Mapping Sn wave attenuation tomography across the Eastern Nepal Himalaya: Insights from Two Station Method

Our study introduces Sn wave attenuation tomography model developed for the eastern Nepal Himalaya. The objective is to explore the complex upper mantle heterogeneity beneath this tectonically significant region. Employing a robust network comprising 155 seismic stations (operational under XF, XQ, and YL networks), we have carefully analyzed 113 regional seismic events captured through 3433 seismic waveforms. The interstation Q values were calculated utilizing the Two Station Method (TSM). Following this, the least‐squares orthogonal factor decomposition (LSQR) inversion technique was used to develop a detailed tomographic model for this region, illustrating the spatial variations in Sn wave quality factor (Sn Q) across the region. Our results revealed a prevalence of low Q values, ranging from 20 to 100 throughout the area. The central region of our study exhibits medium Q value ranging from around 100 to 300. Moreover, isolated pockets of exceptionally high Q values have been observed in the northwestern and southeastern parts of the region. The tomographic results of this study are in sync with previously reported high attenuation in and around this region. This study enhances our understanding of the upper mantle beneath the eastern Nepal Himalaya, providing valuable insights into the lithospheric architecture and geodynamics of the region, as well as Sn wave propagation dynamics.