Assimilation of seismic attenuation model of NW Himalaya and its surrounding region

• Seismic attenuation in the NW Himalaya using 2,716 earthquakes between 2008 and 2015. • A depth-dependent increase in Q c with frequency and lapse time. • The Tethys Himalaya shows the highest attenuation and the Higher Himalaya the lowest. • These findings enhance understanding of geotectonic segmentation. In this study, we analyze the seismic attenuation characteristics of the Northwest Himalaya and adjacent regions using a dataset of 2,716 earthquakes (2.5 ≤ Mw ≤ 5.0) recorded from 2008 to 2015 by a network of 30 broadband seismographs. The single backscattering model was applied to estimate the quality factor of coda waves ( Q c ) across three lapse time windows (LTWs) at varying frequencies. Our results reveal that Q c increases with both frequency and LTW, suggesting a depth-dependent nature of seismic attenuation in the region. The average attenuation relationships for Q c , Q α and Q β across the Northwest Himalaya are determined as follows for LTWs of 20, 30, and 40 seconds, respectively: Q c = (74 ± 14) f (1.27 ± 0.06) , Q c = (103 ± 26) f (1.16 ± 0.08) , and Q c = (140 ± 41) f (1.10 ± 0.09) . Our findings reveal significant variability in Q c , Q α and Q β across the Tethys (TH), High (HH), Lesser (LH), and Shiwalik (SH) Himalaya regions, as well as the adjacent Indo-Gangetic Plains (IGP), with this variability strongly linked to structural heterogeneity and seismogenic processes in each region. We further establish attenuation relations for distinct tectonic units, observing the following hierarchy: [ Q α,β,c −1 (HH) < Q α,β,c −1 (SH) < Q α,β,c −1 (IGP) < Q α,β,c −1 (LH) < Q α,β,c −1 (TH)]. The Tethys Himalaya exhibits the high attenuation, likely due to its sedimentary structure, while the Higher Himalaya shows the low attenuation. These insights into attenuation characteristics across geotectonic segments in the Northwest Himalaya contribute to a more comprehensive seismic hazard assessment for the region.