Publication Date:
2011-08-01
Description:
A seismic attenuation map of regional phase Pg is constructed for the northern Middle East using two-station frequency-dependent Q measurements and seismic attenuation tomography. Pg is widely used in source discrimination, but its attenuation behavior is not well understood. We investigate the functional form of the geometrical spreading of Pg for both uniform and more complex seismic velocity structures. We find that there is significant trade-off between attenuation and geometrical spreading of Pg, and we quantify this trade-off to interpret the observed Pg attenuation in the Middle East. The northern Middle East attenuation tomographic images show significant lateral Q (sub Pg) variations, which may be caused by lateral variations of crustal rheology if intrinsic attenuation dominates the seismic attenuation mechanism of this region. We observe very large variations in the Q (sub Pg) model, such as low Q (sub Pg) within the Anatolian plate and high Q (sub Pg) within much of the stable Arabian plate. The low Q (sub Pg) anomalies generally coincide with active fault systems or Quaternary volcanisms. In order to perform a systematic comparison with Lg propagation, we have also updated the Q (sub Lg) map of Zor et al. (2007). These two new maps provide estimates for crustal Q (sub alpha ) (Pg) and Q (sub beta ) (Lg) for the northern Middle East.
Print ISSN:
0037-1106
Electronic ISSN:
1943-3573
Topics:
Geosciences
,
Physics
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