Estimation of source parameters, attenuation and spectral decay parameter by spectral method from recorded accelerograms during the Bam earthquake (2003)


1 Institute of Geophysics, University of Tehran, P.O. Box 14155-6466, Tehran, Iran

2 International Institute of Earthquake Engineering and Seismology, P. O. Box 19395-3913 Tehran, Iran


The Bam earthquake on 26 December, 2003 with a magnitude (Ms=6.8; mb=6) in southeastern Iran occurred in a populated area, and the main shock recorded in 23 strong motion acceleration building house research center (BHRC).
In this study, strong motion records are used to obtain an estimate of source parameters, high frequency attenuation and spectral decay parameter for 9 stations from 22 stations that have S/N rate good.
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 here
 and estimated moment magnitude  agree well with values obtained previously from Harvard university by the CMT method.
The high frequency attenuation obtained by used from the Amplitude spectral method that can be written as
Where  is geometrical spreading.
Estimates of path averaged crustal shear wave quality factors give results in the range 77 to 730, and mean of spectral decay parameters kappa= 0.08 sec for two horizontal components