Surface wave attenuation beneath the Himalaya-Tibet region constrained by fundamental mode of Rayleigh wave from the Hi-CLIMB dataset

Abstract

This study investigates Rayleigh wave group velocity and surface wave attenuation coefficients in the Himalaya-Tibet region using seismograms from 16 earthquakes recorded along the Hi-CLIMB network. The observed amplitude variations reveal a decreasing trend with distance, attributed to geometrical spreading, source radiation, wavefield scattering, and intrinsic attenuation. Attenuation coefficients range from 0.00167 km⁻¹ to 0.00039 km⁻¹ across the study area, while Rayleigh wave group velocities vary from 2.5 to 3.2 km/s for periods between 5 and 40 s. A strong frequency dependency in attenuation is observed, with attenuation coefficients peaking at shorter periods, consistent with similar trends reported in other tectonically active regions. Comparisons with global tectonic regions reveal higher attenuation beneath the study area, indicating low Q (41–82) values associated with mechanically weak, partially melted crust. The attenuation model suggests intrinsic attenuation as the dominant mechanism, though scattering effects cannot be ignored due to the region's structural complexity. Understanding these attenuation characteristics helps in interpreting seismic data and developing accurate ground motion prediction models, which are crucial for infrastructure resilience and early warning systems in this seismically active region. This, in turn, enhances seismic monitoring capabilities.