Crustal structures beneath Mt. Baekdu (Changbai) volcano from receiver function and surface wave dispersion data

Shear wave velocity (Vs) structures beneath Mt. Baekdu volcano (MBV) and surrounding regions are estimated using receiver function (RF) analysis and transdimensional hierarchical Bayesian inversion of surface wave dispersion data. Stations near MBV exhibit complex RF waveforms characterized by pronounced negative signals between the direct P-wave and the Moho Ps phase, indicating local seismic anisotropy or dipping structures. Harmonic decomposition effectively reduced these negative peaks, highlighting significant anisotropy, though notable negative signals persisted directly beneath MBV, suggesting localized velocity-decreasing interfaces. Inverted shear wave velocity (Vs) models reveal a sharp and shallow crust–mantle transition (31–34 km depth) at stations farther from MBV, contrasting with a more gradual and deeper transition (35–40 km depth) beneath the volcano, reflecting crustal thickening (~ 40 km) and an extended velocity transition zone (~ 47–50 km depth) due to magmatic underplating and compositional differentiation. Localized high-Vs layers (~ 4.0 km/s) at shallow crustal depths (3–10 km) are interpreted as solidified mafic intrusions or horizontal sills, aligning closely with previously identified velocity-reducing zones. Lower crustal depths (> 25 km) beneath MBV feature localized relative Vs reductions (< 3.5 km/s), suggesting possibly thin layers of partial melt forming horizontal magma networks. These results emphasize the importance of accounting for seismic anisotropy and back-azimuthal dependencies in accurately modeling magmatic structures beneath active volcanoes.