Abstract :
The occurrence of the western Iran earthquake of 31 March 2006 provided an important opportunity to study the source properties of earthquakes in this region. Although moderate in size (M L = 6.1, IIEES), this earthquake was the largest to have occurred in the region since the deployment of the Global Digital Seismograph Network. The far-field data determination of body wave (P) spectra, interpreted in terms of the circular seismic source model, are used to estimate the parameters seismic moment (Mo), corner frequency (fa) , source radius (r) and stress drop ((DELTA)(SIGMA)). P waves recorded at teleseismic distances can be obtained from stations of this network that are flat to displacement, in a frequency range of 0.19 to 0.32 Hz. The average seismic moment (Mo = 14.92 x 10^19 N-M) and source radius (r = 9281 m) were calculated from the long period spectral levels, which were corrected for the radiation pattern of a double couple point source. In addition, the stress drops ((DELTA)(SIGMA) = 87 x 10^6 N/m^2 ) ofthis event have been calculated by using an average seismic moment and source radius. Additional errors in the stress drop determination are produced by uncertainty in the seismic moment. Scatter in the seismic moment values is caused by such factors as site condition and errors in the radiation pattern.
