Unveiling the seismic attenuation characteristics in the mantle beneath Southeast Asia: Insights into mantle dynamics and tectonic processes

In this paper, we analyze the Q value characteristics of the mantle beneath Southeast Asia (SE) using multiple ScS and sScS phases recorded at 78 seismic stations. The seismic attenuation in the mantle beneath the East Vietnam Sea (EVS) and the surroundings has been examined by applying the spectral ratio method to the multiple ScS₃/ScS₂ and sScS₃/sScS₂ phases recorded at seismic broadband stations surrounding the EVS region. The estimated average Q values for the EVS region for the ScS and sScS are 71.7 ± 49.1 and 86.0 ± 54.8 respectively, which are relatively low and fall within the range of volcanic active regions suggesting a relatively hot mantle beneath, which may reflect the spreading process of the EVS. Moreover, the Q values exhibit strong lateral variation based on the ray path propagating through different tectonic structures. Compared with the seismic tomography models and thermal structure of the region, the low Q value is observed along the ray paths that bounce regions with mantle wedge melting and subduction process present. In contrast, the high Q value of some source-station pairs might be explained by the low temperature of the shallow part of the upper mantle in the EVS central, suggesting the cessation of the spreading process in the Miocene.