lateral variation in Qc. To investigate the attenuation variation with depth, Qc value was calculated for six lapse times (5, 10, 15 . . . 30s). The average frequency relation for this region is Qc = 36 ± 1.2f 0.94±0.039 at 5 sec lapse time window length and Qc=110± 1.8f 0.88 ±0.09 at 30 sec lapse time window length. It is observed that Qc increases with depth. However, the rate of increase of Qc with depth is not uniform in our study area. Beneath Qeshm Island the rate of increase of Qc is greater at depths less than ~40 km compared to that at larger depths indicating the existence of a low attenuation anomalous structure under the ~40 km depth which may correlated with Moho depth in this region.