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The quality factor of the medium, Q, as a measure of the energy loss of the seismic waves during their travel through the Earth, is significantly sensitive to temperature. This study proposes the evaluation of QS(z) models for the upper mantle beneath the Romanian territory, by valuating the thermal models available for the lithosphere.
The thermal structure of the main tectonic compartments in the investigated area have previously been estimated by 2 D thermal modelling simulating the main geodynamic processes affecting the lithospheric structures (sedimentation and erosion in the Transylvanian and Focani Depressions, magma eruption in the Neogene volcanic belt, convergence process in the Eastern Carpathians). Finite-elements and finite-differences computer codes to solve the heat transfer equation were used. Surface heat flow determinations and information on sedimentary cover structure and history, as well as information on crustal structure were used to constrain the models.
The result of this study consists of maps of the quality factor QS distribution at different depths in the upper mantle. The proposed method for evaluation of the QS(z) model allows a quantitative determination of contribution of temperature variations in the upper mantle on the lateral variability of anelastic attenuation of seismic waves. The anelastic attenuation variations controlled by temperature are analyzed and compared with attenuation characteristics of the seismic wave propagation process obtained in seismic investigations, with the final aim to point out the peculiarities of the deep structure of the upper mantle beneath the Romanian territory.
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