Sn Attenuation in Iran and Surrounding Areas

Previous studies have proposed a complex seismic attenuation structure across the Middle East. In order to improve the knowledge of the uppermost mantle in Iran and surrounding areas, we collected a large data set consisting of 16 years (1996-2011) of waveforms recorded by 305 permanent and temporary stations. The high frequency Sn phase is blocked for much of the northern Middle East therefore we have looked to identify low frequency Sn waveforms. We used a bandpass filter (0.1-0.5Hz) to identify efficient longer period Sn phases. In order to determine Sn Q we applied a Two station Method (TSM) to eliminate the source effects. We have used the LSQR algorithm to tomographically map Sn attenuation tomography across the Iranian plateau. Our preliminary results indicate very low Q values within the central Iranian plateau down to less than 100. The pattern we observe is roughly consistent with tomographic Pn velocity models from prior studies. We also hope to compare our results with studies in the Northeastern Tibetan Plateau to have a better understanding of the propagation characteristics of long period Sn. In both the Tibetan and Iranian plateaus we appear high uppermost mantle attenuation beneath the highest topography indicating a thin and hot uppermost mantle.