Spectral Analysis of Shear Waves Acceleration Recorded in the Qeshm Earthquake (Persian Gulf) 2005 for Estimate Source Parameters and Environment Attenuation

The Qeshm earthquake in 27 November 2005 with magnitude ML=5. 6; mb=6. 2 occurred in Qeshm Island in the Persian Gulf and the main shock recorded in 11 strong motion acceleration building house research center (BHRC). In the study, the strong motion records are used to obtain an estimate of source parameters, high frequency attenuation and spectral decay parameter for 6 stations from 11 stations that is good S/N rate. The source parameters are obtained by fitting the data by a dislocation source model combined with an exponential model for the attenuation. The source parameter estimated is as follow: М0= 1. 13*1025±5*1024dyn - cm, r=6. 3±1. 17km, ∆u=26±1. 4cm∆ơ=21±1. 2bar, Td= 4. 3secAnd estimated moment magnitude МW=5. 95±0. 17 agree well with values obtained previously from Harvard University by CMT method. . The high frequency attenuation obtained using from amplitude spectral method that can be written as A (f, r) =G (r). e-חrf/Qβ that here G (r) is geometrical spreading. Estimates of path averaged crustal shear wave quality factors give results in the range between 60 - 367, and mean of spectral decay parameters for two horizontal components in the ranges between 0. 08 - 0. 12 sec.